Differential expression of vasoactive intestinal polypeptide receptor 1 and 2 mRNA in murine intestinal T lymphocyte subtypes

Neuropeptides may exert a variety of effects on the immune cells at both systemic and mucosal immune sites. The immunoregulatory properties refer to the ability of physiological signals and pathways to influence various immune functions. Vasoactive intestinal polypeptide (VIP), a neuropeptide present in high concentration in gut, was studied for its production and receptor expression in intraepithelial and lamina propria T lymphocytes of mouse intestine. Using reverse transcription-polymerase chain reaction (RT-PCR) analysis, it was demonstrated that VIP receptor 1 (VIPR1) was constantly expressed in intraepithelial and lamina propria T lymphocytes from both small and large intestine. In contrast, VIPR2 was identified only in T cells from small intestine. Further studies on purified subpopulations of T lymphocytes indicated the existence of VIPR2 in CD8(+) T cells, but not CD4(+) and CD4CD8 double negative T cells, although all these three subpopulations displayed VIPR1. In addition, VIPR1 mRNA was detected in splenic T lymphocytes, but no signal was obtained for VIPR2 mRNA, even after stimulation of the cells with anti-CD3(epsilon)-chain mAb, phorbol 12-myristate 13-acetate (PMA) and/or VIP. The presence of VIP receptor(s) on intestinal T lymphocytes was supported by the detection of VIP on the cell surface using dual colour immunoflowcytometry. In-vitro treatment with VIP resulted in a tendency towards an increased size of the VIP immunoreactive T cell population and significantly enhanced the average immunofluorescence intensity of the surface labelling. This indicates that the receptors are partially occupied by locally produced VIP in vivo and that more peptide molecules can be bound on the lymphocytes when needed, released and accumulated in higher concentration at the action sites. We failed to detect the expression of VIP mRNA in T lymphocytes, from either intestine or spleen. These observations support that VIP may be an important immune modulator in gut acting through specific receptors on T lymphocytes. The differential mRNA expression of VIP receptor subtypes in cells with different phenotypes and in different immune compartments may suggest diverse regulatory roles of the neuropeptide in immune responses.

Both substance P and its receptor are expressed in mouse intestinal T lymphocytes

Substance P (SP), one of the most prevalent neuropeptides in gut, has been reported to have potent immune modulatory effects as a proinflammatory agent. The synthesis of SP and SP receptor expression in intraepithelial and lamina propria T lymphocytes of mouse intestine was investigated. Using RT-PCR analysis, it was demonstrated that SP receptor mRNA was exclusively expressed in intraepithelial and lamina propria T lymphocytes as well as their purified CD4+, CD8+ and CD4-CD8-CD3+ subsets. Messenger RNAs (mRNAs) for the two precursors of SP, beta and gamma-preprotachykinin-A, were also detected. These results were consistent in lymphocytes from both epithelium and lamina propria of small and large intestines, although the frequencies and/or intensities of mRNA expression varied. However, none of the findings could be repeated in splenic T lymphocytes. Activation of splenocytes with anti-CD3epsilon-chain mAb and PMA did not induce expression of SP or its receptor mRNAs. Furthermore, both cytoplasmic and surface-bound SP was demonstrated in intestinal T lymphocytes using dual color immunocytochemistry and immunoflow cytometry. In vitro treatment with SP did not significantly change the size of the SP-immunoreactive T cell population, indicating the presence of SP receptor on intestinal T lymphocytes as well as in vivo binding of endogenously released SP. Our data suggest that SP production and SP receptor expression are distinctive for mouse intestinal mucosal immunity and that SP may act as a modulator of an ongoing controlled inflammation in normal gut, by acting through its specific receptor on T lymphocytes in an autocrine and/or paracrine pattern.

Characterisation of mucosal lymphoid aggregates in ulcerative colitis: immune cell phenotype and TcR-gammadelta expression

BACKGROUND AND AIMS

A histopathological feature considered indicative of ulcerative colitis (UC) is the so-called basal lymphoid aggregates. Their relevance in the pathogenesis of UC is, however, unknown. We have performed a comprehensive analysis of the immune cells in these aggregates most likely corresponding to the lymphoid follicular hyperplasia also described in other colitides.

METHODS

Resection specimens of UC and normal colon were analysed by immunomorphometry, immunoflow cytometry, and immunoelectron microscopy, using a large panel of monoclonal antibodies.

RESULTS

(1) In all cases of UC, colonic lamina propria contained numerous basal aggregates composed of lymphocytes, follicular dendritic cells, and CD80/B7.1 positive dendritic cells. (2) CD4(+)CD28(-) alphabeta T cells and B cells were the dominant cell types in the aggregates. (3) The aggregates contained a large fraction of cells that are normally associated with the epithelium: that is, gammadelta T cells (11 (7)%) and alpha(E)beta(7)(+) cells (26 (13)%). The gammadelta T cells used Vdelta1 and were CD4(-)CD8(-). Immunoelectron microscopy analysis demonstrated TcR-gammadelta internalisation and surface downregulation, indicating that the gammadelta T cells were activated and engaged in the disease process. (4) One third of cells in the aggregates expressed the antiapoptotic protein bcl-2.

CONCLUSIONS

Basal lymphoid aggregates in UC colon are a consequence of anomalous lymphoid follicular hyperplasia, characterised by abnormal follicular architecture and unusual cell immunophenotypes. The aggregates increase in size with severity of disease, and contain large numbers of apoptosis resistant cells and activated mucosal gammadelta T cells. The latter probably colonise the aggregates as an immunoregulatory response to stressed lymphocytes or as a substitute for defective T helper cells in B cell activation. gammadelta T cells in the aggregates may be characteristic of UC.

Neuroendocrine changes in colon of mice with a disrupted IL-2 gene

Neuroendocrine peptides have a variety of physiological functions in the gastrointestinal tract. This study was carried out to investigate the impact of IL-2 deficiency on the neuroendocrine system in normal colon, and the neuroendocrine changes during colonic inflammation. Mice with homozygous disrupted IL-2 gene (IL-2-/-) spontaneously developed a bowel disease with similarities to human ulcerative colitis. Different types of colonic endocrine cells and myenteric nerves were analysed in the IL-2-/- mice using immunomorphometry. The neuropeptide contents in the colonic tissues were determined by radioimmunoassay. Age-matched healthy IL-2+/- and IL-2+/+ mice served as controls and the colonic IL-2 levels were compared between these two groups of mice by ELISA. Our data showed that less than half the amount of IL-2 was synthesized in the colon of IL-2+/- mice compared with the IL-2+/+ wild-type mice. Two major differences in the neuroendocrine colon were found between the mice with an intact and disrupted IL-2 gene. One was age-related. The frequencies of various endocrine cells and myenteric nerves increased with age in the IL-2+/+ mice. However, no such increases were seen in the mice with a disrupted IL-2 gene. Instead, the volume densities of enteroglucagon, serotonin cells and substance P (SP), vasoactive intestinal polypeptide (VIP) and total myenteric nerves were lower in the older IL-2+/- and IL-2-/- mice compared with the wild type. The other was disease-related. Polypeptide YY (PYY) cells and tissue levels of PYY, SP and VIP were significantly decreased in the IL-2-/- mice during the course of bowel inflammation compared with the healthy IL-2+/- and IL-2+/+ controls. These findings indicate that colonic neuroendocrine alterations did occur in the mice with a disrupted IL-2 gene and diminished local IL-2 level, suggesting a role of IL-2 in the regulation of the neuroendocrine system and a prevalent interaction between the immune and neuroendocrine systems in normal colon. On the other hand, there were some changes that seemed to correlate with the bowel inflammatory process. They might be associated with the impaired function in inflamed gut and contribute to the development and/or prolongation of disease.

Human uvula: characterization of resident leukocytes and local cytokine production

Upper airway infections often lead to macroscopic changes in the architecture of the uvula. Using immunomorphometric analysis, we investigated the frequency and distribution of immune cells and of cytokine-producing cells in uvular samples. Tissue macrophages, alphabeta T cells, gammadelta T cells, and B cells were, in declining order, the main cell populations. Gammadelta T cells and B cells exhibited reciprocal localization, with almost all gammadelta T cells residing in the vicinity of the epithelium, and all B cells in the glandular area. The presence of cells expressing the suppressor phenotype CD8+CD28- alphabeta T cells is suggested. Fifteen to twenty-five percent of the immune cells expressed the down-regulatory cytokine tumor growth factor beta. Most macrophages were located subepithelially, in the vicinity of the basal lamina. The composition and cytokine profile of leukocytes in the tissue suggest that the uvula may be a site, additional to the jejunal mucosa, for induction of mucosal tolerance to inhaled and ingested antigens. Concomitantly, the uvula appears to be protected from invasion of microbial pathogens by a subepithelial barrier of macrophages and gammadelta T cells.

gammadelta T cells of human early pregnancy decidua: evidence for cytotoxic potency

The immune compromise in decidua allows a semiallogeneic fetus to survive without impairing the ability of the maternal immune system to fight infections. Cytotoxic mechanisms are likely to be important in this compromise. Using RT-PCR, immunoflow cytometry and immunoelectron microscopy, the cytotoxic potential of isolated human decidual gammadelta T cells was studied. mRNA for perforin (Pf), granzymes A and B, granulysin and Fas ligand (FasL) was simultaneously expressed in decidual gammadelta T cells. Pf and FasL were not expressed on the cell surface. However, the cells constitutively synthesized Pf and stored it in cytolytic granules. Within the granules Pf mainly resided in the granule core formed by Pf-containing microvesicles. Ultrastructurally, three groups of Pf-containing granules were distinguished. They probably represent different stages of granule maturation in a process where Pf-containing microvesicles first attach to the core cortex and then are translocated across the cortex into the core. Presynthesized FasL was also stored in the core and microvesicles of the cytolytic granules. Upon degranulation by ionomycin/Ca(2+) treatment, FasL was rapidly translocated to the cell surface, demonstrating that its surface expression was not controlled by de novo biosynthesis. Thus decidual gammadelta T cells appear to perform Pf- and FasL-mediated cytotoxicity utilizing a common secretory mechanism based on cytolytic granule exocytosis. The first cytochemical visualization of lipids in the cytolytic granules is provided. These intragranular lipids probably wrap up the core and participate in packaging of the cytotoxic proteins as well as in the killing process. An ultrastructural model of a cytolytic granule is presented.

Structure of the human uvula

Eleven uvular biopsies were investigated for their morphology, the presence of mast cells and the distribution of hyaluronan and its major ligand CD44. Three microanatomical sites--surface epithelium, subepithelial area and area of glands--were examined. The oral side of the uvula was covered by a 15-20 cell thick layer of keratinized/parakeratinized surface epithelium, firmly anchored to the underlying connective tissue by connective tissue papillae. The width of the intercellular spaces in the epithelium increased toward the basal lamina, a location that exhibited intense hyaluronan and anti-CD44 staining. Most mast cells were located in the vicinity of blood vessels, at which sites there was high staining intensity of hyaluronan. Tissue mast cells could also be observed in the connective tissue septa enclosing the acini. Glands and muscle fibres became more sparse from the proximal part of the uvula to the distal end, while the amount of connective tissue increased. The localization and architecture of connective tissue elements and mast cells are consistent with the ability of the uvula to resist mechanical stresses and to develop oedema and fibrosis, respectively.

The surface epithelium of recurrent infected palatine tonsils is rich in gammadelta T cells

Using a large panel of MoAbs in quantitative morphometric analysis of immunohistochemically stained tissue sections, we compared the frequency and distribution of immune cells in palatine tonsils from patients with recurrent tonsillitis (RT) and patients with idiopathic tonsillar hypertrophy (ITH). We found that differences between the two patient groups in leucocyte populations were limited to the surface epithelium, whereas the cellular composition of interfollicular and follicular areas was similar. Most intraepithelial lymphocytes were CD8+ T cells in both groups. However, the number of intraepithelial T cells was significantly higher in RT compared with ITH. This was due to a selective increase in the number of intraepithelial CD8+ gammadelta T cells utilizing Vdelta1 and Vgamma9. In both patient groups the majority of the intraepithelial gammadelta T cells expressed Vdelta1 and Vgamma9. Subepithelially, gammadelta T cells utilizing Vgamma9 dominated over cells utilizing Vgamma8, while equal proportions expressed Vdelta1 and Vdelta2. These results suggest that cells utilizing the otherwise rare combination Vdelta1/Vgamma9 in their T cell receptors (TCR) may constitute a major gammadelta T cell population in palatine tonsils and are probably reactive to antigens specific to the tonsillar milieu. Furthermore, they indicate that preferentially this gammadelta T cell subpopulation is involved in immune reactions within the surface epithelium in RT. We speculate that gammadelta T cells are involved in clearing infectious bacteria at the tonsillar surface and in limiting inflammatory responses in the tonsils. Both local expansion and infiltration of blood cells probably contribute to the high numbers of gammadelta T cells in RT patients.

Activated human gamma delta T lymphocytes express functional lactoferrin receptors

Lactoferrin (Lf), an iron-binding protein in milk, mucosal secretions and neutrophil granules has bactericidal properties and is a source of iron for breast-fed infants. In this paper the authors show that most in vivo activated lymphocytes, i.e. freshly isolated lymphocytes from first trimester human decidua, and most in vitro activated human blood lymphocytes, express lactoferrin receptors (Lf-R), while unstimulated blood lymphocytes do not. All major lymphocyte subsets, i.e. alpha beta T cells, gamma delta T cells, CD8+ T cells, CD4+ T cells, B cells and NK cells, express Lf-R after activation. The proportion of Lf-R expressing activated gamma delta T cells is significantly larger than that of activated alpha beta T cells. Lf-R and transferrin receptors (Tr-R/CD71) show the same kinetics of appearance on activated blood lymphocytes and are, to a large extent, expressed on the same cells. However, 35% of decidual lymphocytes and 15% of activated blood lymphocytes express Lf-R only. Addition of Lf to cultures containing an optimal concentration of Tr augments the proliferative response to polyclonal T cell activators and alloantigens, suggesting that presently used standard culture conditions for in vitro activation are suboptimal in particular for gamma delta T cells. Lf-R on decidual lymphocytes contain bound Lf, which probably is produced locally. The results suggest that Lf is a growth-supporting factor, especially important in local immune responses in the mucosa.

Gamma delta T cells of human early pregnancy decidua: evidence for local proliferation, phenotypic heterogeneity, and extrathymic differentiation

The uterine mucosa in pregnancy, the decidua, allows placenta formation and survival of the fetus despite the fact that it is semiallogeneic. Decidua contains large numbers of lymphocytes, of which CD56+ cells dominate, followed by T cells expressing either alpha beta or gamma delta TCR. We have investigated the developmental relationship between the CD56- and TCR gamma delta-expressing cells in early pregnancy decidua using dual labeling immunoelectron microscopy, immunoflow cytometry, and cell fractionation. Lymphocyte subpopulations were, in addition, analyzed for expression of the cytokine receptor for IL-7 and c-kit and for mRNA expression of recombinase-activating genes 1 and 2. Four different cell populations could be distinguished: CD56+bright, CD56+dim/TCR gamma delta+low, CD56+dim/TCR gamma delta+high, and TCR gamma delta+low. Recombinase-activating genes 1 and 2 were expressed in the CD56+bright cells and to a limited degree in CD56+dim/TCR gamma delta+low cells. c-kit was preferentially expressed on the CD56+bright cells, while IL-7R was preferentially expressed on CD56+dim/TCR gamma delta+low and CD56+dim/TCR gamma delta+high cells. The CD56+dim TCR gamma delta+low and CD56+dim/TCR gamma delta+high cells displayed the characteristic morphology of large granular lymphocytes, while single positive TCR gamma delta+low cells were usually smaller and did not contain cytoplasmic granules. The gamma delta 1 gene segment was almost exclusively used in the TCR. Gamma delta T cells in mitosis were seen. We suggest that human early pregnancy decidua is a transient site for extrathymic maturation and that the progenitors of TCR gamma delta+ cells are bone marrow-derived immature cells expressing the CD56 (neural cell adhesion molecule) homing receptor.

Gamma delta T cells of human early pregnancy decidua: evidence for local proliferation, phenotypic heterogeneity, and extrathymic differentiation

The uterine mucosa in pregnancy, the decidua, allows placenta formation and survival of the fetus despite the fact that it is semiallogeneic. Decidua contains large numbers of lymphocytes, of which CD56+ cells dominate, followed by T cells expressing either alpha beta or gamma delta TCR. We have investigated the developmental relationship between the CD56- and TCR gamma delta-expressing cells in early pregnancy decidua using dual labeling immunoelectron microscopy, immunoflow cytometry, and cell fractionation. Lymphocyte subpopulations were, in addition, analyzed for expression of the cytokine receptor for IL-7 and c-kit and for mRNA expression of recombinase-activating genes 1 and 2. Four different cell populations could be distinguished: CD56+bright, CD56+dim/TCR gamma delta+low, CD56+dim/TCR gamma delta+high, and TCR gamma delta+low. Recombinase-activating genes 1 and 2 were expressed in the CD56+bright cells and to a limited degree in CD56+dim/TCR gamma delta+low cells. c-kit was preferentially expressed on the CD56+bright cells, while IL-7R was preferentially expressed on CD56+dim/TCR gamma delta+low and CD56+dim/TCR gamma delta+high cells. The CD56+dim TCR gamma delta+low and CD56+dim/TCR gamma delta+high cells displayed the characteristic morphology of large granular lymphocytes, while single positive TCR gamma delta+low cells were usually smaller and did not contain cytoplasmic granules. The gamma delta 1 gene segment was almost exclusively used in the TCR. Gamma delta T cells in mitosis were seen. We suggest that human early pregnancy decidua is a transient site for extrathymic maturation and that the progenitors of TCR gamma delta+ cells are bone marrow-derived immature cells expressing the CD56 (neural cell adhesion molecule) homing receptor.

Allergen induced cytokine profiles in type I allergic individuals before and after immunotherapy

Allergen immunotherapy (IT) involves subcutaneous injections of increasing doses of specific allergen over a period of time. It is recognised as highly effective in the treatment of patients with allergic rhinitis. However, the specific immunological mechanisms by which IT achieves its effect have not been fully elucidated. Recent studies, have shown that the clinical effects following IT of allergic individuals is concomitant with a reduced production of IL-4 by allergen specific CD4+ T-cells. The aim of the present study was to gain better knowledge about the immunological mechanisms by which IT exerts its beneficial effects. For this purpose, peripheral blood mononuclear cells (PBMC) from ten individuals receiving birch allergen or placebo in an IT-study performed in a double-blind manner, were analysed for IL-4, IFN-gamma, IL-5 and IL-10 mRNA expression at the onset of the study and during the pollen season, during treatment. Both spontaneous and in vitro allergen-induced cytokine mRNA expression was analysed using reverse transcriptase-polymerase chain reaction (RT-PCR). Spontaneous expression of IL-4 mRNA could be detected in most of the allergic patients, but not in healthy donors. The IT-treated patients showed a decrease in the spontaneous expression of IL-4 mRNA during the pollen season as compared to at the onset of the study, while in patients receiving placebo the IL-4 mRNA expression increased or remained unchanged. Similar results were obtained after in vitro stimulation with allergen. This was in contrast to the results for IFN-gamma, which was readily detected in both patient groups with no significant differences between the groups at either timepoint. IL-5 was shown to be increased during the pollen season in both groups and thereby presumably not affected by allergen IT. Taken together, these observations suggest that the cytokine profiles in circulating T lymphocytes change as a consequence of allergen IT.

Abundance of intraepithelial gamma delta T cells in hypertrophic obstructive but not in chronically infected adenoids

Using quantitative morphometric analysis of immunohistochemically stained tissue sections we compared hypertrophic obstructive adenoids (HOA, n = 10) from children without middle ear disease with chronically infected adenoids (CIA, n = 10) from children with middle ear disease. gamma delta T cell receptor (TCR)+ cells constituted the dominating T cell population in the surface epithelium of HOA, while alpha beta TCR+ cells were the dominating intraepithelial T cell population in CIA. Intraepithelially CD8+ cells dominated over CD4+ cells in both diseases. Intraepithelially B cells were not detected. The cellular composition of follicles, with B cells dominating followed by activated CD4+ alpha beta TCR+ cells, was the same in both groups. However, the number of follicles in CIA was twice as many as in HOA. In the deeper interfollicular areas granulocytes were more abundant in CIA than in HOA. The latter two findings suggest a more pronounced inflammatory response in the adenoids of patients with middle ear disease. There was no significant difference with regard to pathogenic bacterial strains colonizing the adenoid surface when comparing the two patient groups. These results suggest that in patients with HOA gamma delta TCR+ T cells help to maintain the integrity of the surface epithelium, thereby preserving its protective function. On the basis of our results we speculate that CIA have a malfunctioning defence, thereby facilitating long-standing infections deep in the adenoid. This may be the main reason for development of middle ear disease and an indication for adenoidectomy in patients with CIA.

Intraepithelial lymphocytes in human gut have lytic potential and a cytokine profile that suggest T helper 1 and cytotoxic functions

The functional properties of intraepithelial lymphocytes (IEL) in normal human jejunum, ileum, and colon were investigated. Cytokine mRNA expression in IEL and enterocytes was determined by reverse transcriptase-PCR and IFN-gamma+ IEL by immunohistochemistry. Polyclonal activators were used to study proliferation and IFN-gamma secretion of IEL, and an anti-CD3-mediated redirected cytotoxicity assay was used to determine the lytic potential of IEL. Freshly isolated IEL at all three gut levels expressed mRNA for IL-1 beta, IL-2, IL-8, IFN-gamma, and TNF-alpha. Approximately 10% of IEL produced IFN-gamma, suggesting that IEL are immunologically active in vivo, performing similar functions along the intestine. IEL could be stimulated further in vitro to express IL-10, TNF-beta, and TGF-beta 1, while no Th2-type cytokines were induced, suggesting suppressive and cytolytic functions for IEL. All three jejunal IEL subpopulations (CD4-CD8-TCR-gamma delta+, CD4+TCR-alpha beta+, CD8+TCR-alpha beta+) expressed the same four cytokines, IL-2, IL-8, IFN-gamma, and TNF-alpha, indicating that CD4+TCR-alpha beta+ IEL are Th1 cells and that TCR-gamma delta+ IEL and CD8+TCR-alpha beta+ IEL include cytotoxic effector cells. Indeed, freshly isolated jejunal IEL displayed cytolytic activity. IEL were induced to proliferation by anti-CD3/TCR complex mAbs and leukoagglutinin, but not by Con A. There was no correlation between the magnitude of the proliferative response and the amounts of secreted IFN-gamma. Enterocytes expressed IL-1 beta and IL-8, and sometimes TNF-alpha. Although jejunal enterocytes express HLA-DR and hsp60, Ag presentation by these cells may induce anergy since their cytokine profile is different from that of classical APCs.

Intraepithelial lymphocytes in human gut have lytic potential and a cytokine profile that suggest T helper 1 and cytotoxic functions

The functional properties of intraepithelial lymphocytes (IEL) in normal human jejunum, ileum, and colon were investigated. Cytokine mRNA expression in IEL and enterocytes was determined by reverse transcriptase-PCR and IFN-gamma+ IEL by immunohistochemistry. Polyclonal activators were used to study proliferation and IFN-gamma secretion of IEL, and an anti-CD3-mediated redirected cytotoxicity assay was used to determine the lytic potential of IEL. Freshly isolated IEL at all three gut levels expressed mRNA for IL-1 beta, IL-2, IL-8, IFN-gamma, and TNF-alpha. Approximately 10% of IEL produced IFN-gamma, suggesting that IEL are immunologically active in vivo, performing similar functions along the intestine. IEL could be stimulated further in vitro to express IL-10, TNF-beta, and TGF-beta 1, while no Th2-type cytokines were induced, suggesting suppressive and cytolytic functions for IEL. All three jejunal IEL subpopulations (CD4-CD8-TCR-gamma delta+, CD4+TCR-alpha beta+, CD8+TCR-alpha beta+) expressed the same four cytokines, IL-2, IL-8, IFN-gamma, and TNF-alpha, indicating that CD4+TCR-alpha beta+ IEL are Th1 cells and that TCR-gamma delta+ IEL and CD8+TCR-alpha beta+ IEL include cytotoxic effector cells. Indeed, freshly isolated jejunal IEL displayed cytolytic activity. IEL were induced to proliferation by anti-CD3/TCR complex mAbs and leukoagglutinin, but not by Con A. There was no correlation between the magnitude of the proliferative response and the amounts of secreted IFN-gamma. Enterocytes expressed IL-1 beta and IL-8, and sometimes TNF-alpha. Although jejunal enterocytes express HLA-DR and hsp60, Ag presentation by these cells may induce anergy since their cytokine profile is different from that of classical APCs.

Intra-epithelial lymphocytes. Evidence for regional specialization and extrathymic T cell maturation in the human gut epithelium

The human gut epithelium is a unique immunological compartment, containing substantial amounts of intra-epithelial lymphocytes (IEL) with unknown functions. In this study we show that distinct and unusual subpopulations of IEL are present at different levels of human intestine. IEL phenotypes in normal jejunum, ileum and colon were compared using immunoflow cytometry and immunohistochemistry. The expression of mRNA for recombination-activating gene-1 (RAG-1) in IEL from all three levels was compared using reverse-transcription polymerase chain reaction, and the morphology of IEL in situ was determined using immunoelectron microscopy. Surface marker profiles of isolated intestinal epithelial cells at all three levels were also investigated. On average the proportion of TCR gamma delta IEL was comparable in jejunum than ileum and colon and varied in phenotype with gut level. CD4-CD8-TCR alpha beta IEL dominated in colon but were absent in jejunum. CD8+ TCR alpha beta IEL were present at all levels but only in jejunum did they constitute the majority of all IEL. CD4+ TCR alpha beta IEL were present in similar frequencies at all levels of the gut. In general, the majority of IEL had an activated phenotype (CD45RO+, alpha E beta 7+). Furthermore, IEL exhibited phenotypes which are rare in peripheral blood. The thymocyte markers CD1a and CD1c as well as the NK cell marker CD56 were expressed on a fraction of TCR alpha beta and TCR gamma delta IEL. A small population of 'null' cells (CD45+ TCR/CD#-CD20-CD14-CD15- cells) was also present at equal proportions along the gut. Jejunal but not colonic IEL expressed RAG-1 mRNA suggesting that extrathymic T cell maturation occurs in the epithelium of small intestine. RAG-1 was expressed in CD2+TCR/CD3- and CD3+/TCR-IEL. Ultrastructurally, IEL often formed small clusters and intimate contacts with epithelial cells, suggesting cell cooperation within the epithelium. Some IEL had pseudopodium-like extensions penetrating the epithelial basement membrane suggesting transmigration. Epithelial cells in small intestine but not colon expressed heat shock protein 60 and HLA-DR. CD1a, CD1b and CD1c were not expressed on intestinal epithelial cells at any level. The distinct surface marker profiles of IEL and epithelial cells along small and large intestine suggest functional regional specialization and are compatible with the hypothesis that TCR alpha beta IEL participate in immune reactions to lumenal antigens while TCR gamma delta IEL perform surveillance of the epithelium.

Cytokine profiles for human V gamma 9+ T cells stimulated by Plasmodium falciparum

V gamma 9+ T cells from malaria non-exposed donors make proliferative responses to Plasmodium falciparum on in vitro stimulation. V gamma 9+ cells are strongly activated by components of the schizont stage of the parasite and by antigens released into the culture upon schizogony, while CD4+V gamma 9- cells are stimulated by the earlier stages of the parasite. Using reverse transcriptase-polymerase chain reaction (RT-PCR) we determined mRNA expression for 14 cytokines in highly purified V gamma 9+ cells enriched by positive selection after in vitro stimulation with P. falciparum schizont antigens. Interferon-gamma (IFN-gamma) and Tumor Necrosis Factor-alpha (TNF-alpha) were detected in all samples tested. The majority of samples also expressed TNF-beta, transforming growth factor-beta (TGF-beta) and Interleukin-8 (IL-8). Only occasional samples expressed IL-2, IL-5 and IL-10. Using the ELISPOT assay we found that a large fraction of the reactive V gamma 9+ cells produced IFN-gamma and that gamma delta T cells are the major producers of IFN-gamma in cultures stimulated with schizont antigens. The majority of V gamma 9+ cells in these cultures also express the membrane-bound form of TNF-alpha. Expression of these cytokines speaks for a cytolytic and/or inflammatory role of gamma delta cells in the response to malaria in non-exposed individuals.

Cytokine profile and ultrastructure of intraepithelial gamma delta T cells in chronically inflamed human gingiva suggest a cytotoxic effector function

We have shown that gamma delta T cells in human gingiva have an intraepithelial location and, that in the chronic inflammatory disease periodontitis, the expression of CD45RO and CD8 or CD4 is induced on gamma delta T cells. To study the role of gamma delta T cells in local antibacterial responses, we determined the cytokine profiles of isolated human gingival cells. Different T cell subpopulations, isolated by positive selection with mAb-coated magnetic beads and macrophages, as well as epithelial cells, were analyzed for expression of mRNA for 15 cytokines by reverse transcriptase-PCR. The ultrastructure of gingival gamma delta T cells was also studied. The gamma delta T cells expressed mRNA for IFN-gamma, TNF-alpha, TGF-beta 1, and IL-6. Expression of IFN-gamma was a consequence of inflammation. CD4+ gamma delta T cells expressed IFN-gamma only, whereas CD8+ gamma delta T cells expressed all four cytokines. CD8+ cells expressing IFN-gamma, TNF-alpha, and IL-6 in combination suggest a cytotoxic effector function. Gingival gamma delta T cells contained cytoplasmic electron-dense membrane-bound granules and multivesicular bodies that are ultrastructural characteristics of cytotoxic cells. Epithelial cells from inflamed gingiva expressed HLA-DR, CD1a, CD1c, and heat shock protein 60 on the cell surface. They also expressed mRNA for IL-1 beta, IL-6, IL-8, TNF-alpha, and TGF-beta 1. Thus, epithelial cells may function as accessory cells in immune activation and, at the same time, be target cells for CD8+ gamma delta T cells reactive with CD1 Ag or heat shock protein. These results suggest that gamma delta T cells constitute a first line of defense in gingiva, preventing entrance of pathogens by cytotoxicity against infected and stressed epithelial cells, and by control of epithelial cell growth through secretion of regulatory cytokines.

Cytokine profile and ultrastructure of intraepithelial gamma delta T cells in chronically inflamed human gingiva suggest a cytotoxic effector function

We have shown that gamma delta T cells in human gingiva have an intraepithelial location and, that in the chronic inflammatory disease periodontitis, the expression of CD45RO and CD8 or CD4 is induced on gamma delta T cells. To study the role of gamma delta T cells in local antibacterial responses, we determined the cytokine profiles of isolated human gingival cells. Different T cell subpopulations, isolated by positive selection with mAb-coated magnetic beads and macrophages, as well as epithelial cells, were analyzed for expression of mRNA for 15 cytokines by reverse transcriptase-PCR. The ultrastructure of gingival gamma delta T cells was also studied. The gamma delta T cells expressed mRNA for IFN-gamma, TNF-alpha, TGF-beta 1, and IL-6. Expression of IFN-gamma was a consequence of inflammation. CD4+ gamma delta T cells expressed IFN-gamma only, whereas CD8+ gamma delta T cells expressed all four cytokines. CD8+ cells expressing IFN-gamma, TNF-alpha, and IL-6 in combination suggest a cytotoxic effector function. Gingival gamma delta T cells contained cytoplasmic electron-dense membrane-bound granules and multivesicular bodies that are ultrastructural characteristics of cytotoxic cells. Epithelial cells from inflamed gingiva expressed HLA-DR, CD1a, CD1c, and heat shock protein 60 on the cell surface. They also expressed mRNA for IL-1 beta, IL-6, IL-8, TNF-alpha, and TGF-beta 1. Thus, epithelial cells may function as accessory cells in immune activation and, at the same time, be target cells for CD8+ gamma delta T cells reactive with CD1 Ag or heat shock protein. These results suggest that gamma delta T cells constitute a first line of defense in gingiva, preventing entrance of pathogens by cytotoxicity against infected and stressed epithelial cells, and by control of epithelial cell growth through secretion of regulatory cytokines.

High expression of V gamma 8 is a shared feature of human gamma delta T cells in the epithelium of the gut and in the inflamed synovial tissue

We have analyzed the V-gene usage in gamma delta T cells of the human gut and joint by using a new mAb (B18) specific for V gamma 8 of human TCR-gamma delta+ T cells. The B18+ population constituted a minor subset of the gamma delta T cells in peripheral blood (PB) of healthy persons (6 +/- 5%) and only 1 of 35 gamma delta T cell clones analyzed was positive. In contrast, the B18+ subset was a dominant gamma delta T cell population among intraepithelial lymphocytes (IEL) derived from the human intestine (74 +/- 29, p < 0.002), and two of three IEL clones from patients with coeliac disease were B18+. Interestingly, a higher proportion of B18+ gamma delta T cells was found in the synovial fluid of patients with rheumatoid arthritis (RA) (21 +/- 18%, 0.02 < p < 0.05) compared with normal PB. Furthermore, the B18+ subset was more frequent among IL-2-expanded gamma delta T cells (42 +/- 20%) derived from synovial tissue than among IL-2-expanded cells derived from synovial fluid (p < 0.002) and PB from RA patients (p < 0.02) as well as normal PB (p < 0.002). The V-gene usage of 13 gamma delta T cell clones from the synovial fluid of arthritic patients was analyzed. All B18+ clones (n = 7) expressed mRNA for V gamma 8 together with mRNA for V delta 1 (n = 5) or mRNA for V delta 3 (n = 2). None of the B18- clones expressed V gamma 8 (n = 6). We conclude that the gamma delta T cell that expresses V gamma 8, together with mainly V delta 1, is a major gamma delta T cell subset among the IEL of the gut and a highly frequent subset in the synovial tissue of patients with RA. This subset may correspond to the mouse V gamma 7+ IEL, which has a high degree of amino acid sequence homology with the human V gamma 8 protein.

High expression of V gamma 8 is a shared feature of human gamma delta T cells in the epithelium of the gut and in the inflamed synovial tissue

We have analyzed the V-gene usage in gamma delta T cells of the human gut and joint by using a new mAb (B18) specific for V gamma 8 of human TCR-gamma delta+ T cells. The B18+ population constituted a minor subset of the gamma delta T cells in peripheral blood (PB) of healthy persons (6 +/- 5%) and only 1 of 35 gamma delta T cell clones analyzed was positive. In contrast, the B18+ subset was a dominant gamma delta T cell population among intraepithelial lymphocytes (IEL) derived from the human intestine (74 +/- 29, p < 0.002), and two of three IEL clones from patients with coeliac disease were B18+. Interestingly, a higher proportion of B18+ gamma delta T cells was found in the synovial fluid of patients with rheumatoid arthritis (RA) (21 +/- 18%, 0.02 < p < 0.05) compared with normal PB. Furthermore, the B18+ subset was more frequent among IL-2-expanded gamma delta T cells (42 +/- 20%) derived from synovial tissue than among IL-2-expanded cells derived from synovial fluid (p < 0.002) and PB from RA patients (p < 0.02) as well as normal PB (p < 0.002). The V-gene usage of 13 gamma delta T cell clones from the synovial fluid of arthritic patients was analyzed. All B18+ clones (n = 7) expressed mRNA for V gamma 8 together with mRNA for V delta 1 (n = 5) or mRNA for V delta 3 (n = 2). None of the B18- clones expressed V gamma 8 (n = 6). We conclude that the gamma delta T cell that expresses V gamma 8, together with mainly V delta 1, is a major gamma delta T cell subset among the IEL of the gut and a highly frequent subset in the synovial tissue of patients with RA. This subset may correspond to the mouse V gamma 7+ IEL, which has a high degree of amino acid sequence homology with the human V gamma 8 protein.

Immunomorphologic studies of human decidua-associated lymphoid cells in normal early pregnancy

Human decidual lymphocytes from early, normal pregnancy were characterized in situ with respect to ultrastructure and distribution of subsets. The ultrastructure of isolated decidual gamma delta T cells was also studied. CD45+ cells comprised 11 +/- 2% of all decidual cells. The majority were localized in large lymphoid cell clusters (LCC), near endometrial glands, or as intraepithelial lymphocytes (IEL) in glandular epithelium. The major cell populations in LCC were CD56+TCR-gamma delta+ cells, CD56+ cells, TCR-alpha beta+CD4+ cells, and TCR-alpha beta+CD8+ cells. All expressed activation markers (CD45RO, Kp43, and/or HML-1) and MHC class II Ag (HLA-DR, HLA-DP, and/or HLA-DQ). No B cells were found. Almost all IEL were activated TCR-gamma delta+ cells (CD56+ and CD56-). The glandular epithelial cells expressed heat shock protein 60 at the basolateral side facing the TCR-gamma delta+ IEL. Decidual lymphocytes displayed cytoplasmic processes, microvilli, characteristic cytoplasmic granules, and had intimate contact with neighboring cells. Lymphocytes in the outer rim of LCC and the stroma showed signs of cellular movement. Two main morphotypes of gamma delta T cells could be distinguished. One had single microvilli, membrane-bound granules, and nuclear inclusions. The other had many microvilli, nonmembrane-bound granules and cytoplasmic multivesicular bodies. Our data suggest that LCC are centers of immune reactivity where T and NK cells become activated. The activated cells may guard against infections and undue trophoblast invasion and/or be involved in modulating the local maternal immune system toward unresponsiveness against the semiallogeneic fetus.

Immunomorphologic studies of human decidua-associated lymphoid cells in normal early pregnancy

Human decidual lymphocytes from early, normal pregnancy were characterized in situ with respect to ultrastructure and distribution of subsets. The ultrastructure of isolated decidual gamma delta T cells was also studied. CD45+ cells comprised 11 +/- 2% of all decidual cells. The majority were localized in large lymphoid cell clusters (LCC), near endometrial glands, or as intraepithelial lymphocytes (IEL) in glandular epithelium. The major cell populations in LCC were CD56+TCR-gamma delta+ cells, CD56+ cells, TCR-alpha beta+CD4+ cells, and TCR-alpha beta+CD8+ cells. All expressed activation markers (CD45RO, Kp43, and/or HML-1) and MHC class II Ag (HLA-DR, HLA-DP, and/or HLA-DQ). No B cells were found. Almost all IEL were activated TCR-gamma delta+ cells (CD56+ and CD56-). The glandular epithelial cells expressed heat shock protein 60 at the basolateral side facing the TCR-gamma delta+ IEL. Decidual lymphocytes displayed cytoplasmic processes, microvilli, characteristic cytoplasmic granules, and had intimate contact with neighboring cells. Lymphocytes in the outer rim of LCC and the stroma showed signs of cellular movement. Two main morphotypes of gamma delta T cells could be distinguished. One had single microvilli, membrane-bound granules, and nuclear inclusions. The other had many microvilli, nonmembrane-bound granules and cytoplasmic multivesicular bodies. Our data suggest that LCC are centers of immune reactivity where T and NK cells become activated. The activated cells may guard against infections and undue trophoblast invasion and/or be involved in modulating the local maternal immune system toward unresponsiveness against the semiallogeneic fetus.

T-cell receptor gamma delta-expressing intraepithelial lymphocytes are present in normal and chronically inflamed human gingiva

The phenotypic profile of leucocytes in diseased and normal gingival tissue was studied in situ and in isolated gingival mononuclear cell (GMC) preparations. T-cell receptor (TcR)gamma delta + cells showed preferential localization to epithelium, both in normal and inflamed gingiva, and were present in crevicular as well as oral epithelium. In normal gingiva > or = 30% of the isolated leucocytes expressed TcR gamma delta, of which the majority were CD4- CD8-, and expressed CD45RA. The proportion of TcR gamma delta + cells in GMC from periodontitis tissue varied between 2 and 32%. In contrast to normal gingiva the majority of TcR gamma delta + cells in diseased tissue were CD8+ and expressed CD45RO. Thus expression of the CD8 antigen on gingival TcR gamma delta + cells is probably a consequence of immune activation. Numerous Langerhans' cells and keratinocytes expressing the major histocompatibility complex (MHC) class I-like antigen, CD1, were present within normal and inflamed gingival epithelium in close proximity to the TcR gamma delta + cells. Most CD1a+ cells were scattered within oral epithelium. CD1c+ cells were localized close to the basal layer of crevicular epithelium. No CD1b+ cells were found. TcR alpha beta + cells, CD4+ and B cells were restricted to lamina propria of periodontitis lesions. The presence of intraepithelial TcR gamma delta + cells in normal gingiva suggests that they constitute the 'first line of defence' against the potentially harmful microflora in the oral cavity. Induction of CD8 and CD45RO antigens on TcR gamma delta + cells in periodontitis tissue indicate that they play a significant role in the disease. CD1 molecules on Langerhans' cells and keratinocytes may be the restriction elements for the CD8+ TcR gamma delta + cells.

Human decidual leukocytes from early pregnancy contain high numbers of gamma delta+ cells and show selective down-regulation of alloreactivity

The mononuclear lymphoid cell population in human pregnant uterus mucosa, decidua, from early normal pregnancies was studied phenotypically and functionally. The phenotype was determined in situ by immunohistochemistry, and in isolated decidual mononuclear cell preparations by immunofluorescence and flow cytometry. A mild isolation procedure of gentle mechanical disruption followed by density gradient centrifugation was used. Leukocytes comprised a large part of the decidual tissue. They were present in aggregates mainly situated adjacent to the glandular epithelium. In addition, individual leukocytes were present intraepithelially, as well as scattered between the stromal cells and around vessels and lacunes. Four lymphocyte populations of approximately the same size were identified: TCR gamma delta+/CD56+ cells, TCR gamma delta+/CD56- cells, TCR gamma delta-/CD56+ cells, and TCR alpha beta+/CD8+ cells. TCR gamma delta- expressing cells comprised about 60% of the T cells. They were CD4-/CD8-, and about half of the TCR gamma delta+ cells expressed the memory/activation marker CD45RO. The Kp 43 Ag, earlier described on activated CD56+ and TCR gamma delta+ cells in peripheral blood, was essentially only expressed on the TCR gamma delta-/CD56+ cell population in decidua. At least 50% of the TCR alpha beta+ cells were CD8+. The function(s) of either one of these populations might be to prevent immunologic reactions against the fetus, to protect the uterus from unwanted extensive invasion of trophoblasts, or to protect the uteroplacental unit from infection. Decidual T cells did not respond to stimulation by alloantigens or mitogenic anti-CD3 mAb but responded to the same extent as PBMC to mitogenic lectins. The surface density of the TCR/CD3 complex was low on freshly isolated decidual lymphocytes, but could be up-regulated upon stimulation with PMA/Ionomycin. Local selective down-regulation of surface expression of the TCR/CD3 complex and of activation involving this complex might be one of the mechanisms by which a maternal immunologic reaction against the semiallogeneic fetus is prevented.

Human decidual leukocytes from early pregnancy contain high numbers of gamma delta+ cells and show selective down-regulation of alloreactivity

The mononuclear lymphoid cell population in human pregnant uterus mucosa, decidua, from early normal pregnancies was studied phenotypically and functionally. The phenotype was determined in situ by immunohistochemistry, and in isolated decidual mononuclear cell preparations by immunofluorescence and flow cytometry. A mild isolation procedure of gentle mechanical disruption followed by density gradient centrifugation was used. Leukocytes comprised a large part of the decidual tissue. They were present in aggregates mainly situated adjacent to the glandular epithelium. In addition, individual leukocytes were present intraepithelially, as well as scattered between the stromal cells and around vessels and lacunes. Four lymphocyte populations of approximately the same size were identified: TCR gamma delta+/CD56+ cells, TCR gamma delta+/CD56- cells, TCR gamma delta-/CD56+ cells, and TCR alpha beta+/CD8+ cells. TCR gamma delta- expressing cells comprised about 60% of the T cells. They were CD4-/CD8-, and about half of the TCR gamma delta+ cells expressed the memory/activation marker CD45RO. The Kp 43 Ag, earlier described on activated CD56+ and TCR gamma delta+ cells in peripheral blood, was essentially only expressed on the TCR gamma delta-/CD56+ cell population in decidua. At least 50% of the TCR alpha beta+ cells were CD8+. The function(s) of either one of these populations might be to prevent immunologic reactions against the fetus, to protect the uterus from unwanted extensive invasion of trophoblasts, or to protect the uteroplacental unit from infection. Decidual T cells did not respond to stimulation by alloantigens or mitogenic anti-CD3 mAb but responded to the same extent as PBMC to mitogenic lectins. The surface density of the TCR/CD3 complex was low on freshly isolated decidual lymphocytes, but could be up-regulated upon stimulation with PMA/Ionomycin. Local selective down-regulation of surface expression of the TCR/CD3 complex and of activation involving this complex might be one of the mechanisms by which a maternal immunologic reaction against the semiallogeneic fetus is prevented.

Isolation of functionally active intraepithelial lymphocytes and enterocytes from human small and large intestine

A mild purification method has been developed for the isolation of human intraepithelial lymphocytes (IEL) and enterocytes from the same individual. The isolation procedure includes mechanical disruption of the mucosal layer, treatment with reducing agent and sedimentation followed by Percoll gradient centrifugation. Finally, epithelial cells are removed from the IEL fraction using magnetic beads coated with the anti-epithelial antigen monoclonal antibody (mAb) BerEP4. Leucocytes are removed from the enterocyte fraction using magnetic beads coated with mAbs directed against common leucocyte antigen (CD45). Using this procedure IEL and enterocytes have been isolated from apparently normal jejunal, ileal and colonic tissue specimens. Recoveries of IEL were 7 x 10(5), 4 x 10(5) and 1 x 10(5)/cm2 mucosa from jejunum, ileum and colon respectively. 1-2 x 10(6) enterocytes/cm2 mucosa were recovered from small intestine while the corresponding value for colonic biopsies was approximately 2 x 10(5) enterocytes/cm2. The IEL fraction was pure as judged by the low percentages of B cells, macrophages and BerEP4 positive cells (less than 4%) present in the purified fraction. The enterocyte fraction contained less than 2% CD45+ cells. The two cell fractions were viable and expanded in vitro. Enterocytes expanded spontaneously while IEL required initial stimulation with mitogens. The isolation procedure described here will make it possible to study the function of human IEL, interactions between IEL and enterocytes and the role of both cell types in local immunity.

Specificity and affinity of monoclonal antibodies against carcinoembryonic antigen

The binding specificities of 52 well-characterized monoclonal antibodies (Mabs) against carcinoembryonic antigen (CEA) from 12 different research groups were studied by immunohistochemistry and immuno flow cytometry. In addition, the binding constant for the interaction between Mab and CEA was determined by a solution-phase assay. Cryostat sections of colon carcinoma and normal colon, stomach, liver, pancreas, and spleen were studied by immunohistochemistry. Peripheral blood granulocytes, monocytes, and lymphocytes were assayed by immuno flow cytometry. The Mabs used here have previously been classified into five essentially nonoverlapping epitope groups (GOLD 1-5) (Cancer Res., 49: 4852-4858, 1989). Most Mabs cross-reacted with different normal tissues, ranging from highly cross-reactive Mabs (positive reaction with 8 of 9 discriminating tissues) to relatively specific Mabs (positive reaction with 1 of 9 discriminating tissues). Five Mabs (10%) were specific, reacting only with colon carcinoma, normal colon mucosa, and normal gastric foveola. There was a correlation between epitope group and binding specificity. Mabs with a high degree of CEA specificity almost exclusively belonged to epitope groups 1, 2, and 3, while highly cross-reactive Mabs belonged to epitope groups 4 and 5. There was no correlation between antibody specificity and affinity for CEA. Specific Mabs with high as well as low affinity were found.

Human milk contains proteins that stimulate and suppress T lymphocyte proliferation

The modulatory effect of human milk proteins from colostrum and late milk on the proliferative response of human T lymphocytes activated by mitogens (OKT3 and leucoagglutinin from Phaseolus vulgaris) and alloantigens was studied. High concentrations (10-100 micrograms/ml) of crude colostral milk proteins had an inhibitory effect on T cell growth while low concentrations (0.1-1 microgram/ml) enhanced T cells growth. In contrast, proteins from late milk did not inhibit T lymphocyte proliferation while the enhancing effect was retained. Colostrum was fractionated by ammonium sulphate precipitation and gel filtration on sepharose 6B. The inhibitory activity was recovered in a protein fraction containing lactoferrin as its major component. Lactoferrin was, however, not responsible for the observed inhibition. On the contrary, lactoferrin in most cases augmented the proliferative response induced by polyclonal activators. The inhibitory activity was found to bind concanavalin A-sepharose suggesting an association with glycoprotein. Inhibitory fractions contained glycoproteins of the following molecular sizes 26, 74/76 (doublet), 84, 145 and 160 kD under reducing conditions. The inhibitory effect appeared to be lymphocyte specific since the active fraction did not inhibit the growth of tissue culture cells (HeLa cells and human fibroblasts) or bacteria. Furthermore, the fraction was not toxic for lymphocytes. The inhibitory colostrum factor may prevent the newborn from overreacting immunologically against the environmental antigens encountered at birth.

Monoclonal antibodies against leucoagglutinin-reactive human T-lymphocyte surface components. I. Characterization of cellular binding sites

The binding specificities of three biologically active anti-lymphocyte monoclonal antibodies (MoAb) (K46M, K3G, and 3-19-2) produced against human T-cell surface components reactive with the mitogenic lectin leucoagglutinin from Phaseolus vulgaris (La) were analysed. K46M is a strong T-cell mitogen, while K3G and 3-19-2 inhibited cell-mediated cytotoxicity. Resting peripheral blood lymphocytes (PBL) contained 4-16% K46M+ cells, 8-35% K3G+ cells, and less than 0.3-4% 3-19-2+ cells. After stimulation with T-cell mitogens the proportion of K46M+ and 3-19-2+ cells increased markedly (mean 59 and 30% positive cells, respectively), while the increase in K3G+ cells was less prominent (38%). K46M-reactive structures were expressed on mature T cells and probably also on B cells. K3G reacted with B and T cells while 3-19-2 showed a broader specificity reacting also with erythrocytes. All three MoAb reacted with lipid extracts of resting and activated PBL as well as with purified neutral glycolipids of lymphoid origin. In addition 3-19-2 reacted with lipid extracts of erythrocytes. K46M immuno-precipitated four surface peptides from lectin-stimulated PBL. Their apparent molecular weights were 53,000, 42,000, and 16,000 (doublet). The 53,000 and 42,000 MW peptides were identified as the alpha and beta chains of the T-cell antigen receptor. The identity of the 16,000 MW peptides is presently unknown. K3G and 3-19-2 did not specifically precipitate any lymphocyte surface peptide.

Monoclonal antibodies against leucoagglutinin-reactive human T-lymphocyte surface components. II. Studies on the mechanism of K46M-induced activation and determination of the frequency of responding cells

A monoclonal antibody, K46M (IgM kappa), obtained after immunization with leucoagglutinin (La)-reactive T-cell surface components, stimulated human lymphocytes to proliferate. It induced maximal proliferation at greater than 20 micrograms IgM/ml after 3-4 days of culture. Cells stimulated by K46M produced interleukin 2 (IL-2) and gamma interferon (IFN-gamma) and expressed receptors for IL-2 and transferrin. The majority of the activated cells were phenotypically T cells as defined by monoclonal antibodies against CD3 and CD2, and an increase in the K46M-positive cells was also observed during the activation period. K46M-activated cells display major histocompatibility complex (MHC)-unrestricted cytotoxicity against several cultured target cells. The frequencies of the cytotoxic and of the proliferative precursor cells were determined using a limiting dilution assay. K46M seems to activate a larger fraction of cytotoxic precursor cells against Molt 4 than against K562, but the statistical significance of these observations requires further exploration. Both K46M or La activated 40% of PBL to proliferate, whereas 70% of PBL were induced by OKT3. However, the frequency of K46M-activated cells was 40% only when the lymphocytes were plated at low cell densities, i.e. less than 0.5 cells per well. At higher densities an inhibition of proliferation was seen that resulted in a biphasic response curve, indicating that the activation of PBL by K46M was not a single hit event. This was not found with either La or OKT3. Whether K46M, in contrast to OKT3 and La, activates a subpopulation with suppressor activity remains to be established.

Characterization of human CD4+ T-cell clones that secrete helper factor(s) for B-cell proliferation and maturation

Human peripheral blood lymphocytes (PBL) were activated with K46M, a m mitogenic monoclonal antibody against La-reactive T lymphocyte surface structures. The cultures were expanded in the presence of interleukin 2 (IL-2). After 1 month of culture, the activated T cells were cloned by limiting dilution at 0.5 cells/well. Five clones with the CD3+CD4+ phenotype and one clone with the CD3+CD8+ phenotype were obtained. The CD3+CD8+ clone (K99) displayed a strong major histocompatibility complex (MHC)-unrestricted cytolytic activity against MOLT-4 and a weaker reactivity against the bladder tumour cell lines T24 and RT4. The natural killer (NK)-susceptible K562 cells were not lysed. Two of the CD3+CD4+ clones (K91 and K914) showed a helper activity in pokeweed mitogen (PWM)-induced IgG production by B cells. These cells differed in the expression of CD45R and CDw29 antigens, as defined by the monoclonal antibodies 2H4 or D10D11 and 4B4. When stimulated with PWM for 48 or 72 h, clone K91 and an additional CD4-positive clone (K913) secreted a factor into the supernatants which helped B cells to produce IgG. The K913 supernatant also induced some IgM production. The supernatant obtained after similar stimulation of K914 cells was inactive. None of these supernatants induced B cells to proliferate when tested together with phorbol myristate acetate (PMA). However, when K91 and K914 cells were activated with phytohaemagglutinin (PHA) for 48 or 72 h, the supernatant from K91 was strongly helpful in B-cell proliferation, whereas the supernatant from K914 cultures was only moderately active. In conclusion, we have established human T helper clones that release different factors supporting either B-cell proliferation or maturation when stimulated with PWM or PHA.

Studies on the role of lymphocyte function-associated antigen 1 (LFA-1) in T cell activation

The effect of polyclonal (anti alpha and beta chain) and monoclonal (anti alpha-chain) antibodies against lymphocyte function-associated antigen 1 (LFA-1) on T cell activation was studied. When added at the beginning of activation but not after 24 h or later the antibodies as well as the F(ab')2 or Fab fragments of polyclonal antibodies inhibited concanavalin A (Con A)-induced proliferation, interleukin 2 (IL-2) production, and the expression of receptors for IL-2 and transferrin. The inhibitory effect reached a maximum at the same time as optimal proliferation (72 h). Inhibition of proliferation lasted for 5 days or longer, although IL-2 production was only inhibited during the first 48 h of culture. Receptors for IL-2 and transferrin were re-expressed to the original level after 3 days of activation. Addition of external IL-2 at the beginning of the anti-LFA-1 containing culture prevented the inhibition of IL-2 receptor expression, while inhibition of transferrin receptor expression was unaffected, supporting the conclusion that the expression of these two receptors is regulated by partially independent signals. The polyclonal and monoclonal anti-LFA-1 antibodies also inhibited phorbol ester (PMA)-dependent OKT3 activation of highly purified T cells. The results suggest that the LFA-1 antibodies block an early step in the reactions necessary for IL-2 production, and that the LFA-1 molecule participates not only in T cell-accessory cell interaction but also in T-T interaction during the early phases of the activation process.

T lymphocytes displaying major histocompatibility complex-unrestricted cytotoxicity after activation by K46M, a mitogenic monoclonal antibody against leucoagglutinin-reactive human T lymphocyte surface components

Activation of human peripheral blood lymphocytes (PBL) with the mitogenic monoclonal antibody (MoAb) K46M, which recognizes 1-5% of PBL, resulted in the expansion of cells with cytolytic activity. Thus, after culture of the activated lymphocytes in medium containing interleukin 2 (IL-2), they lysed a variety of cultured cell lines. The majority of the activated lymphocytes reacted with MoAb to CD8, CD3, and to the T cell antigen receptor heterodimer (Ti) but not with antibodies to antigens expressed on natural killer (NK) cells. The cytotoxicity was not inhibited by MoAb to CD3 or Ti. However, the killing of K562, but not of other cell lines, was enhanced by three to four times in the presence of anti-Ti antibodies. Anti-CD3 or other control antibodies had no effect. Cold target inhibition experiments indicated that the cytolytic lymphocytes recognized closely related structures on the target cells. Phenotypically and functionally similar effector cells emerged after activation of PBL with the anti-CD3 MoAb OKT3. Taken together, the results indicate that activation of PBL with MoAb K46M induces cytotoxic cells that differ from classical NK cells but that resemble mature cytotoxic T lymphocytes (CTL). However, unlike CTL, cytotoxicity was not MHC-restricted and the conventional T-cell receptor complex (CD3/Ti) appeared not to be involved in target cell recognition and cytolysis.

Monoclonal antibodies against leucoagglutinin-reactive human T lymphocyte surface components. Two antibodies which inhibit cell-mediated cytotoxicity at a post-binding stage

Two out of 20 monoclonal antibodies (IgM, kappa), mAb 3192 and mAb K3G, raised against leucoagglutinin-reactive components on human T cells, effectively blocked lymphocyte-mediated cytotoxicity in vitro. No antigenic polypeptide reactive with these antibodies has been identified thus far. However, they have previously been shown to react specifically with certain neutral glycolipids obtained from spleen. Both mAb inhibited the cytotoxicity of natural killer (NK) cells against K562 cells, antibody-dependent cellular cytotoxicity (ADCC) towards antibody-coated bovine erythrocytes and cytotoxic T lymphocyte activity against allogeneic target cells. In both NK and ADCC, preincubation of the lymphocytes with different antibody concentrations resulted in a dose-dependent reduction of cytotoxicity. In contrast, preincubation of the target cells had no effect indicating that the mAb inhibited cytotoxicity at the effector cell level. When studied at the single-cell level, the mAb did not alter the number of lymphocytes forming conjugates with K562 but significantly reduced the frequency of conjugates containing dead target cells. Addition of the mAb to preformed conjugates resulted in a dose-dependent reduction in the proportion of conjugates containing dead target cells. Furthermore, mAb 3192 did not reduce the number of lymphocytes forming rosettes with bovine erythrocytes, indicating that inhibition of ADCC was not due to blocking of the effector cell-target cell interaction mediated by the Fc receptor of the effector cells. Taken together, these results suggest that the mAb inhibited cytotoxicity by interfering with a post-binding step common for the different cytotoxicity systems.

Inhibition of proliferative and cytotoxic activities of human T lymphocytes with rabbit antibodies directed against leucoagglutinin-reactive T cell surface components

Three rabbit antisera (870, 872 and 873) were raised against leucoagglutinin-reactive components from the surface of human T cells. The antibodies reacted with two major glycoproteins of 175 kDa and 105 kDa. None of the antibodies triggered peripheral blood lymphocytes or T cells to proliferation when tested under different culture conditions. All antibodies inhibited the proliferative response to concanavalin A or to allogeneic lymphocytes in mixed lymphocyte culture when whole IgG fractions were used. Complete inhibition of cytotoxic activity was obtained in cell-mediated lympholysis and in natural killer cell cytotoxicity (NK) when fresh peripheral blood lymphocytes were used as effector cells. Weak inhibition was also obtained in NK when mixed lymphocyte culture-activated effector cells were used. The inhibition was stronger, when NK activity was determined against MOLT4 target cells as compared to K562. Whereas F(ab')2 fragments of 873 IgG inhibited cytotoxic T lymphocyte activity completely, Fab fragments of 873 IgG neither inhibited proliferation nor cytotoxic T lymphocyte activity, but gave some inhibition of NK against MOLT4 targets. The results indicate that antibodies against these leucoagglutinin-reactive structures reacted with polypeptides similar to or identical with the human "leukocyte function-associated antigen-1" (LFA-1) considered to be an important mediator of cell-cell interactions and nonspecific adherence.

Transferrin receptors on mitogen-stimulated human thymus-derived lymphocytes

The appearance of transferrin receptors on mitogen-stimulated human thymus-derived (T) lymphocytes was studied. When indirect immunofluorescence with immunoadsorbent-purified antitransferrin antibodies was used, approximately 10% of resting T cells were stained. This proportion increased to 50-80% of the cells 3-4 days after stimulation with the mitogenic lectins concanavalin A (Con A) and leucoagglutinin (La) from Phaseolus vulgaris. Almost all blast cells (greater than or equal to 90%) were positive. Cell binding experiments with 125I-labelled transferrin indicated the presence of 1-5 x 10(5) transferrin receptor molecules/cell with high avidity for transferrin (K = 2 - 12 x 10(8) l/mol). Analysis by sodium dodecyl sulphate polyacrylamide gel electrophoresis and autoradiography of cell lysates containing 125I-labelled T-cell surface components revealed two surface peptides (90 kdaltons and 80 kdaltons, reducing conditions), which selectively bound to insolubilized antitransferrin antibodies. The 90-kdalton peptide also bound to insolubilized transferrin. The 80-kdalton peptide is most probably transferrin and the 90-kdalton peptide the transferrin receptor. Unreduced transferrin receptor had a molecular weight of 180 kdalton. It is probably a glycoprotein, since it reacted with wheat germ agglutinin, La, and probably also Con A. The properties of the lymphocyte transferrin receptor are similar to those described for transferrin receptors on various in-vitro-grown transformed cells. This speaks in favour of a common receptor present on all proliferating human cells.

Mitogenic leukoagglutinin from Phaseolus vulgaris binds to a pentasaccharide unit in N-acetyllactosamine-type glycoprotein glycans

The carbohydrate binding specificity of leukoagglutinin (La; Phaseolus vulgaris isolectin L4) was studied by using quantitative precipitation and precipitation-inhibition. A series of purified glycopeptides and synthetic oligosaccharides were used as inhibitors. The minimal structural unit required for La binding was the disaccharide GlcNac(1 leads to beta 2)Man. Additions for this basic unit of different sugar residues gave a positive or negative contribution to binding. The most complementary structure was the pentasaccharide (formula: see text). This pentasaccharide units occurs in tetraantennary N-acetyllactosamine-type glycoprotein glycans. Glycoproteins containing such structures were accordingly precipitated by La. Selected glycopeptides and oligosaccharides were also tested as inhibitors of La-induced DNA synthesis in human lymphocytes. The pattern of inhibition was essentially the same as that obtained by precipitation-inhibition, indicating that binding to lymphocytes via the carbohydrate binding site of the lectin is an essential step in the activation process.