NK1.1+ T cell receptor-alpha/beta+ cells: new clues to their origin, specificity, and function

IL-12-Mediated NKRP1A Up-Regulation and Consequent Enhancement of Endothelial Transmigration of Vδ2+ TCRγδ+ T Lymphocytes from Healthy Donors and Multiple Sclerosis Patients

γδ T lymphocytes are thought to play a role in the pathogenesis of multiple sclerosis (MS) contributing to demyelinization and fibrosis in the central nervous system. In this study, we show that, in MS patients with active disease, the percentage of circulating Vδ2+ γδ T cells coexpressing NKRP1A is significantly increased compared with healthy donors. Vδ2+ and Vδ1+ T cells were sorted from MS patients and healthy volunteers and cloned. At variance with Vδ1+ clones, all Vδ2+ clones expressed NKRP1A, which was strongly up-regulated upon culture with IL-12; this effect was neutralized by specific anti-IL-12 Abs. No up-regulation of NKRP1A by IL-12 was noted on Vδ1+ clones. RNase protection assay showed that IL-12R β2 subunit transcript was significantly less represented in Vδ1+ than Vδ2+ clones. This finding may explain the different effect exerted by IL-12 on these clones. In transendothelial migration assays, Vδ2+ NKRP1A+ clones migrated more effectively than Vδ1+ clones, and this migratory potential was enhanced following culture with IL-12. Migration was strongly inhibited by the F(ab′)2 of an anti-NKRP1A Ab, suggesting that this lectin is involved in the migration process. We also show that, in freshly isolated PBMC from MS patients, the migrated population was enriched for Vδ2+ NKRP1A+ cells. We conclude that the expression of NKRP1A on Vδ2+ cells is associated with increased ability to migrate across the vascular endothelium and that this phenomenon may be regulated by IL-12 present in the microenvironment.

Cutting Edge: LFA-1 Is Required for Liver NK1.1+TCRαβ+ Cell Development: Evidence That Liver NK1.1+TCRαβ+ Cells Originate from Multiple Pathways

Using mice deficient for LFA-1, CD44, and ICAM-1, we examined the role of these adhesion molecules in NK1.1+TCRαβ+ (NKT) cell development. Although no defect in NKT cell development was observed in CD44−/− and ICAM-1−/− mice, a dramatic reduction of liver NKT cells was observed in LFA-1−/− mice. Normal numbers of NKT cells were present in other lymphoid organs in LFA-1−/− mice. When LFA-1−/− splenocytes were injected i.v. into wild-type mice, the frequency of NKT cells among donor-derived cells in the recipient liver was normal. In contrast, when LFA-1−/− bone marrow (BM) cells were injected i.v. into irradiated wild-type mice, the frequency of liver NKT cells was significantly lower than that of mice injected with wild-type BM cells. Collectively, these data indicate that LFA-1 is required for the development of liver NKT cells, rather than the migration to and/or subsequent establishment of mature NKT cells in the liver.

Abundance of NKT cells in the salivary glands but absence thereof in the liver and thymus of aly/aly mice with Sjögren syndrome

It is known that ALY/Nsc Jcl-aly/aly (aly/aly) mice that congenitally lack lymph nodes fall victim to Sjögren syndrome as a function of age. We investigated how TCRint cells of extrathymic origin and TCRhigh cells of thymic origin are distributed in various organs of these mice. Although the distribution of T-cell subsets was not different between control aly/+ and aly/aly mice in youth in any of the tested organs, the proportion of TCRint cells in the liver and spleen of aly/aly mice increased with aging. Usually, TCRint cells in the liver comprise a half-and-half mixture of a NK1. 1(+) subset (i.e., NKT cells) and a NK1.1(-) subset. In constrast, almost all expanding TCRint cells in various immune organs of aly/aly mice were found to be NK1.1(-). A large proportion of lymphocytes, including NK cells and TCRint cells, were also present in the salivary glands of aly/aly mice. Interestingly, these TCRint cells in the salivary glands contained an NK1.1(+) subset (i.e., NKT cells) that used an invariant chain of Valpha14Jalpha281 for TCRalphabeta (>50%). Moreover, gammadeltaT cells that used Vgamma 1, 2, 4/Vdelta 1, 4, 6 mRNAs, different from those of gammadeltaT cells in the liver and intestine, were abundant. Possibly reflecting the in situ generation of these T cells in the salivary glands, the expression of RAG-2 mRNA was evident by the RT-RCR method. These results suggest that (i) inflammatory lymphocytes that evoke Sjögren syndrome in aly/aly mice are NK cells or TCRint cells (both NK1.1(+) and NK1.1(-) subsets) and (ii) TCRint cells in the salivary glands might be generated in situ.

Mechanisms involved in graft-versus-host disease induced by the disparity of minor histocompatibility M1s antigens

In this study we investigated which type of T cells: high T-cell receptor (TCRhigh, cells of thymic origin) or intermediate TCR (TCRint, cells of extrathymic origin), expanded in the liver and other organs, resulting in the induction of graft-versus-host disease (GVHD) with minor lymphocyte stimulating (M1s) disparity. When 6.5 Gy-irradiated BALB/c (H-2d M1s-1b2a) mice were injected with interleukin-2 receptor beta-chain(-) (IL-2Rbeta(-)) CD3high cells purified from the spleen of B10.D2 (H-2d M1s-1b2b) mice, IL-2Rbeta(+)CD3high cells expanded in the liver and other organs of recipient mice. The majority of these cells were found to be IL-2Ralpha(-)Mel-14(-)CD4(+)Vbeta3(+) in GVHD mice. The CDR3 region in their TCR-alphabeta (i.e. N-Dbeta-N) was polyclonal, although there were skewed usages of Vbeta3 and Jbeta2.4. The majority of cells were confirmed to be of donor origin by the individual discrimination method, namely, they originated from isolated IL-2Rbeta(-)CD3high cells. Interestingly, these T cells lacked cytotoxicity against both a natural killer (NK)-sensitive target and thymocytes with M1s disparity and nondisparity. Another important finding was that activated granulocytes expanded at generalized sites in GVHD mice. The present results raise the possibility that M1s disparity is mainly recognized by TCRhigh cells with unique properties but that direct effector cells that induce GVHD might not be such T cells but rather accompanied granulocytes.

Clonal dissemination of T-lymphocytes in scid mice from familial hemophagocytic lymphohistiocytosis

BACKGROUND

Although familial hemophagocytic lymphohistiocytosis (FHL) has been considered a disorder of T-cell dysfunction, there is no evidence of the clonal origin of T-cells in this disease.

PROCEDURE

We engrafted mononuclear cells (MNCs) from five FHL patients into scid mice and examined the infiltration of human cells in mouse organs. The characterization of human cells that infiltrated in the mouse organs was then performed.

RESULTS

A diffuse infiltration of human lymphoid cells was detected in scid mice treated with 1 x 10(6) MNCs from one of the five patients. These cells were positive for HLA-DR and CD3, but negative for CD4, CD8, CD20, and CD68, suggesting the infiltration of double negative (DN) T-cells. The MNCs from the other four patients induced murine lymphoma-like disease; T-cell lymphoma in one and lymphoma of unknown origin in three. The characterization of these human DN T-cells was performed. The analysis of the Vbeta repertoire showed no preferential usage of the Vbeta family in MNCs, while the dominant expression of Vbeta13 was detected in T-cells infiltrating in the spleen and lung. A Jbeta analysis showed the restricted usage of Jbeta1.2 for Vbeta13 in these cells, and the clonality of Vbeta13-Jbeta1.2 fragment was confirmed by a single-strand confirmation polymorphism analysis. The analysis of the Valpha repertoire showed that Valpha24 was exclusively used in these DN T-cells, but no usage of JalphaQ for Valpha24 was observed.

CONCLUSIONS

A clonal expansion of T-cells was induced in scid mice by the engraftment of MNCs from an FHL patient. The infiltration of DN alphabeta T-cells bearing invariant Valpha24 T-cell receptor in mouse organs may provide a useful clue to the pathogenesis of FHL. In the patients whose MNCs induced murine lymphoma-like disease, some cytokines or unknown factors that stimulate the growth and the tumorigenicity of murine lymphocytes might be produced by the MNCs engrafted in scid mice. Further study is needed to confirm the validity of our experimental approach and the findings observed in scid mice by using more FHL samples.

Liver-associated lymphocytes expressing NK1.1 are essential for oral immune tolerance induction in a murine model

Oral tolerance is the induction of immunological hyporesponsiveness towards orally administered antigens. Tolerance initiation involves induction of anti-inflammatory (Th2) lymphocytes, with downregulation of pro-inflammatory (Th1) lymphocytes. The liver was previously shown to play a critical role in oral tolerance induction. The aim of the present study was to test whether liver-associated-lymphocytes expressing the NK1.1 marker (NK1.1+ LAL) are substantial for induction of oral tolerance in an experimental colitis model. Colitis was induced in C57 mice by intracolonic instillation of trinitrobenzensulfonic acid (TNBS). Mice received five oral doses of colonic proteins extracted from TNBS-colitis colonic wall. Anti-NK1.1 monoclonal antibodies were injected before tolerance induction. Colitis was assessed by standard clinical, macroscopic, and microscopic scores. Serum IFN-gamma, TGF-beta1, and IL4 levels were measured by enzyme-linked immunosorbent assay. To evaluate the role of NK1.1+ LAL in keeping the balance between immunogenic and tolerogenic subsets of cells, we tested whether peripheral lymphocytes harvested from tolerized and NK1.1-depleted nontolerized mice can adoptively transfer the tolerance into naive irradiated rats. Depletion of NK1.1+ LAL prevented immune tolerance induction in the experimental colitis model. NK1.1+ LAL-depleted nontolerized mice, disclosed severe clinical, macroscopic, and microscopic parameters of colitis. These mice had significantly lower TGF-beta1, IL4, and higher IFN-gamma serum levels, and their lymphocytes failed to transfer the tolerance into naive animals. In contrast, the feeding of colitis-extracted proteins, without NK1.1+ LAL depletion, markedly alleviated the disease. Tolerized mice had higher IL4 and TGF-beta1 and lower IFN-gamma serum levels, and adoptive transfer of their suppressor splenocytes markedly alleviated colitis in naive recipients. NK1.1+ LAL plays a critical role in oral tolerance induction. Depletion of this subset of LAL prevents a shift from Th1 to a Th2 type of immune response, hindering the ability to induce immune tolerance.

Marking IL-4-producing cells by knock-in of the IL-4 gene

IL-4 is a cytokine which can be expressed by a number of cell types including Th2 cells, mast cells and a population of CD4+ NK1.1+ NK T cells. Although phenotypic markers exist for identifying each of these cell types, there is at present no known cell surface marker common to all IL-4-producing cells. Using gene targeting in embryonic stem cells, we have modified the IL-4 locus by knock-in of a transmembrane domain to generate mice that express a membrane-bound form of IL-4 (mIL-4). Flow cytometry using an IL-4-specific mAb allowed the detection of IL-secreting Th2 cells, mast cells and NK T cells from mIL-4 mice. Furthermore, the analysis of immune responses in mIL-4 mice following immunization with anti-CD3 and anti-IgD has allowed us to identify distinct subpopulations of IL-4-producing NK T cells. Thus, the expression of IL-4 in a membrane-bound form provides a novel method for the identification and characterization of IL-4-producing cells.

MHC Class II-Dependent NK1.1+ γδ T Cells Are Induced in Mice by Salmonella Infection

We observed the emergence of a novel population of γδ T cells expressing NK1.1 Ag in the peritoneal cavity of mice infected with Salmonella choleraesuis. The NK1.1+γδ T cells accounted for approximately 20% of all γδ T cells emerging in the peritoneal cavity of C57BL/6 mice and expressed preferentially rearranged Vγ4-Jγ1 and Vδ6.3-Dδ1-Dδ2-Jδ1 genes with N diversity. The γδ T cells proliferated vigorously in response to PHA-treated spleen cells and produced IFN-γ in the culture supernatant. However, spleen cells from Aβb-deficient mice were unable to stimulate the γδ T cells. Furthermore, the NK1.1+γδ T cells were stimulated not only by Chinese hamster ovary (CHO) cells expressing wild-type IAb but also by those expressing IAb/Eα52-68 or IAb/pigeon cytochrome c-derived analogue peptide complex. These proliferation activities were inhibited by mAb specific for IAb chain. Consistent with these findings, the emergence of NK1.1+γδ T cells was reduced in the peritoneal cavity of Aβb-deficient mice after Salmonella infection, whereas NK1.1+γδ T cells were rather abundant in the peritoneal cavity of Salmonella-infected β2m-deficient mice. Moreover, the NK1.1+γδ T cells were easily identified in the thymus of β2m-deficient but not Aβb-deficient mice. Our results indicated that MHC class II expression is essential for development and activation of NK1.1+γδ T cells in the thymus and the periphery.

Natural T cells in the human liver: cytotoxic lymphocytes with dual T cell and natural killer cell phenotype and function are phenotypically heterogenous and include Valpha24-JalphaQ and gammadelta T cell receptor bearing cells

The adult liver contains lymphocytes with a unique phenotypic distribution compared to blood and other organs. We have characterized a human lymphocyte population that exhibits dual T cell and natural killer (NK) cell phenotype and function, denoted natural T (NT) cells, in nine normal adult liver specimens. Flow cytometry revealed that up to 55% (mean 27%) of hepatic (but <6% of peripheral) CD3+ lymphocytes expressed CD56, CD161 and/or one or more of the killer inhibitory receptors (KIR) p58.1, p58.2, p70 and CD94. NK function was attributed to the CD3+CD56+ cells by the demonstration that hepatic, but not peripheral, CD3+ lymphocytes could be induced to lyse NK-sensitive K562 target cells, while CD56- cells from both compartments could not. Three color flow cytometric analysis of fresh hepatic cells indicated that CD3+CD56+ NT cells can be either CD8+, CD4+ or CD4 CD8-, they express alphabeta or gammadelta T cell receptors (TCR) and CD161 and KIRs, but rarely CD16. Hepatic NT cells predominantly express the mature/activated CD45RO and CD56dim phenotypes. Analysis of mRNA production by isolated NT cells indicated a preferential usage of the invariant CD1-restricted Valpha24-JalphaQ TCR. The presence of such large numbers of chronically activated NT cells provides compelling evidence that the liver has unique immunoregulatory functions.

Natural killer activity in a medium-term multi-organ bioassay for carcinogenesis

Natural killer (NK) cell activity was evaluated after the initiation and promotion steps in a medium-term multi-organ bioassay for carcinogenesis. NK cell activity was assessed in vitro by Cr51 release assay at the 4th and 30th weeks of the experiment. Male Wistar rats were sequentially initiated with N-diethylnitrosamine (DEN i.p.), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN drinking water), N-methyl-N-nitrosourea (MNU i.p.), dihydroxy-di-N-propylnitrosamine (DHPN drinking water) and N,N'-dimethylhydrazine (DMH s.c.) at subcarcinogenic doses for 4 weeks (DMBDD initiation). One group was evaluated at the 4th week and the other was maintained without any further treatment until the 30th week. Two initiated groups were exposed through the diet to 2-acetylaminofluorene (2-AAF) or phenobarbital (PB), from the 6th until the 30th week. Five additional groups were studied to evaluate the effects of each initiator on NK activity. All groups submitted to initiation only, initiation plus promotion, or promotion only, developed significantly more preneoplastic lesions than the untreated control group. The main target organs for tumor development in the initiated animals were the liver and the colon, irrespective of treatment with 2-AAF or PB. NK cell activity was not affected by exposure to genotoxic carcinogens after initiation, at the 4th week. Treatments only with PB or 2-AAF did not change NK cell activity. However, decreased NK cell activity was registered in the group only initiated with DMBDD and in the group given DMBDD+2-AAF. This late depression of NK cell activity at the 30th week could be related to the production of suppressing molecules by the tumor cells.

Characterization of NK cells and extrathymic T cells generated in the liver of irradiated mice with a liver shield

We previously reported that c-kit+ stem cells which give rise to extrathymic T cells are present in the liver of adult mice. Further characterization of extrathymic T cells in the liver of adult mice is conducted here. When mice with a liver shield were lethally (9.5 Gy) irradiated, all mice survived. All tested organs showed a distribution pattern of hepatic lymphocytes on day 7. The distribution pattern in the liver was characterized by an abundance of NK (CD3- IL-2Rbeta+) and extrathymic T cells (CD3int IL-2Rbeta+) before and after irradiation. To determine their function, post-irradiation allogeneic bone marrow transplantation (BMT) was performed in mice with or without a liver shield. Allogeneic BM cells were rejected in mice with a liver shield and specific activation of CD8+ CD3int IL-2Rbeta+ cells was induced. At that time, potent cytotoxicity of liver mononuclear cells (MNC) against allogeneic thymocytes was induced. Both NK1.1+ and NK1.1- subsets of CD3int cells expanded in these mice. An in vivo elimination experiment of the subsets indicated that the NK1.1+ subset of CD3int cells (i.e. NK T cells) was much more associated with the rejection of allogeneic BM cells. However, even after the elimination of NK T cells, allogeneic BM cells were rejected. In this case, granulocytes expanded in parallel with NK1.1- subsets. Granulocytes may also be associated with the rejection of allogeneic BM cells. These results suggest that the liver is an important haematopoietic organ even in adult life.

A population of CD62Llow Nk1.1- CD4+ T cells that resembles NK1.1+ CD4+ T cells

In MHC class II-/- C57BL/6 (II-/-) mouse spleen, a small population of CD4+ T cells is present of which NK1.1+ CD4+ (NK) T cells comprise 40 to 45%. We report here that many of the NK1.1- CD4+ T cells derived from II-/- mice are also NK T cells. They produce large amounts of IL-4 in response to anti-CD3 ligation and do so without any requirement for the presence of IL-4 in the priming culture, a property characteristic of NK T cells. Their IFN-gamma production is large and is enhanced by IL-12. In addition, II-/- NK1.1- CD4+ T cells produce IL-4 as a result of culture with L cells expressing murine CD1 (L-CD1). We report that CD49b, a component of integrin VLA-2, is expressed on the majority of both NK1.1+ and NK1.1- NK T cells. NK1.1- NK T cells also exist in wild-type C57BL/6 mice. Evidence supporting this is that Vbeta8 usage by CD62Llow NK1.1- CD4+ T cells was approximately 5% higher than that by CD62Lhigh CD4+ T cells in wild-type mice in keeping with the estimated proportion of NK1.1- NK T cells in the CD62Llow population. CD62Llow CD4+ T cells from beta2-m(-/-) mice, which lack NK T cells, showed no increase in Vbeta8 usage. When activated by anti-CD3 or L-CD1, CD62Llow NK1.1- CD4+ T cells from conventional but not beta2-m(-/-) and CD1-/- mice produce IL-4 in a manner indistinguishable from II-/- NK1.1- CD4+ T cells. NK1.1- NK T cells in normal mouse spleens are approximately as numerous as NK1.1+ NK T cells.

CD161 (NKR-P1A) costimulation of CD1d-dependent activation of human T cells expressing invariant V alpha 24 J alpha Q T cell receptor alpha chains

A population of human T cells expressing an invariant V alpha 24 J alpha Q T cell antigen receptor (TCR) alpha chain and high levels of CD161 (NKR-P1A) appears to play an immunoregulatory role through production of both T helper (Th) type 1 and Th2 cytokines. Unlike other CD161(+) T cells, the major histocompatibility complex-like nonpolymorphic CD1d molecule is the target for the TCR expressed by these T cells (V alpha 24(invt) T cells) and by the homologous murine NK1 (NKR-P1C)+ T cell population. In this report, CD161 was shown to act as a specific costimulatory molecule for TCR-mediated proliferation and cytokine secretion by V alpha 24(invt) T cells. However, in contrast to results in the mouse, ligation of CD161 in the absence of TCR stimulation did not result in V alpha 24(invt) T cell activation, and costimulation through CD161 did not cause polarization of the cytokine secretion pattern. CD161 monoclonal antibodies specifically inhibited V alpha 24(invt) T cell proliferation and cytokine secretion in response to CD1d+ target cells, demonstrating a physiological accessory molecule function for CD161. However, CD1d-restricted target cell lysis by activated V alpha 24(invt) T cells, which involved a granule-mediated exocytotic mechanism, was CD161-independent. In further contrast to the mouse, the signaling pathway involved in V alpha 24(invt) T cell costimulation through CD161 did not appear to involve stable association with tyrosine kinase p56(Lck). These results demonstrate a role for CD161 as a novel costimulatory molecule for TCR-mediated recognition of CD1d by human V alpha 24(invt) T cells.

Rapid death and regeneration of NKT cells in anti-CD3epsilon- or IL-12-treated mice: a major role for bone marrow in NKT cell homeostasis

Natural killer T (NKT) cells express a T cell receptor (TCR) and markers common to NK cells, including NK1.1. In vivo, NKT cells are triggered by anti-CD3epsilon MAb to rapidly produce large amounts of IL-4 and by IL-12 to reject tumors. We show here that anti-CD3epsilon MAb treatment rapidly depletes the liver (and partially the spleen) of NKT cells and that homeostasis is achieved 1 to 2 days later via NKT cell proliferation that occurs mainly in bone marrow. Similar results were obtained in mice treated with IL-12. Collectively, our data demonstrate that peripheral NKT cells are highly sensitive to activation-induced cell death and that bone marrow plays a major role in restoring NKT cell homeostasis.

IL-18 Augments Perforin-Dependent Cytotoxicity of Liver NK-T Cells

The liver contains abundant cytotoxic cells, including NK-T cells, NK cells, and CTLs. However, the regulation of this cytotoxicity is not fully understood. In this study, we investigated the effect of a recently described cytokine, IL-18, which is present in large quantities in the liver, on the cytotoxicity of intrahepatic lymphocyte subpopulations. This effect of IL-18 was assessed by assaying the in vitro cytotoxicity of purified NK-T, NK, and T cells against a CD95- and perforin-sensitive T cell line, Jurkat. The results show that IL-18 enhances the killing activity of liver NK-T cells by a CD95-independent, perforin-dependent pathway. IL-18 also augments liver NK cell activity, but the exact mechanisms of this killing remain to be elucidated. Finally, the augmentation of the killing activities of liver NK-T and NK cells by IL-18 is not due to soluble TNF-α, because none of these cell populations had detectable TNF-α production.

Modulation of Ly49A receptors on mature cells to changes in major histocompatibility complex class I molecules

The expression of murine Ly49 receptors on natural killer (NK) cells and NK1.1+ T cells is believed to prevent these cells from responding against normal self-tissues. In this report we investigated whether the expression level of Ly49A was fixed on mature cells or if it could be adapted as the major histocompatibility complex (MHC) class I environment changed in vivo. By transferring peripheral T cells from Ly49A transgenic mice into BALB/c nude/nude and B6 nude/nude mice, we demonstrated that mature cells modulate their Ly49A receptor expression relative to the in vivo MHC class I environment. These results indicated that the expression of the inhibitory Ly49A receptor is not permanently fixed during a maturation and/or education process but rather is adapted to MHC class I changes on the surrounding cells.

Rat NKR-P1+ CD3+ T cells: selective proliferation in interleukin-2, diverse T-cell-receptor-Vbeta repertoire and polarized interferon-gamma expression

Cells expressing markers of both natural killer and T lymphocytes (NK T cells) in humans and mice express a restricted T-cell receptor (TCR) repertoire, are of CD4- CD8- or CD4+ CD8- phenotype, and upon anti-CD3 stimulation secrete large amounts of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma). NK T cells may be the primary source of IL-4-promoting T helper type 2 (Th2) responses and/or they might be involved in regulating the balance between Th1- and Th2-type immune responses, and may consequently affect susceptibility to autoimmune diseases associated with a skewed Th phenotype. We show that rat NK T cells selectively proliferate to IL-2, and use this fact to analyse cytokine production by NK T cells in two rat strains differentially susceptible to Th1- or Th2-type autoimmune diseases. Analysis by reverse transcription-polymerase chain reaction revealed that, in contrast to mouse, rat NK T cells secrete exclusively IFN-gamma and not IL-4 after anti-CD3 stimulation, and use a wider TCR-Vbeta repertoire, suggesting that rat NK T cells are not essential for the development of Th2-type CD4+ T-cell responses.

Positive selection of extrathymically developed T cells by self-antigens

Most T cells develop through the thymus, where they undergo positive and negative selection. Some peripheral T cells are known to develop in the absence of thymus, but there is insufficient information about their selection. To analyze the selection of extrathymically developed T cells, we reconstituted thymectomized male or female recipient mice with bone marrow cells of mice transgenic for male H-Y antigen-specific T cell receptor (TCR). It was revealed that the T cells bearing self-antigen-specific TCR were not deleted in thymectomized male recipients. More importantly, the absence of H-Y antigen-specific T cells in thymectomized female recipients suggests positive selection of extrathymically developed T cells by the self-antigen. The extrathymically developed T cells in male mice expressed interleukin (IL)-2 receptor beta chain (IL-2Rbeta) and intermediate levels of CD3 (CD3(int)) but were natural killer cell (NK)1.1(-). They rapidly produced interferon gamma but not IL-4 after TCR cross-linking. Furthermore, a similar pattern of cytokine production was observed in CD3(int)IL-2Rbeta+NK1.1(-) cells in normal mice which have been shown to develop extrathymically. These results suggest that extrathymically developed CD3(int)IL-2Rbeta+NK1. 1(-) cells in normal mice are also positively selected by self-antigens.

Participation of NK1.1+ T cells in the rejection of lpr alphabetaT cells when bone marrow cells of lpr mice are transplanted into B6 mice

When C57BL/6 (B6) mice were irradiated (9 Gy) and received bone marrow (BM) cells of B6-lpr/lpr mouse origin (i.e., lpr-->B6), all mice died within 6 days. In the irradiated B6 mice, radioresistant CD3 IL-2Rbeta+ NK cells and IL-2Rbeta+ CD3int cells (i.e., CD3int cells of extrathymic origin) remained, especially in the liver. There were two subsets, NK1.1+ and NK1.1-, among the IL-2Rbeta+ CD3int cells. However, the NK1.1+ subset (i.e., NK1.1- T cells) was much more radioresistant, and the majority of CD3int cells belonged to this subset in irradiated mice. The expansion of lymphocytes from injected BM cells did not occur in the irradiated B6 mice. However, such expansion did take place in irradiated B6-lpr/lpr mice injected with both BM cells of B6-lpr/lpr and B6 origin. As a result, the mice subjected to BM cells survived. Irradiated B6 mice were treated in vivo with anti-NK1.1 mAb or anti-asialoGM1 antibody to eliminate NK cells alone or both NK cells and NK1.1+ T cells. When irradiated B6 mice were pretreated with anti-NK1.1 mAb, the mice could survive. These results suggest that intact NK1.1+ T cells of extrathymic origin may recognize abnormal BM cells with the lpr gene and inhibit the expansion of lymphocytes, including abnormal double-negative CD4 8 cells, in B6-lpr/lpr mice. To inhibit the expansion of lymphocytes, mechanisms other than Fas ligand/Fas molecules on extrathymic T cells may be responsible.

Intrathymic selection of NK1.1(+)alpha/beta T cell antigen receptor (TCR)+ cells in transgenic mice bearing TCR specific for chicken ovalbumin and restricted to I-Ad

Generation and negative selection of NK1.1(+)alpha/beta T cell receptor (TCR)+ thymocytes were analyzed using TCR-transgenic (B10. D2 x DO10)F1 and (C57BL/6 x DO10)F1 mice and Rag-1(-/-)/DO10 mice, which had been established by breeding and backcrossing between Rag-1(-/-) and DO10 mice. Almost all T cells from these mice were shown to bear Valpha13/Vbeta8.2 that is specific for chicken ovalbumin (cOVA) and restricted to I-Ad. A normal proportion of the NK1.1(+) Valpha13/Vbeta8.2(+) thymocytes was generated in these mice. However, the actual cell number of both NK1.1(+) and NK1.1(-) thymocytes in I-Ad/d mice (positive selecting background) was larger than that in I-Ab/d mice (negative selecting background). Markedly low but significant proportions of NK1.1(+) Valpha13/Vbeta8.2(+) cells were detected in the spleens from I-Ad/d and I-Ab/d mice. It was shown that the splenic NK1.1(+) T cells of the I-Ab/d mice were anergized against stimulation through TCR. When (B10.D2 x DO10)F1 and (C57BL/6 x DO10)F1 mice were given cOVA, extensive or intermediate elimination of NK1.1(+)alpha/betaTCR+ thymocytes was induced in I-Ad/d or I-Ab/d mice, respectively. However, the clonal elimination was not as complete as that seen in the major NK1.1(-) thymocyte population. The present findings indicate that normal generation of NK1.1(+)alpha/betaTCR+ thymocytes occurs in the absence of Valpha14-Jalpha281 and that substantial negative selection operates on the NK1.1(+)alpha/betaTCR+ cells.

Gammadelta T-cell precursor-derived CD4- CD8- alphabeta T cells retain gammadelta cell function

We have previously shown that some of the DN alphabeta+ T cells arising in TcR alpha-chain transgenic mice are of gammadelta T cell origin, based on phenotypic data and on their status of TcR gene rearrangements. In the present report we investigated the impact of alphabeta TcR expression on the functional programme of the mature gammadelta precursor-derived DN alphabeta+ T cells. Our results demonstrate that both their proliferative capacity and their cytokine production profile are similar to that of gammadelta T cells. Furthermore, both transgenic DN alphabeta+ T cells and DN gammadelta+ T cells up-regulate CD8alpha expression after activation, but, in contrast to CD4+ alphabeta T cells, are unable to induce proliferation of naive B cells. Thus, our results suggest that the effector functions of mature T cells are determined independently of the TcR isotype, probably at an early stage of differentiation, and thereby have important implications for current models of T-cell lineage commitment.

Developmentally regulated extinction of Ly-49 receptor expression permits maturation and selection of NK1.1+ T cells

Clonally distributed inhibitory receptors negatively regulate natural killer (NK) cell function via specific interactions with allelic forms of major histocompatibility complex (MHC) class I molecules. In the mouse, the Ly-49 family of inhibitory receptors is found not only on NK cells but also on a minor (NK1.1+) T cell subset. Using Ly-49 transgenic mice, we show here that the development of NK1.1+ T cells, in contrast to NK or conventional T cells, is impaired when their Ly-49 receptors engage self-MHC class I molecules. Impaired NK1.1+ T cell development in transgenic mice is associated with a failure to select the appropriate CD1-reactive T cell receptor repertoire. In normal mice, NK1.1+ T cell maturation is accompanied by extinction of Ly-49 receptor expression. Collectively, our data imply that developmentally regulated extinction of inhibitory MHC-specific receptors is required for normal NK1.1+ T cell maturation and selection.

The regulation of phenotype and function of human liver CD3+/CD56+ lymphocytes, and cells that also co-express CD8 by IL-2, IL-12 and anti-CD3 monoclonal antibody

The regulation of phenotype and function of human liver infiltrating lymphocytes (LIL) by in vitro culture with IL-2, IL-12 and anti-CD3 monoclonal antibodies (mAb) was investigated. The CD3+ LIL which express 50% less CD3 molecules per cell than peripheral blood T lymphocytes, exhibited a 6-fold reduction in proliferation when stimulated through the CD3 complex by anti-CD3 mAb. LIL freshly isolated or cultured in medium did not suppress MLR response, nor were they cytotoxic. However, treatment of the LIL cells with IL-2, IL-12 and anti-CD3 induced these cells to suppress autologous responding cells in MLR (ca. 70%) and to kill autologous or allogeneic cells. Low level cytotoxicity could be induced by cytokines IL-2, IL-12 or anti-CD3 alone. However, the development of optimum MLR suppression and cytotoxicity induction was dependent upon stimulation of the LIL cells through the CD3 complex. The co-expression of CD3 and CD56 on LIL was also up-regulated by anti-CD3 stimulation in the combination of IL-2 and IL-12. Most of the CD3+/CD56+ cells, also expressed CD8. After the magnetic bead separation procedure, the cytotoxic activity was found mainly in the CD3+/CD56+/CD8+ population. These results suggest that CD3+/CD56+/CD8+ cells can be expanded by stimulation through the TCR/CD3 complex in the presence of IL-2 and IL-12, which results in the suppression of autologous responding cells by a cytotoxic mechanism. The proliferative response of the CD3+/CD56+/CD8+ population was enhanced by the induction of CD1 molecules on the stimulating cells, and anti-CD1 mAb were able to block the response in a dose-dependent manner. The CD3+/CD56+/CD8+ cells were examined for cytokine production by flow cytometry. Cytokines IL-4, TNF-alpha, and IFN-gamma were produced by 91.7%, 29.2%, and 27.4% of the cells, respectively.

An allogeneic microenvironment influences the phenotype of intermediate T-cell receptor cells expanding in MRL-lpr/lpr mice

MRL-lpr/lpr (lpr) mice fall victim to autoimmune disease owing to a lymphoproliferative disorder mainly of double-negative (DN) CD4- CD8- alpha beta T cells expressing a low density of interleukin-2 receptor beta-chain (IL-2R beta). It was previously revealed that the lpr gene is a defective Fas gene, into which an early transposon (ETn) of retrovirus is transfected. As a result of the failure of apoptosis, intermediate T-cell receptor (TCR) cells (i.e. TCRint cells) with DN phenotype abnormally accumulate in the periphery of lpr mice. We investigated herein how these TCRint cells are selected in terms of CD4, CD8 and TCR in lpr mice. When a whole fraction of mononuclear cells (MNC) in various immune organs of lpr mice was injected into scid mice (allogeneic circumstance), CD8+ TCRint cells mainly expanded. They had a high density of IL-2R beta. This was true when bone marrow cells of lpr mice were injected into scid mice. On the other hand, when MNC of the spleen and bone marrow in lpr mice were injected into irradiated (9 Gy) lpr mice (syngeneic circumstance), the major expanding cells were DN TCRint cells expressing a low density of IL-2R beta. A cell-sorting experiment for purified fractions demonstrated that only CD8- cells reconstituted TCRint cells in scid mice. Namely, DN CD4- CD8- cells as well as CD4+ cells which once acquired the mature phenotype, no longer switched their phenotype. These results suggest that the phenotype of TCRint cells is influenced by the surrounding microenvironment.

A Critical Role for IL-4 in Regulating Disease Severity in Experimental Allergic Encephalomyelitis as Demonstrated in IL-4-Deficient C57BL/6 Mice and BALB/c Mice

Experimental allergic encephalomyelitis (EAE) is a T cell-mediated autoimmune disease of the central nervous system (CNS) that has served as the principal experimental model for multiple sclerosis (MS). Susceptibility to disease is thought to correlate with the ability to generate a Th1-type cytokine profile in myelin-responsive T cells, whereas T cells producing a Th2 cytokine pattern, in particular IL-4, are thought to be nonencephalitogenic and also to confer protection against a Th1-type response. However, recent studies using a variety of genetically engineered animals in which the genes for Th1-type cytokines and/or their receptors have been inactivated have called into question the Th1-Th2 paradigm in experimental allergic encephalomyelitis. In this report we have addressed the contribution of IL-4 to disease expression by studying two strains of mice, C57BL/6 and BALB/c, in which the gene for IL-4 has been inactivated. The IL-4-deficient C57BL/6 mice, and to a lesser extent the IL-4-deficient BALB/c mice, developed a more severe form of clinical disease, a more extensive pathologic involvement of the spinal cord, and an increased expression of proinflammatory cytokines in the CNS than their wild-type littermates. BALB/c and C57BL/6 mice showed a slightly different cytokine profile in the CNS. Both groups of animals recovered from the acute clinical episode in a time frame that was essentially identical to that found in the wild-type controls. We conclude that IL-4 plays an important role in modulating the severity of the encephalitogenic process, but does not by itself contribute to spontaneous remission from the disease.

Continuing observations on the regulatory effects of donor-specific bone marrow cell infusions and chimerism in kidney transplant recipients

BACKGROUND

Continued follow-up of a series of donor bone marrow cell (DBMC)-infused first cadaver renal transplant recipients is described (n=58), now at a 36-month actuarial time point postoperatively. Serial polymerase chain reaction-flow cytometry (PCR-Flow) and cellular immune assays of iliac crest bone marrow aspirates and peripheral blood have begun to be compared with concomitantly transplanted recipients of living-related donor (LRD) kidneys and donor marrow infusions given the same immunosuppressive regimen (n=16). There have also been comparisons (36 months) with 188 controls transplanted concomitantly, i.e., recipients of first cadaver kidney transplants, who did not receive bone marrow.

METHODS

Each group was given equivalent immunosuppressive regimens of OKT3 anti-T cell induction and maintenance tacrolimus, mycophenolate mofetil, and methylprednisolone. Actuarial patient and graft survival have been 96% and 93%, respectively, in the controls and 91% and 91%, respectively, in the DBMC-infused recipients. Trough levels of tacrolimus were significantly lower in the DBMC-infused group.

RESULTS

In PCR-Flow measurements, in peripheral blood up to 6 months postoperatively, there were higher levels of chimerism, i.e., in the total number of donor cells, as well as the donor CD3+ and CD34+ subsets in the LRD recipients administered DBMC infusions, compared with cadaver DBMC recipients, supporting the notion of a positive effect of histocompatibility on chimerism levels. In PCR-Flow measurements of recipient iliac crest bone marrow aspirates as in previous studies on peripheral blood, early acute rejection episodes (<1 month) were found to be associated with a later (6-14 months) decrease in donor cell lineage chimerism. However, a trend toward recovery of chimeric levels occurred by 21-28 months in a second iliac crest marrow aspirate 1 year after the first aspirate in the DBMC-infused recipients who experienced such early rejection episodes. This was in contrast to the controls in whom there were sustained low levels of iliac crest bone marrow chimerism at both the earlier and later intervals (i.e., no chimeric recovery), with 17/183 surviving controls progressing into chronic rejection. This has not yet been seen in the DBMC-infused group (0/54). In in vitro observations on cellular immune reactivity at 1 year postoperatively, decreased peripheral blood lymphocyte proliferative reactions were seen in response to phytohemagglutinin and Staph-A mitogens, as well as to cytomegalovirus and Epstein-Barr viral protein antigens in the DBMC-infused group versus the controls. Chronic immunosuppression did not seem to effect a vigorous in vitro inhibitory (regulatory) activity of bone marrow taken from these transplant recipients 2 years postoperatively in mixed lymphocyte culture and cell-mediated lympholysis reactions, using allogeneic responding cells from "normal" laboratory volunteers. Autologous peripheral blood lymphoproliferative responses to phytohemagglutinin and Staph-A mitogens, as well as to cytomegalovirus and Epstein-Barr virus protein antigens, were also regulated by either organ donor (non-immunosuppressed) bone marrow cells or by transplant recipient (immunosuppressed) bone marrow cells. What appeared to be disparate between the DBMC-infused and control groups (both immunosuppressed) was the trend for the (autologous) bone marrow suppressive effect on antiviral lymphoproliferative responses, to be stronger in the DBMC-infused group, who also had significantly (>one order of magnitude) higher levels of chimerism (P=0.01).

CONCLUSIONS

It is concluded that the establishment of a chimeric state in DBMC-infused recipients, albeit of relatively low magnitude (approximately 1% at 2 years in recipient iliac crest bone marrow), has had a definite regulatory effect on immune responses. These results, therefore, add weight to the "causal" horn of the dilemma as to whether donor cell chimerism is a cause or an effect of

Intermediate TCR cells can induce graft-versus-host disease after allogeneic bone marrow transplantation

Mice fall victim to GVHD when subjected to immunosuppressive treatment and injected with allogeneic bone marrow cells. A major population of cells associated with GVHD is known to be T cells. However, whether such T cells are of thymic or extrathymic origin is obscure. We applied two immunosuppressive conditions, 9 and 6.5 Gy irradiation, to C3H/He mice (H-2k). Bone marrow cells for injection were obtained from C57BL/6 (B6) mice (H-2b). The 9-Gy mice were reconstituted by lymphocytes of donor origin and showed GVHD, whereas 6.5-Gy mice were reconstituted by lymphocytes of recipient origin and showed mild GVHD. The liver was the organ where the reconstitution of lymphocytes occurred efficiently, and a major lymphocyte subset was intermediate (int) CD3 cells (i.e., CD3int cells) in both mice. CD3int cells had the properties of extrathymic T cells, showing the phenotype of NK1.1 + CD3int using invariant V alpha 14 chain. In 6.5-Gy mice, allogeneic cells were rejected by extrathymic T cells of recipient origin. The stored CD3int cells from the liver of 9-Gy mice evoked similar GVHD when transferred into 6.5-Gy irradiated C3H/He mice. These results suggest that CD3int cells of extrathymic origin are a major population for the induction of GVHD under immunosuppressive conditions.

T cell development in mice lacking all T cell receptor zeta family members (Zeta, eta, and FcepsilonRIgamma)

The zeta family includes zeta, eta, and FcepsilonRIgamma (Fcgamma). Dimers of the zeta family proteins function as signal transducing subunits of the T cell antigen receptor (TCR), the pre-TCR, and a subset of Fc receptors. In mice lacking zeta/eta chains, T cell development is impaired, yet low numbers of CD4+ and CD8+ T cells develop. This finding suggests either that pre-TCR and TCR complexes lacking a zeta family dimer can promote T cell maturation, or that in the absence of zeta/eta, Fcgamma serves as a subunit in TCR complexes. To elucidate the role of zeta family dimers in T cell development, we generated mice lacking expression of all of these proteins and compared their phenotype to mice lacking only zeta/eta or Fcgamma. The data reveal that surface complexes that are expressed in the absence of zeta family dimers are capable of transducing signals required for alpha/beta-T cell development. Strikingly, T cells generated in both zeta/eta-/- and zeta/eta-/--Fcgamma-/- mice exhibit a memory phenotype and elaborate interferon gamma. Finally, examination of different T cell populations reveals that zeta/eta and Fcgamma have distinct expression patterns that correlate with their thymus dependency. A possible function for the differential expression of zeta family proteins may be to impart distinctive signaling properties to TCR complexes expressed on specific T cell populations.

Mouse NK1.1+ cytotoxic T cells can be generated by IL-2 exposure from lymphocytes which express an intermediate level of T cell receptor

NK-like T cells which express the NK1.1 molecule and CD3 (or TCR) of intermediate level (CD3int or TCRint cells) were recently demonstrated to be present in various immune organs, and to have NK-like cytotoxic activity against NK target cells. In this study, we investigated whether NK1.1- T cells could express NK1.1. We found that NK1.1+ TCRint cells were much more abundant in the liver (20%) than in the spleen (2%). When hepatic and splenic mononuclear cells (MNCs) were cultured either in the absence of IL-2 or in the presence of CD3/TCR cross-linking, the original NK1.1+ TCRint cells disappeared. However, when they were cultured in the presence of a high dose of IL-2 for 4 days, a new type of NK1.1+ T cell was formed to the extent of approximately 15-20%, and the liver and spleen contained similar percentages of this new type of NK1.1+ T cells. The phenotypes of the original and the new type of NK1.1+ T cells were clearly distinct. The freshly obtained NK1.1+ TCRint cells consisted of double-negative (DN) CD4-CD8- cells and single-positive (SP) CD4+ cells, whereas the new type of NK1.1+ T cells predominantly consisted of DN CD4-CD8- cells and SP CD8+ cells and expressed a high level of CD3 (CD3high or TCRhigh cells). When NK1.1- cells or IL-2 receptor beta-chain (IL-2Rbeta)- cells were isolated from the liver and spleen, and cultured in the presence of IL-2 for 4 days, NK1.1+ T cells were generated from NK1.1- cells, but not from IL-2Rbeta- cells. Our results suggested that the NK1.1- cells, but not IL-2Rbeta- cells, contained the precursor of IL-2-stimulated NK1.1+ TCRhigh cells. When purified NK1.1- IL-2Rbeta+ TCRint cells were cultured in the presence of IL-2 for 4 days, approximately 10% of the cells became NK1.1+ TCRhigh cells. Approximately 60% of the purified NK1.1+ TCRint cells lost NK1.1 expression. The IL-2-stimulated NK1.1+ TCRhigh cells that had arisen from NK1.1- TCRint cells exerted an NK cell-like cytotoxic activity similar to that of the original NK1.1+ T cells. Thus, NK1.1- TCRint cells could express NK1.1 and exert NK-like cytotoxic activity regardless of their origin. It appears that NK1.1+ TCRhigh cells can only be induced through an IL-2-stimulation pathway but not via CD3/TCR cross-linking.

CD1.1 Expression by Mouse Antigen-Presenting Cells and Marginal Zone B Cells

Mouse CD1.1 is an MHC class I-like, non-MHC-encoded, surface glycoprotein that can be recognized by T cells, in particular NK1.1+ T cells, a subset of αβ T cells with semiinvariant TCRs that promptly releases potent cytokines such as IL-4 and IFN-γ upon stimulation. To gain insight into the function of CD1.1, a panel of nine mAbs was generated and used to biochemically characterize and monitor the surface expression of CD1.1 on different cell types. CD1.1 is a heavily glycosylated, β2-microglobulin-associated surface protein. Its recognition by a panel of 12 Vα14-positive and -negative CD1-specific αβ T cell hybridomas was blocked by two groups of mAbs that bound to adjacent clusters of epitopes, indicating that different αβ TCRs bind to the same region of CD1.1, presumably above the groove. Remarkably, CD1.1 was mainly expressed by dendritic cells, B cells, and macrophages, suggesting a function in Ag presentation to Th cells. Furthermore, the cell type that expressed the highest levels of CD1.1 was the splenic marginal zone B cell, a distinct subset of B cells that also expresses CD21 (the C3d receptor) and may be involved in natural responses to bacterial Ags. Altogether, the results support the idea that CD1.1 may function in recruiting a form of innate help from specialized cytokine producer αβ T cells to APCs, a role that might be important at the preadaptive phase of immune responses to some microbial pathogens.

Natural killer activating receptors trigger interferon gamma secretion from T cells and natural killer cells

Proliferation of human CD4+ alphabeta T cells expressing a natural killer cell activating receptor (NKAR) has been shown to be enhanced, particularly in response to low doses of antigen, if the target cells present appropriate human class I major histocompatibility complex (MHC) molecules. Here, we show that NKAR also enhance proliferation and killing of target cells by subsets of CD8+ alphabeta and CD8+ gammadelta T cells, as well as by NK cells. Strikingly, interferon gamma secretion from all of these types of lymphocytes was markedly increased by interaction of the NKAR with their MHC class I ligands, independently of enhancement of proliferation. Thus, the recognition of class I MHC molecules by NKAR on both T cells and NK cells may provide a regulatory mechanism that affects immune responses through the secretion of interferon gamma and possibly other cytokines. It represents a signal for cytokine secretion alternative and/or augmentative to that through the T cell receptor.

The transcription factor interferon regulatory factor 1 (IRF-1) is important during the maturation of natural killer 1.1+ T cell receptor-alpha/beta+ (NK1+ T) cells, natural killer cells, and intestinal intraepithelial T cells

In contrast to conventional T cells, natural killer (NK) 1.1+ T cell receptor (TCR)-alpha/beta+ (NK1+T) cells, NK cells, and intestinal intraepithelial lymphocytes (IELs) bearing CD8-alpha/alpha chains constitutively express the interleukin (IL)-2 receptor (R)beta/15Rbeta chain. Recent studies have indicated that IL-2Rbeta/15Rbeta chain is required for the development of these lymphocyte subsets, outlining the importance of IL-15. In this study, we investigated the development of these lymphocyte subsets in interferon regulatory factor 1-deficient (IRF-1-/-) mice. Surprisingly, all of these lymphocyte subsets were severely reduced in IRF-1-/- mice. Within CD8-alpha/alpha+ intestinal IEL subset, TCR-gamma/delta+ cells and TCR-alpha/beta+ cells were equally affected by IRF gene disruption. In contrast to intestinal TCR-gamma/delta+ cells, thymic TCR-gamma/delta+ cells developed normally in IRF-1-/- mice. Northern blot analysis further revealed that the induction of IL-15 messenger RNA was impaired in IRF-1-/- bone marrow cells, and the recovery of these lymphocyte subsets was observed when IRF-1-/- cells were cultured with IL-15 in vitro. These data indicate that IRF-1 regulates IL-15 gene expression, which may control the development of NK1+T cells, NK cells, and CD8-alpha/alpha+ IELs.

Age-Dependent Appearance of NK1.1+ T Cells in the Livers of β2-Microglobulin Knockout and SJL Mice

NK1.1+ T cells, a specialized set of T cells that recognize CD1, are reportedly absent in young β2-microglobulin-deficient (β2m-knockout (KO)) and SJL mice. In this study, we show that a significant number of NK1.1+ T cells exist in the livers of older β2m-KO and SJL mice, and that the number of liver NK1.1+ T cells increases as the animals age. The surface phenotypes of liver NK1.1+ T cells from β2m-KO and SJL mice were similar to NK1.1+ T cells from C57BL/6 mice, except that the bulk of these cells were CD4−CD8−. After anti-CD3 injection in vivo, the cells promptly expressed IL-4 mRNA just as NK1.1+ T cells did in normal mice. Using L cells expressing CD1, liver NK1.1+ T cells from both β2m-KO and SJL mice were stimulated to proliferate, although to a lesser degree than were such cells from C57BL/6 mice. Our studies show that some NK1.1+ T cells accumulate in the livers of older β2m-KO and SJL mice, and that they appear to have functional properties similar to “normal” NK1.1+ T cells.

A TCR alpha chain transgene induces maturation of CD4- CD8- alpha beta+ T cells from gamma delta T cell precursors

The proportion of CD4- CD8- double-negative (DN) alpha beta T cells is increased both in the thymus and in peripheral lymphoid organs of TCR alpha chain-transgenic mice. In this report we have characterized this T cell population to elucidate its relationship to alpha beta and gamma delta T cells. We show that the transgenic DN cells are phenotypically similar to gamma delta T cells but distinct from DN NK T cells. The precursors of DN cells have neither rearranged endogenous TCR alpha genes nor been negatively selected by the MIsa antigen, suggesting that they originate from a differentiation stage before the onset of TCR alpha chain rearrangements and CD4/CD8 gene expression. Neither in-frame V delta D delta J delta nor V gamma J gamma rearrangements are over-represented in this population. However, since peripheral gamma delta T cells with functional TCR beta gene rearrangements have been depleted in the transgenics, we propose that the transgenic DN population, at least partially, originates from the precursors of those cells. The present data lend support to the view that maturation signals to gamma delta lineage-committed precursors can be delivered via TCR alpha beta heterodimers.

Subsets of transgenic T cells that recognize CD1 induce or prevent murine lupus: role of cytokines

T cells with T cell receptor (TCR) transgenes that recognized CD1 on syngeneic B cells stimulated B cells to secrete immunoglobulins in vitro. The CD4+, CD8+, or CD4-CD8- T cells from the spleen of the TCR transgenic BALB/c donors induced lupus with anti-double stranded DNA antibodies, proteinuria, and immune complex glomerulonephritis in irradiated BALB/c nude mice reconstituted with nude bone marrow. Injection of purified CD4-CD8- T cells from the marrow of transgenic donors prevented the induction of lupus by the transgenic T cells. Transgenic T cells that induced lupus secreted large amounts of interferon (IFN)-gamma and little interleukin (IL)-4, and those that prevented lupus secreted large amounts of IL-4 and little IFN-gamma or IL-10.

The Ly-49 Family: Regulation of Cytotoxicity and Cytokine Production in Murine CD3+ Cells

The Ly-49 gene families are class I-recognizing receptors on murine NK cells. Most Ly-49 receptors inhibit NK cell lysis upon recognizing their target class I ligands. In this report we have examined the ability of Ly-49A and Ly-49G2 to regulate T cell functions on CD3+ cells, primarily the subset that also expresses NK-1.1 and/or DX5. The majority (&gt;50%) of T cells that express Ly-49 molecules also coexpress NK-1.1 and/or DX5, although some NK-1.1− and/or DX5−/CD3+ cells express Ly-49 molecules. Lysis of target cells by IL-2-cultured T cells expressing Ly-49A and G2 was enhanced by Abs specific for Ly-49A and G2 as well as by Abs to class I (H-2Dd α1/α2). Murine T cells also were cultured in the presence of targets that express (H-2Dd) which is inhibiting for the Ly-49A and G2 receptors. These cells were examined for a coincident increase in cytokine production (IFN-γ, TNF-α, and granulocyte-macrophage CSF). Abs to Ly-49A and G2 or their respective class I ligands blocked the negative signals mediated via the Ly-49 receptors and increased IFN-γ and granulocyte-macrophage CSF production after interaction of these T cells with H-2Dd-expressing tumor targets. Furthermore, an EL-4 T cell line expressing both Ly-49A and G2, when treated with mAb YE148 and 4D11, demonstrated reduced cytokine production and calcium mobilization. These results demonstrate for the first time that Ly-49 class I binding receptors, previously thought to be restricted to mouse NK cells, can mediate important physiological functions of T cell subsets.

A novel monoclonal antibody permitting recognition of NKT cells in various mouse strains

By immunizing mouse lymphoma cell line tMK-2U derived from intermediate TCR cells of BALB/c nude mouse, U5A2-13 monoclonal antibody (mAb, a rat IgG2a) was established. U5A2-13 antigen (Ag) was expressed on around 65% of TCRint cells in the liver of the various mouse strains including both NK1.1- and NK1.1+ mouse strains, while NK1.1 Ag was expressed only in NK1.1+ C57BL/6 mouse strain. Among CD3+ cells, 26.3% cells co-expressed U5A2-13 Ag and NK1.1+ Ag, while small proportions of the CD3+ cells were U5A2-13+NK1.1- (9.2%) or U5A2-13-NK1.1+ (4.4%). Among NK1.1+ cells, 54.9% cells co-expressed CD3 and U5A2-13 Ag, while some proportions of the cells were U5A2-13+CD3- (19.4%) or U5A2-13-CD3+ (9.8%). It was found that approximately 85% of NK1.1+CD3+ cells coexpressed U5A2-13 Ag. U5A2-13 Ag with low fluorescence intensity was also expressed on 55% of NK1.1+CD3-NK cells. U5A2-13 Ag immunoprecipitated from tMK-2U cells consisted of three proteins, which were 65 kDa, 33 kDa and 32 kDa under both reducing and non-reducing conditions and these were apparently different from NK 1.1 Ag. These results indicated that U5A2-13 mAb was able to define a similar population to NK1.1+CD3+T cells and to 55% of NK1.1+CD3-NK cells in various strains, through recognizing a different molecule from NK1.1 Ag.

Cutting Edge: Critical Role of NK1+ T Cells in IL-12-Induced Immune Responses In Vivo

CD1-dependent NK1+ T cells rapidly produce IL-4 upon stimulation through the TCR. These cells may therefore play an important role in the initiation of Th2 responses. Here, we show that NK1+ T cells constitutively express receptors for IL-12 and IFN-γ, and that IL-12 induces production of perforin in these cells. Moreover, while IL-12 induces high levels of IFN-γ and cytotoxic activity of hepatic or splenic mononuclear cells against tumor cells, this effect of IL-12 is significantly reduced in CD1-deficient mice with impaired NK1+ T cells development. These results indicate that NK1+ T cells play a critical role in IL-12-induced production of IFN-γ to initiate Th1 immune responses and as IL-12-induced cytotoxic effector cells to initiate antitumor immunity.

Resident human hepatic lymphocytes are phenotypically different from circulating lymphocytes

BACKGROUND/AIMS

Murine and human studies have documented the existence of subpopulations of lymphocytes in particular tissues that differ phenotypically and functionally from those in peripheral blood and may mature locally. Since little is known about lymphocyte subpopulations in the normal human liver, we have analysed the surface phenotypes of lymphocytes isolated from liver specimens taken from 15 donors at the time of liver transplantation, and compared these with those of peripheral blood lymphocytes.

METHODS

Hepatic lymphocytes were prepared by mechanical dissociation and enzymatic digestion of liver tissue. The cells were stained with a panel of monoclonal antibodies (CD3, CD4, CD8, CD19, CD56, gammadeltaTCR, alphabetaTCR, CD8alpha-chain, CD8alphabeta dimer), and analysed by flow cytometry. In situ characterisation of hepatic lymphocytes was by haematoxylin and eosin staining of fixed liver sections and by immunohistochemical staining for common leukocyte antigen and CD3.

RESULTS

Significant numbers of hepatic T lymphocytes were localised to the portal tracts and parenchyma of normal liver specimens. Flow cytometry revealed that the CD4/CD8 ratio (1:3.5) was consistently reversed compared with that in peripheral blood (2:1). Other lymphocyte populations identified include double positive CD3+CD4+CD8+ cells which accounted for a mean of 5.5% (range 3-11.6%) of hepatic CD3+ cells compared with 1.3% in blood (range 0.7-3.6%; p < 0.007), and double negative CD3+ CD4-8- cells (14.5%; range 2.7-29% compared with 5.0%; range 2.1-10.8%, p < 0.02). Over 15% (range 6.8-34%) of all hepatic CD3+ cells expressed a gammadeltaTCR compared to 2.7% (range 0.9-4.7%) of CD3+ peripheral blood lymphocytes (p < 0.004) and almost 50% of these coexpressed CD8. The CD8 alpha-chain was expressed without the beta-chain (CD8alpha+beta-) by 15.4% (range 4-29.1%) of hepatic T cells, but this phenotype was undetectable among peripheral blood lymphocytes (p < 0.009). Cells expressing both the T cell marker CD3 and the natural killer cell marker CD56 constituted 31.6% (range 14-54%) of all hepatic CD3+ lymphocytes but were rarely present amongst peripheral blood lymphocytes (0-6%; p < 0.0001).

CONCLUSIONS

These data are the first to describe and quantify unconventional T lymphocyte subpopulations in the normal adult human liver which may have specialised functions in regional immune responses and which may differentiate locally. These findings have important implications for our understanding of hepatic immunoregulation and the pathogenic mechanisms involved in viral and immune-mediated liver disease and allograft rejection.

IL-4 Induces Eotaxin: A Possible Mechanism of Selective Eosinophil Recruitment in Helminth Infection and Atopy

A common feature of some parasitic infections and allergic and atopic skin diseases is the involvement of Th2 lymphocytes and the dermal appearance of eosinophils (Eos). Because Th2 lymphocytes apparently do not release Eo attractants, we addressed the question of whether the Th2 cytokine IL-4 induces its production in dermal fibroblasts. We therefore stimulated fibroblasts with IL-4. HPLC investigation of supernatants revealed a single Eo chemotactic protein, which was purified to homogeneity giving a single 13-kDa band upon SDS-PAGE analyses. Peptide mapping with subsequent amino acid sequencing revealed an Eo-selective chemotaxin, which consists of a mixture of N-terminally truncated and O-glycosylated forms of the chemokine eotaxin. Other chemokines such as RANTES, MCP-3, MCP-4, or MIP-1α were not detected as Eo chemotaxins under these conditions. Using reverse transcriptase-PCR techniques, we found that IL-4 dose and time dependently induces eotaxin mRNA in dermal fibroblasts. Stimulation with IL-4 and TNF-α caused a 10- to 20-fold increase of the release of three biochemically different eotaxin forms, each consisting of a mixture of N-terminally truncated and O-glycosylated variants having the same backbone amino acid sequence but different specific activities. Our findings support the hypothesis that eosinophil recruitment seen in IL-4-mediated skin reactions, at least in part, may be due to Th2 cytokine-mediated induction of eotaxin in dermal fibroblasts.

Murine model of IgE production with a predominant Th2-response by feeding protein antigen without adjuvants

Stimulation of systemic antigen-specific IgE production plays an important role in the mediation of food allergy; however, the mechanism of IgE production against food antigens is not fully understood. The development of relevant animal models may help to elucidate the pathogenesis of food allergy. We here show that DBA/2 mice receiving a casein diet without any adjuvant produced high levels of IgE specific for casein, accompanied by predominant Th2-like responses in liver lymphocytes, mesenteric lymph node cells and spleen cells. This model of IgE production produced by feeding protein antigen as a constituent of the diet can be applied to investigate the mechanism of IgE production and to develop reagents for controlling food allergy.

Control of self-reactive cytotoxic T lymphocytes expressing gamma delta T cell receptors by natural killer inhibitory receptors

The majority of peripheral blood gamma delta T cells in human adults expresses T cell receptors (TCR) with identical V regions (V gamma 9 and V delta 2). These V gamma 9 V delta 2 T cells recognize the major histocompatibility complex (MHC) class I-deficient B cell line Daudi and broadly distributed nonpeptidic antigens present in bacteria and parasites. Here we show that unlike alpha beta or V gamma 9- gamma delta T cells, the majority of V gamma 9V delta 2 T cells harbor natural killer inhibitory receptors (KIR) (mainly CD94/NKG2A heterodimers), which are known to deliver inhibitory signals upon interaction with MHC class I molecules. Within V gamma 9V delta 2 T cells, KIR were mainly expressed by clones exhibiting a strong lytic activity against Daudi cells. In stark contrast, almost all V gamma 9V delta 2 T cell clones devoid of killing activity were KIR-, thus suggesting a coordinate acquisition of KIR and cytotoxic activity within V gamma 9V delta 2 T cells. In functional terms, KIR inhibited lysis of MHC class I-positive tumor B cell lines by V gamma 9V delta 2 cytotoxic T lymphocytes (CTL) and raised their threshold of activation by microbial antigens presented by MHC class I-positive cells. Furthermore, masking KIR or MHC class I molecules revealed a TCR-dependent recognition by V gamma 9V delta 2 CTL of ligands expressed by activated T lymphocytes, including the effector cells themselves. Taken together, these results suggest a general implication of V gamma 9V delta 2 T cells in immune response regulation and a central role of KIR in the control of self-reactive gamma delta CTL.

Expression and function of NKRP1A molecule on human monocytes and dendritic cells

In this study, we analyzed the expression and function of the lymphocyte surface lectin NKRP1A on peripheral blood monocytes (Mo) or Mo and dendritic cells (DC) derived from thymic and bone marrow precursors. De novo expression of NKRP1A and CD14 molecules was detected upon culture of CD2- CD3- CD14- CD16- CD1a- NKRP1A- immature thymic precursors for 7 days in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF). Under these culture conditions, by day 21, a fraction of cells had lost CD14 and acquired both CD80 (B7.1) and CD86 (B7.2) molecules. These cells displayed a DC-like morphology and were surface NKRP1A positive. CD34+ NKRP1A- CD14- precursors, isolated from bone marrow and cultured in the presence of GM-CSF, also expressed both NKRP1A and CD14: these antigens were newly expressed on about one third of cells which had lost the CD34 precursor marker. In addition, NKRP1A was constitutively present on resting CD14+ peripheral blood Mo. When these cells were cultured in the presence of GM-CSF, the resulting DC population retained the expression of NKRP1A and acquired CD80, while they lost the CD14 antigen. Functional analysis revealed that the engagement of NKRP1A molecule leads to a strong intracellular calcium ([Ca2+]i) increase both in resting peripheral blood Mo and in vitro-derived DC. [Ca2+]i increase was mainly due to extracellular calcium influx, as it was completely abrogated by the addition of EGTA. More importantly, the engagement of the NKRP1A molecule induced interleukin (IL)-1 beta and IL-12 production by resting Mo and DC, respectively. Altogether these data indicate that NKRP1A lectin is present at the surface of Mo and DC and may play a relevant role in the activation and function of both cell types.

Inhibition of the progression of multiple sclerosis by linomide is associated with upregulation of CD4+/CD45RA+ cells and downregulation of CD4+/CD45RO+ cells

In a recent double-blind, phase II study, conducted in our department, we showed that Linomide-treated MS patients had significantly less active lesions (in serial monthly MRI tests) and a tendency for clinical stabilization. Here we present the immunological evaluation of the patients who participated in this study and propose a novel mechanism by which Linomide downregulates autoreactivity. Peripheral blood leukocytes (PBLs), serum, and CSF samples were obtained at two to four time points over the 6 months of the trial. Flow cytometric analysis (FACS) of the CD5/CD19, CD4/CD8, CD14/CD3, CD16/CD3, CD45RA/CD4, and CD45RO/CD4 surface markers on PBLs was performed and the levels of the IL-1beta, IL-2, IL-4, IL-6, IL-10, TNF-alpha, IFN-gamma, and IL-2R were also examined. White blood counts of Linomide-treated patients were consistently elevated throughout the treatment period (P = 0.002-0.04). Cytokines levels in serum and CSF were highly fluctuating and we could not detect any clear trend as a result of Linomide treatment. FACS analysis showed that Linomide treatment significantly increased the percentage of the CD4+/CD45RA+ cells (from 35.5% at baseline to 42.3% at week 24; P = 0.02), and decreased CD4+/CD45RO+ lymphocytes (62.6% at baseline vs 53.7% at week 24, P = 0.02). Linomide also induced a transient increase in the NK-cells, the NK 1.1 cells, and the CD5 B-cells (P = 0.02). Upregulation of naive CD45RA T-lymphocytes and parallel downregulation of memory CD45RO cells seems to be one of the main mechanisms by which Linomide inhibits MS activity and may represent an alternative immunomodulating approach for the treatment of MS and autoimmunity in general.

Autoantibody production and cytokine profiles of MHC class I (beta2-microglobulin) gene deleted New Zealand black (NZB) mice

We established a colony of MHC class I deleted (knockout) NZB mice, which lack the beta2 microglobulin gene (NZB.beta2m-/-), to characterize the contribution of MHC class I to the thymic microenvironment abnormalities, autoantibody production and lupus-like disease of NZB mice. Using an extensive panel of well characterized monoclonal antibodies defining thymic epithelial and other stromal elements, we demonstrated that deletion of MHC class I molecules does not change the thymic abnormalities, including the presence of a cortical epithelial cell free region, ectopic expression of medullary epithelial antigens, and the irregular shape of the medullary epithelial network of NZB mice. Moreover, the decreased staining of MTS 33(+) cells, a marker of premature thymocyte maturation, was also seen in NZB.beta2m-/-. However, although NZB.beta2m-/- mice had approximately the same levels of IgM and IgG anti-ss and dsDNA antibodies when compared to control NZB mice, there were significant alterations in the incidence and onset of anti-erythrocyte antibody levels. NZB.beta2m-/- had a lower incidence and a delayed onset of anti-erythrocyte autoantibody production compared to that seen in NZB mice. We also compared constitutive and PHA-P-driven levels of IFN-gamma, IL-4, IL-6, and IL-12 in cells from NZB, NZB.beta-/-2, and control C57BL/6 mice. Mitogen stimulated cells showed a decreased IFN-gamma, and a marked increase in IL-6 and IL-12 in NZB and NZB.beta2m-/- mice.

Phenotypic and functional analysis of CD4+ NKRP1A+ human T lymphocytes. Direct evidence that the NKRP1A molecule is involved in transendothelial migration

In this report, we show that among human CD4+ T lymphocytes 5-20% express the C-type lectin molecule NKRP1A. This lymphocyte subset displays a slightly more limited T cell receptor V beta repertoire than the CD4+ NKRP1A- counterpart. CD4+ NKRP1A+ T lymphocytes are characterized by a high expression of beta 1 and beta 2 integrins, thus representing a T lymphocyte subset that can possibly adhere and migrate through vascular endothelium. Indeed, resting CD4+ NKRP1A+ lymphocytes, differently from the CD4+ NKRP1A- subset, migrated across endothelial cell monolayers in a Transwell chamber system. Pretreatment of CD4+ NKRP1A+ T lymphocytes with an anti-NKRP1A monoclonal antibody (mAb) strongly reduced transendothelial migration, suggesting the involvement of the NKRP1A molecule in the transmigration process. Furthermore, cells of the NKRP1A- Jurkat CD4+ T cell line stably transfected with NKRP1A cDNA migrated more rapidly and efficiently than either untransfected or mock-transfected Jurkat cells. Finally, mAb-mediated cross-linking of NKRP1A molecules in CD4+ T lymphocytes induced the up-regulation of the lymphocyte function-associated antigen 1 Mg(2+)-binding site as well as beta 1 and beta 2 integrin chains. Altogether, these findings suggest that the NKRP1A molecule is involved in transendothelial migration of resting CD4+ T lymphocytes.

Interleukin-4 and listeriosis

Experimental infection of mice with Listeria monocytogenes (L. monocytogenes) has served as an appropriate model for analyzing Th1-cell-driven immune responses. Generally, Th2 responses are absent and IL-4 is not detectable. Here, we describe experimental settings under which IL-4 is detectable in listeriosis. Our data suggest that IL-4 is rapidly produced after infection. This prompt IL-4 burst seems to stimulate chemokine responses and, therefore, may participate in the regulation of the early antilisterial host response. Soon thereafter, IL-4 production wanes. At least partially this seems to be caused by downregulation of IL-4-producing CD4+ NK1+ TCR alpha beta int lymphocytes by IL-12. In the absence of IFN-gamma responsiveness, IL-4 production is demonstrable during acquired immunity against L monocytogenes, and this elevated IL-4 production apparently contributes to disease exacerbation. In conclusion, the data are consistent with a detrimental role of IL-4 in listeriosis and active control of IL-4 synthesis by the antilisterial immune response. The rapid, but transient, IL-4 burst in listeriosis probably contributes to host defense without impairing development of the acquired T-cell response because of its shortness.

Distinct roles for signals relayed through the common cytokine receptor gamma chain and interleukin 7 receptor alpha chain in natural T cell development

The commitment, differentiation, and expansion of mainstream alpha/beta T cells during ontogeny depend on the highly controlled interplay of signals relayed by cytokines through their receptors on progenitor cells. The role of cytokines in the development of natural killer (NK)1(+) natural T cells is less clearly understood. In an approach to define the role of cytokines in the commitment, differentiation, and expansion of NK1(+) T cells, their development was studied in common cytokine receptor gamma chain (gammac) and interleukin (IL)-7 receptor alpha (IL-7Ralpha)-deficient mice. These mutations block mainstream alpha/beta T cell ontogeny at an early prethymocyte stage. Natural T cells do not develop in gammac-deficient mice; they are absent in the thymus and peripheral lymphoid organs such as the liver and the spleen. In contrast, NK1(+) T cells develop in IL-7Ralpha-deficient mice in the thymus, and they are present in the liver and in the spleen. However, the absolute number of NK1(+) T cells in the thymus of IL-7Ralpha-deficient mice is reduced to approximately 10%, compared to natural T cell number in the wild-type thymus. Additional data revealed that NK1(+) T cell ontogeny is not impaired in IL-2- or IL-4-deficient mice, suggesting that neither IL-2, IL-4, nor IL-7 are required for their development. From these data, we conclude that commitment and/or differentiation to the NK1(+) natural T cell lineage requires signal transduction through the gammac, and once committed, their expansion requires signals relayed through the IL-7Ralpha.