Genes encoding tumor necrosis factor alpha and granzyme A are expressed during development of autoimmune diabetes

Progressive destruction of the insulin-producing beta cells in nonobese diabetic mice is observed after infiltration of the pancreas with lymphocytes [Makino, S., Kunimoto, K., Muraoka, Y., Mizushima, Y., Katagiri, K. & Tochino, Y. (1980) Exp. Anim. (Tokyo) 29, 1-13]. We show that the genes for tumor necrosis factor alpha and granzyme A, a serine protease associated with cytoplasmic granules of cytotoxic cells, are expressed during the development of spontaneous diabetes mellitus in the nonobese diabetic mouse. Granzyme A-positive cells are found both in and surrounding the islets, implying induction prior to islet infiltration. Tumor necrosis factor alpha expression is exclusively observed in the intra-islet infiltrate, predominantly in lymphocytes adjacent to insulin-producing beta cells, the targets of the autoimmune destruction, implying that tumor necrosis factor alpha expression is induced locally--i.e., in the islet. A considerable portion of cells expressing tumor necrosis factor alpha appear to be CD4+ T cells. This T-cell subset was previously shown to be necessary for development of the disease. Thus, these findings may be important for understanding the pathogenesis of autoimmune diabetes mellitus and potentially also for that of other T-cell-mediated autoimmune diseases.

Botryllus schlosseri (Tunicata) whole colony irradiation: do senescent zooid resorption and immunological resorption involve similar recognition events?

The colonial tunicate Botryllus schlosseri undergoes cyclic blastogenesis where feeding zooids are senescened and resorbed and a new generation of zooids takes over the colony. When non-identical colonies come into direct contact, they either reject each other or fuse. Fusion is usually followed by the resorption of one of the partners in the chimera (immunological resorption). The striking morphological similarities between the two resorption phenomena suggest that both may involve tissue destruction following self-nonself recognition events. Here we attempt to modify these two events by whole colony gamma irradiation assays. Three sets of experiments were performed: 1) different doses of whole colony irradiation for determination of irradiation effects (110 colonies, up to 8,000 rads); 2) pairs of irradiated-nonirradiated isografts of clonal replicates for the potential of reconstruction of the irradiated partners (23 pairs); 3) chimeras of irradiated-nonirradiated partners for analysis of resorption hierarchy. Mortality increased with the irradiation dose. All colonies exposed to more than 5,000 rads died within 19 days, while no colony died below 2,000 rads. The average mortality periods, in days, for doses of 6,000-8,000, 5,000, and 2,500-4,000 rads were 14.4 +/- 3.1 (n = 24), 19.8 +/- 6.0 (n = 15), and 19.6 + 5.1 (n = 22), respectively. Younger colonies (3-6 months old) may survive radiation better than older ones (more than 13 months). Many morphological alterations were recorded in irradiated colonies: ampullar contraction and/or dilation, accumulation of pigment cells within ampullae, abnormal bleeding from blood vessels, sluggish blood circulation, necrotic zones, reduction in bud number, and irregularities in zooid and system structures. With doses of 3,000-4,000 rads and above, irradiation arrested the formation of new buds and interrupted normal takeover, turning the colony into a chaotic bulk of vessels, buds, and zooid segments. Death supervened after a period of up to 1 month of poor condition, which was also characterized by loss of organization in systems. In isografts of irradiated-nonirradiated parts, the normal subclone resorbed all zooids and buds of the irradiated one within less than 1 week, even if it was up to 13 times smaller, without showing any sign of harmful effects. Thus, the irradiated subclone is not reconstituted by sharing blood circulation with a syngeneic part. Under 2,000 rads some of the irradiated zooids within this type of union started to regenerate, and at 1,000 rads no resorption was recorded, even though the number of zooids decreased in the irradiated part.(ABSTRACT TRUNCATED AT 400 WORDS)

Allorecognition histocompatibility in a protochordate species: is the relationship to MHC somatic or structural?

Colonial tunicates are complex marine invertebrates (in fact protochordates) that undergo a variety of histocompatibility reactions in their intraspecific competition for feeding surfaces. By means of these reactions colonies fuse with kin, extend domination over a feeding surface, while isolating unrelated conspecifics. The primary determinant of fusion (with kin) or rejection (of non-kin) is a single, highly polymorphic, histocompatibility gene locus (or haplotype), called Fu/HC. Following fusion with nonidentical kin sharing 1 or more Fu/HC allele(s), the fused pair expands both chimeric partners via an asexual budding process, further extending domination over a feeding surface. However, at some later time point an intense set of histoincompatibility reactions occurs between fused kin, resulting in the destruction of all individuals of one of the genotypes, ending the chimeric state. In this review we describe what is known of the genetics and several biological properties encoded by the Fu/HC, and the several independent gene loci that control the colony resorption phenomena that return the colony to the province of a single genotypic individual.

An immunodominant murine lymphoma cell surface heterodimer marks thymic progenitor subsets

mAb 1C11 was raised against the cells of retrovirus-negative, radiation-induced thymomas of C57BL/Ka mice. MAb 1C11 binds to radiation- and RadLV-induced C57BL/Ka lymphomas, to lymphomas of other mouse strains and to B-lineage tumors. The 1C11 Ag is expressed on a subpopulation of normal thymocytes that is enriched in immature cells. After fractionated x-irradiation, this percentage increases gradually during the preleukemic period, hence mAb 1C11 appears to identify a transformation-related cell surface molecule. This conclusion is supported by experiments demonstrating that flow microfluorimetry-sorted, 1C11-expressing preleukemic thymocytes progress rapidly to full neoplasia following intrathymic injection, whereas nonexpressing cells do not. Most of day-14 fetal thymocytes are as strongly positive as thymic lymphomas for the 1C11 Ag whereas Ag-activated T cell lines express moderate levels. Multiparameter flow microfluorimetry analysis shows that 1C11 is expressed predominantly on CD3-/lo thymic blast cells of three phenotypically defined subsets: CD4-8-, CD4-8+, and CD4+8+, all of which contain thymic progenitors. By immunohistochemical staining, the Ag is also found in association with epithelial cells on a variety of normal, nonlymphoid tissue, but is not detectable on heart tissue. The 1C11 antibody immunoprecipitates a disulfide-linked heterodimeric protein of 85/37 kDa and the antigenic determinant is located on the H chain of the molecule. When analyzed by SDS-PAGE under nonreducing conditions, the molecule exists as a 130-kDa protein. Enzymatic digestion of the heterodimer indicates that the H chain, but not the L chain, has at least three N-linked glycosylation sites. We propose that this novel cell surface glycoprotein may be associated with processes of differentiation and lymphomagenesis.

Structural similarity between a primitive chordate membrane heterodimer and lymphocyte antigen receptors

Botryllus schlosseri is a colonial tunicate that shared a common ancestor with the lineage leading to mammals about 450 million years ago, and flourishes today along the California coast. Prior studies of Botryllus populations have demonstrated the presence of a co-dominantly expressed, highly polymorphic histocompatibility locus (Fu/HC) controlling the acceptance (fusion) or rejection of new individuals into a parabiotic colony. Intercolonial blood cell contact, and recognition of self/not self, precedes both fusion and rejection reactions. Efforts to understand the evolution of the immune system necessitate study of cell surface molecules involved in cell-cell recognition events in primitive species. In mammals, birds, amphibians, and fishes clonally distributed lymphocyte surface molecules that are responsible for antigen recognition (B cell immunoglobulins and T cell receptors) can be distinguished by the disulfide linkage that pairs two or more polypeptides containing constant and variable regions. We have identified a disulfide-linked, heterodimeric (alpha beta) cell surface molecule in Botryllus with biochemical resemblance to mammalian lymphocyte antigen receptors. Observed charge variants of constituent chains of the tunicate protein described here do not correlate with Fu/HC allelic diversity. Both chains of this heterodimer can be resolved into several isoforms which are not based upon post-translational carbohydrate or phosphate additions. Comparisons of iodinated tryptic peptides from two beta chain isomorphs reveal one distinct and several common peptides.

The growth factor IL-7 induces expression of a transformation-associated antigen in normal pre-B cells

The B lineage antigen 6C3Ag is expressed by a number of cell types involved in lymphopoiesis. We have investigated whether there is a relationship between activation of normal pre-B cells by the growth factor IL-7 and the expression of 6C3Ag. Sorted sub-populations of bone marrow pre-B cells were cultured with IL-7 and their expression of surface antigens measured. There is a rapid induction of 6C3Ag expression after exposure to IL-7 by pre-B cells but not mature B cells. In particular, the 6C3lo pre-B cells respond very strongly by increasing 6C3Ag expression. The expression of 6C3Ag coincides with increased DNA synthesis and formation of lymphoblasts by the responding cells. The responses seen were specific to IL-7, and to a lesser degree IL-4. We conclude from this that IL-7 specifically induces the expression of 6C3Ag.

An immunodominant murine lymphoma cell surface heterodimer marks thymic progenitor subsets

mAb 1C11 was raised against the cells of retrovirus-negative, radiation-induced thymomas of C57BL/Ka mice. MAb 1C11 binds to radiation- and RadLV-induced C57BL/Ka lymphomas, to lymphomas of other mouse strains and to B-lineage tumors. The 1C11 Ag is expressed on a subpopulation of normal thymocytes that is enriched in immature cells. After fractionated x-irradiation, this percentage increases gradually during the preleukemic period, hence mAb 1C11 appears to identify a transformation-related cell surface molecule. This conclusion is supported by experiments demonstrating that flow microfluorimetry-sorted, 1C11-expressing preleukemic thymocytes progress rapidly to full neoplasia following intrathymic injection, whereas nonexpressing cells do not. Most of day-14 fetal thymocytes are as strongly positive as thymic lymphomas for the 1C11 Ag whereas Ag-activated T cell lines express moderate levels. Multiparameter flow microfluorimetry analysis shows that 1C11 is expressed predominantly on CD3-/lo thymic blast cells of three phenotypically defined subsets: CD4-8-, CD4-8+, and CD4+8+, all of which contain thymic progenitors. By immunohistochemical staining, the Ag is also found in association with epithelial cells on a variety of normal, nonlymphoid tissue, but is not detectable on heart tissue. The 1C11 antibody immunoprecipitates a disulfide-linked heterodimeric protein of 85/37 kDa and the antigenic determinant is located on the H chain of the molecule. When analyzed by SDS-PAGE under nonreducing conditions, the molecule exists as a 130-kDa protein. Enzymatic digestion of the heterodimer indicates that the H chain, but not the L chain, has at least three N-linked glycosylation sites. We propose that this novel cell surface glycoprotein may be associated with processes of differentiation and lymphomagenesis.

The early B lineage antigen BP-1 and the transformation-associated antigen 6C3 are on the same molecule

Biochemical similarities and cellular distribution patterns of the early B lineage-specific BP-1 alloantigen and the B lineage transformation-associated 6C3 Ag prompted this comparative study of the reactivities of the BP-1 and 6C3 mAb. Both Ag were found to be expressed on the same cells in normal tissues, and on the same cell lines when a large panel was analyzed. The Ag are both phosphorylated and have identical m.w., which may vary in different cell types because of differences in glycosylation. Immunoprecipitation of pre-B cell lysates with the BP-1 antibody removed the 6C3-reactive molecules and vice versa. However, the 6C3 antibody did not inhibit binding of the BP-1 antibody to viable cells and, in fact, enhanced immunofluorescence staining was observed when both antibodies were added together. These results indicate that the BP-1 and 6C3 antibodies react with different epitopes on the same molecule that is expressed in relatively low levels on normal early B lineage cells, and in relatively high levels on most neoplastic pre-B cells, pre-B cells in long term bone marrow cultures and certain stromal cell lines.

The early B lineage antigen BP-1 and the transformation-associated antigen 6C3 are on the same molecule

Biochemical similarities and cellular distribution patterns of the early B lineage-specific BP-1 alloantigen and the B lineage transformation-associated 6C3 Ag prompted this comparative study of the reactivities of the BP-1 and 6C3 mAb. Both Ag were found to be expressed on the same cells in normal tissues, and on the same cell lines when a large panel was analyzed. The Ag are both phosphorylated and have identical m.w., which may vary in different cell types because of differences in glycosylation. Immunoprecipitation of pre-B cell lysates with the BP-1 antibody removed the 6C3-reactive molecules and vice versa. However, the 6C3 antibody did not inhibit binding of the BP-1 antibody to viable cells and, in fact, enhanced immunofluorescence staining was observed when both antibodies were added together. These results indicate that the BP-1 and 6C3 antibodies react with different epitopes on the same molecule that is expressed in relatively low levels on normal early B lineage cells, and in relatively high levels on most neoplastic pre-B cells, pre-B cells in long term bone marrow cultures and certain stromal cell lines.

Intrathymic maturation of murine T lymphocytes from CD8+ precursors

The CD4-8- thymocyte subset contains immature precursors for phenotypically and functionally mature CD4+8- and CD4-8+ thymocytes and peripheral T cells, as well as nonmature CD4+8+ thymocytes, most of which die in situ. The intrathymic death of most thymocytes is probably related to selective influences that ensure that only those precursors bearing self-major histocompatibility complex (MHC)-restricted and self-tolerant T-cell antigen receptors (TCR) survive to complete the maturation process. Interactions between surface molecules on thymocytes (TCR, CD4, and CD8) and thymic stromal cells (MHC proteins) are critical to repertoire selection. To understand this process, the lineage relationships among immature, nonmature, and mature thymocytes must be defined. We have examined directly the precursor-progeny relationships among CD4+8-, CD4-8+, and CD4+8+ murine thymocyte subsets by assessing their short-term (less than 5 days) developmental potentials following intrathymic injection into Thy-1 congenic, unirradiated host mice. Our results identify TCR-/lo CD4-8+ and TCRlo CD4+8+ blast cells as sequential intermediates in the development of mature TCRhi CD4+8- and TCRhi CD4-8+ thymocytes from CD4-8- precursors, thus defining at least one intrathymic maturation pathway for T lymphocytes.

Measurement of binding specificity between T cell lymphomas and murine leukemia viruses

We have previously reported the presence of receptors on radiation leukemia virus (RadLV)-induced thymomas and malignant thymocytes from AKR mice which specifically bind retrovirus produced by these T cell clones. These receptors have been shown to have specificity for virus reminiscent of an immune-specific receptor. Previous studies on T cell lymphoma binding to retroviruses have involved measurement of the interaction of labelled virus with cells using fluorescence-activated cell sorter (FACS) analysis (McGrath et al., J. Virol. (1978) 25, 923; McGrath and Weissman, Cell (1979) 17, 65; Weissman and McGrath, Curr. Top. Microbiol. Immunol. (1982) 98, 103). Here we report development of an assay for measuring lymphoma binding to virus, prepared as an immunoabsorbent adhered to a microtiter plate. Using this assay, we have shown that only T and not B cell lymphomas can bind to T cell-tropic viruses, and some cell lines have greatest specificity for homologous virus. The AKR-derived T cell lymphomas, SL3 and KKT-2, show greater specificity for leukemogenic AKR viruses, than for an AKR xenotropic virus or the recombinant AKR virus, MCF247. The RadLV-induced T cell lines, C6VL/1 and BL/VL3, have been found to bind cross-reactively to several different murine leukemia viruses (MuLVs). RadLV-induced T cell lymphomas do have greater specificity for their cognate retroviruses since free, homologous retrovirus can best block the interaction between cells and virus adhered to the wells of a microtiter plate. Cross-reactive interactions are more easily demonstrated by this assay, probably because low avidity interactions are stabilized as a result of the mode of virus presentation. Binding specificity for retroviral envelope determinants has been demonstrated using a rat anti-retroviral antiserum prepared as an F(ab)1 fragment. This antiserum can inhibit the interaction between the C6VL/1 thymoma and its RadLV virus. Specificity of this antibody for a gp70-like protein was confirmed by NaDodSO4-polyacrylamide gel electrophoresis (PAGE) and by loss of this activity after absorption of antibody on virus. Antibodies specific for RadLV/VL3 gp70 determinants can inhibit the interaction of C6VL/1 with RadLV/VL3 suggesting that cross-reactive binding to heterologous virus is also specific for a gp70 viral env determinant.

Human homologue of mouse lymph node homing receptor: evolutionary conservation at tandem cell interaction domains

A cDNA clone homologous to the mouse lymph node homing receptor core protein (mLHRc) was isolated from a cDNA library derived from stimulated human peripheral blood lymphocytes. Human RNA blot analysis shows a tissue and cell-line distribution of transcript expression generally parallel to that seen in the mouse, with expression confined to lymphoid tissues and some cell lines. Genomic DNA analysis suggests a low-copy gene under high-stringency conditions. The complete nucleotide sequence predicts a mature protein of 334 amino acids, identical in length to mLHRc. The protein shows striking conservation globally between human and mouse sequences. In particular, all three genre of protein interaction domains identified in the mouse--an animal lectin domain, an epidermal growth factor (EGF)-like domain, and two homologous repeat units preserving the motif of complement regulatory proteins (CRP)--are present in the human protein (hLHRc), and maintain the same tandem arrangement. The lectin and EGF-like regions are the most homologous, while the CRP domains are less conserved between species. The two CRP units in hLHRc are distinct from those in mLHRc in that they are homologous to one another rather than identical, suggesting strong pressure for maintenance of two repeats in this molecule. hLHRc is distinct from other kinds of lymphocyte adhesion molecules represented by VLA-4 (integrin) or CD44/gp90Hermes and, together with mLHRc and two other recently described molecules having a similar domain motif, defines a novel class of adhesion molecules exhibiting distinct evolutionary features. We propose that hLHRc likely represents the protein core of the human homologue of mLHRc functionally as well as structurally.

Developmental potential of CD4-8- thymocytes. Peripheral progeny include mature CD4-8- T cells bearing alpha beta T cell receptor

We have used the intra-thymic transfer system to investigate the population dynamics of thymocyte and mature T cell subsets in the absence of continuing precursor input from the bone marrow. We have followed the development and life span of CD4+ and CD8+ thymocyte subsets and mature peripheral T cells from intra-thymically injected adult or fetal CD4-8- thymic precursors. Both precursor types proliferated, differentiated, and exported to peripheral lymphoid tissues alpha beta-TCR+CD4+8- and CD4-8+ progeny which formed a stable, long-lived component of the peripheral T cell pool. The production of phenotypically mature thymocytes and peripheral T cells occurred more rapidly from fetal CD4-8- precursors. CD4+8-:CD4-8+ ratios among peripheral progeny of intra-thymically-injected CD4-8- precursors were initially normal, but they steadily declined among progeny of the fetal precursors. Thus, there appear to be differences in the life span and/or proliferative capacity of mature T cells derived from embryonic vs adult progenitors. In addition to the predominant CD4+8- and CD4-8+ subsets of peripheral T cells, a minor (1 to 20%) population of Thy-1+CD3+4-8- T cells was identified among peripheral progeny of intra-thymically-injected CD4-8- thymocytes, as well as in lymph nodes of unmanipulated animals. A total of 20 to 34% of this subset expressed V beta 8+ TCR and the majority were CD5hi, Pgp-1+, and J11d-. The function and specificity of this newly identified population of thymically derived peripheral T cells remains to be investigated.

Mouse hematopoietic stem-cell antigen Sca-1 is a member of the Ly-6 antigen family

Recently, hematopoietic stem cells were purified to homogeneity from mouse bone marrow. The protein structure of Sca-1, the cell surface antigen used in the isolation of hematopoietic stem cells, is described here. It is shown that the Sca-1 antigen is a member of the Ly-6 antigen family. The anti-Sca-1 antibody was used in immunohistochemistry experiments to define the structures in several tissues that had previously been shown to contain Ly-6 antigens. In thymus, spleen, and kidney, specific staining of parenchymal cells can be demonstrated, whereas only vasculature reacts with anti-Sca-1 in brain, heart, and liver and possibly in lung.

Identification of a novel bone marrow-derived B-cell progenitor population that coexpresses B220 and Thy-1 and is highly enriched for Abelson leukemia virus targets

A novel stage in early B-lymphocyte differentiation has been identified in normal mouse bone marrow cells. Earlier work had demonstrated that bone marrow cells characterized by low levels of Thy-1 and lack of a panel of lineage markers (Thy-1lo Lin- cells) were highly enriched for pluripotent hematopoietic stem cells. In this paper, we present evidence that another bone marrow population, which expressed low levels of Thy-1 and coexpressed B220, a B-lineage-specific form of the leukocyte common antigen, contained early and potent precursors for B lymphocytes upon in vivo transfer to irradiated hosts. These Thy-1lo B220+ cells, comprising 1 to 2% of bone marrow cells, were enriched for large cells in the mitotic cycle; the population lacked significant pluripotent hematopoietic stem cell activity and myeloid-erythroid progenitors. Most strikingly, Thy-1lo B220+ cells represented a highly enriched population of bone marrow cells that could be targets of Abelson murine leukemia virus transformation. We propose that Thy-1lo B220+ bone marrow cells represent the earliest stage of committed lymphocyte progenitors, intermediate in differentiation between Thy-1lo Lin- pluripotent stem cells and, in the B lineage, Thy-1- B220+ pre-B cells.

Developmental potential of CD4-8- thymocytes. Peripheral progeny include mature CD4-8- T cells bearing alpha beta T cell receptor

We have used the intra-thymic transfer system to investigate the population dynamics of thymocyte and mature T cell subsets in the absence of continuing precursor input from the bone marrow. We have followed the development and life span of CD4+ and CD8+ thymocyte subsets and mature peripheral T cells from intra-thymically injected adult or fetal CD4-8- thymic precursors. Both precursor types proliferated, differentiated, and exported to peripheral lymphoid tissues alpha beta-TCR+CD4+8- and CD4-8+ progeny which formed a stable, long-lived component of the peripheral T cell pool. The production of phenotypically mature thymocytes and peripheral T cells occurred more rapidly from fetal CD4-8- precursors. CD4+8-:CD4-8+ ratios among peripheral progeny of intra-thymically-injected CD4-8- precursors were initially normal, but they steadily declined among progeny of the fetal precursors. Thus, there appear to be differences in the life span and/or proliferative capacity of mature T cells derived from embryonic vs adult progenitors. In addition to the predominant CD4+8- and CD4-8+ subsets of peripheral T cells, a minor (1 to 20%) population of Thy-1+CD3+4-8- T cells was identified among peripheral progeny of intra-thymically-injected CD4-8- thymocytes, as well as in lymph nodes of unmanipulated animals. A total of 20 to 34% of this subset expressed V beta 8+ TCR and the majority were CD5hi, Pgp-1+, and J11d-. The function and specificity of this newly identified population of thymically derived peripheral T cells remains to be investigated.

Peyer's patch-specific lymphocyte homing receptors consist of a VLA-4-like alpha chain associated with either of two integrin beta chains, one of which is novel

Lymphocytes home to various lymphoid organs by adhering to and migrating through specialized high endothelial venules (HEV). The murine cell surface heterodimer LPAM-1 is involved in the homing of lymphocytes to mucosal sites (Peyer's patches). LPAM-1 has an alpha subunit (alpha 4m) analogous to the alpha chain of the human integrin molecule VLA-4. Here we show that the LPAM-1 beta subunit (beta p) is immunochemically and biochemically distinct from previously defined integrin beta subunits, suggesting that beta p represents a novel integrin beta subunit. Depending on the cellular source two alternative beta subunits, beta p and integrin beta 1, can be isolated in association with alpha 4m. Therefore, alpha 4m is the common subunit of the unique integrin LPAM-1 (alpha 4m beta p) and of the heterodimer LPAM-2 (alpha 4m beta 1), which is analogous to VLA-4. Antibody-blocking experiments suggest that, in addition to LPAM-1, LPAM-2 is also involved in the organ-specific adhesion of lymphocytes to Peyer's patch HEV.

IL-2 induces expression of serine protease enzymes and genes in natural killer and nonspecific T killer cells

The expression of serine protease genes was examined in murine NK cells that were purified by panning spleen cells with PMA. Although unstimulated NK cells were cytolytic, they were found not to express the C11 (chymotrypsin-like) mRNA. Culturing these cells in IL-2 (500 to 800 U/ml) for 5 to 7 days induced both the lytic activities and the protease enzymes by 20- to 30-fold. Concomitant to these activation events, the total steady state mRNA of both C11 and HF (trypsin-like) genes were also elevated. The activation of lysis, serine protease enzymes, and C11 and HF mRNA all peaked around day 5 in culture and was dose dependent. In order to exclude the possibility that PMA synergizes with IL-2 in this system, spleen cells from SCID mice, which contained mainly NK cells, were cultured under the same conditions (800 U/ml IL-2, with or without PMA) and PMA did not appear to enhance the expression of these mRNA. Similarly, IL-2 also induced the lytic activities, enzyme levels, and mRNA in the non-Ag-specific T killer cells isolated from spleens of normal mice. Lytic activity of T killer cells was not as high as the NK cells, however, the addition of PHA into the lytic assay resulted in enhanced lysis comparable to that of NK cells. These results showed that lytic activity increased along with protease enzyme levels and mRNA expression in both NK and resting T cells. Therefore, elevated levels of the protease enzymes could be one mechanism involved in optimal lytic activity of IL-2-induced lymphokine activated killer cells.

IL-2 induces expression of serine protease enzymes and genes in natural killer and nonspecific T killer cells

The expression of serine protease genes was examined in murine NK cells that were purified by panning spleen cells with PMA. Although unstimulated NK cells were cytolytic, they were found not to express the C11 (chymotrypsin-like) mRNA. Culturing these cells in IL-2 (500 to 800 U/ml) for 5 to 7 days induced both the lytic activities and the protease enzymes by 20- to 30-fold. Concomitant to these activation events, the total steady state mRNA of both C11 and HF (trypsin-like) genes were also elevated. The activation of lysis, serine protease enzymes, and C11 and HF mRNA all peaked around day 5 in culture and was dose dependent. In order to exclude the possibility that PMA synergizes with IL-2 in this system, spleen cells from SCID mice, which contained mainly NK cells, were cultured under the same conditions (800 U/ml IL-2, with or without PMA) and PMA did not appear to enhance the expression of these mRNA. Similarly, IL-2 also induced the lytic activities, enzyme levels, and mRNA in the non-Ag-specific T killer cells isolated from spleens of normal mice. Lytic activity of T killer cells was not as high as the NK cells, however, the addition of PHA into the lytic assay resulted in enhanced lysis comparable to that of NK cells. These results showed that lytic activity increased along with protease enzyme levels and mRNA expression in both NK and resting T cells. Therefore, elevated levels of the protease enzymes could be one mechanism involved in optimal lytic activity of IL-2-induced lymphokine activated killer cells.

Analysis of naturally occurring delayed-type hypersensitivity reactions in leprosy by in situ hybridization

Analysis of tissue lesions of the major reactional states of leprosy was undertaken to study the immune mechanisms underlying regulation of cell-mediated immunity and delayed-type hypersensitivity (DTH) in man. In situ hybridization hybridization of reversal reaction biopsy specimens for INF-gamma mRNA expression revealed a 10-fold increase in specific mRNA-containing cells over that observed in unresponsive lepromatous patients. Expression of huHF serine esterase, a marker for T cytotoxic cells, were fourfold increased in reversal reaction and tuberculoid lesions above that detected in unresponsive lepromatous individuals. Immunohistology of reversal reactions confirmed a selective increase of Th and T cytotoxic cells in the cellular immune response. Of interest, the microanatomic location of these serine esterase mRNA-containing cells was identical to the distribution of CD4+ cells. Analysis of erythema nodosum leprosum (ENL) lesions revealed differences in the underlying immune processes in comparison with reversal reaction lesions. Although phenotypic Th cells predominated in ENL lesions, IFN-gamma and serine esterase gene expression were markedly reduced. We suggest that reversal reactions represent a hyperimmune DTH response characterized by a selective increase of CD4+ IFN-gamma producing cells and T cytotoxic cells, which result in the clearing of bacilli and concomitant tissue damage. In contrast, ENL reactions may be viewed as a transient diminution of Ts cells and activity leading to a partial and transient augmentation in cell-mediated immunity, perhaps sufficient to result in antibody and immune complex formation, but insufficient to clear bacilli from lesions.

Relative V beta transcript levels in thymus and peripheral lymphoid tissues from various mouse strains. Inverse correlation of I-E and Mls expression with relative abundance of several V beta transcripts in peripheral lymphoid tissues

We have measured the relative levels of transcripts for 15 of the 22 known V beta gene segments. The level of transcripts for the highest and lowest expressed V beta gene segment differed by greater than 20-fold in the thymus and an even larger difference was observed in the periphery. The levels of expressions were unrelated to the order of the V beta genes on the chromosome. For most of the V beta gene segments, the relative transcript levels were the same in the thymus and periphery, suggesting that thymic selection in general does not act solely upon the V beta gene segment. One V beta gene segment in the BALB and B10 mice strains was an exception to this rule. V beta 5.2 expression in the periphery of BALB and B10 mice inversely correlated with the expression of the MHC class II molecule I-E. Five V beta gene segments had reduced transcript levels in the periphery of Mls-1a mice compared with their thymic levels or to the levels found in Mls-1b mice. The peripheral level of V beta 3 transcripts vary with MHC and Mls-2 haplotypes. The observation that certain V beta transcript levels are reduced in the periphery when compared with the thymus favors the hypothesis that self tolerance at the T cell level results in the elimination of self-reactive T cells, rather than paralysis by a block at some post-transcriptional step. Finally, the wide variability of V beta gene segment expression in the thymus suggests mechanisms exist to import an early bias to the repertoire. Whether this bias results from differential V beta segment rearrangement rates, differential V beta expression rates, or events occurring after TCR-alpha/beta expression on immature/nonmature thymocyte cell surfaces is yet to be determined.

Integrin molecules involved in lymphocyte homing to Peyer's patches

This review summarizes experiments designed to analyze lymphocyte receptors mediating recognition of and adhesion to HEV in mucosal lymphoid organs. A monoclonal antibody (R1-2) was selected which inhibits the adhesion of murine lymphocytes to Peyer's patch HEV. Antibody R1-2 recognizes the alpha chain (alpha 4m) of the murine lymphocyte cell-surface alpha beta heterodimer LPAM-1. The association of LPAM-1 alpha and beta chains requires the presence of Ca++ ions. Two proteins of Mr 84,000 and 62,000 which are also precipitated by antibody R1-2 most likely represent fragments of alpha 4m. The cross-reactivity of a monospecific rabbit anti-serum indicated that alpha 4m is analogous to the alpha chain of the human integrin molecule VLA-4. In addition, a cDNA clone encoding the human VLA-4 alpha chain hybridized with RNA from alpha 4m+ but not alpha 4m- cell lines. However, the LPAM-1 beta subunit (beta p) was shown to be immunochemically and biochemically distinct from integrin beta 1, beta 2, and beta 3, indicating that beta p represents a unique integrin beta chain. When the beta subunits associated with alpha 4m on a panel of lymphoma cell lines were analyzed, it was found that, depending on the cellular source, alpha 4m can associate with either of two beta chains: beta p or integrin beta 1. Therefore alpha 4m appears to be the common subunit of the two lymphocyte cell surface heterodimers LPAM-1 (alpha 4m/beta p) and LPAM-2 (alpha 4m/beta 1). LPAM-2 is analogous to the human VLA-4 molecule, whereas LPAM-1 represents a unique integrin heterodimer. Antibody R1-2 inhibited Peyer's patch HEV-adhesion of normal mouse lymphocytes and every lymphoma cell line tested including LPAM-1 and LPAM-2 single-positive cell lines. We also showed that the binding capacity of variants of a clonal lymphoma cell line to Peyer's patch HEV correlates with the level of LPAM-1 expression. It therefore appears that both heterodimers are involved in lymphocyte-Peyer's patch HEV interactions and that the adhesion of lymphocytes to Peyer's patch HEV is generally LPAM-1- or LPAM-2-dependent. We further investigated whether VLA-4, the human analog of LPAM-2, can mediate adhesion of human lymphocytes to HEV in mucosal lymphoid organs.(ABSTRACT TRUNCATED AT 400 WORDS)

Mouse lymph node homing receptor cDNA clone encodes a glycoprotein revealing tandem interaction domains

Isolation of a clone encoding the mouse lymph node homing receptor reveals a deduced protein with an unusual protein mosaic architecture, containing a separate carbohydrate-binding (lectin) domain, an epidermal growth factor-like (EGF) domain, and an extracellular precisely duplicated repeat unit, which preserves the motif seen in the homologous repeat structure of complement regulatory proteins and other proteins. The receptor molecule is potentially highly glycosylated, and contains an apparent transmembrane region. Analysis of messenger RNA transcripts reveals a predominantly lymphoid distribution in direct relation to the cell surface expression of the MEL-14 determinant, and the cDNA clone is shown to confer the MEL-14 epitope in heterologous cells. The many novel features, including ubiquitination, embodied in this single receptor molecule form the basis for numerous approaches to the study of cell-cell interactions.

Two monoclonal antibodies identify thymic-repopulating cells in mouse bone marrow

The progenitor cells in the bone marrow that home to and repopulate the thymus have been incompletely characterized. In particular, it is not clear whether thymocytes differentiate directly from pluripotent hemopoietic stem cells that seed to the thymus, or whether T lymphoid-committed stem cells (prothymocytes) arise in the bone marrow before the thymic migration. In order to resolve this question, we have used mAb specific for cell-surface Ag to identify the bone marrow cells which can seed to and repopulate the thymus of irradiated mice. We report here that the majority of thymic-repopulating cells in mouse bone marrow express low levels of the Thy-1 Ag (Thy-1lo) plus high levels of a newly described Ag termed stem cell Ag (Sca-1). Two distinct populations of thymic-repopulating Thy-1loSca-1+ cells in mouse bone marrow can be discriminated based on expression of any of a number of hemolymphoid lineage-specific (Lin) markers. Thus, Thy-1loLin-Sca-1+ and Thy-1loLin+Sca-1+ fractions of bone marrow contain thymic-repopulating cells. A second Ag, stem cell Ag-2 (Sca-2), is expressed by Thy-1loLin+Sca-1+ cells but not by Thy-1loLin-Sca-1+ cells. The Thy-1loLin-Sca-1+ fraction expresses intermediate levels of the phagocyte glycoprotein-1 Ag, and comprises 30% of the Thy-1loLin- bone marrow cells, which have previously been shown to be highly enriched in pluripotent hemopoietic stem cells. By facilitating the isolation of highly purified subpopulations of bone marrow cells that can repopulate the thymus, Sca-1 and Sca-2 should provide an experimental tool for describing the developmental potential of such bone marrow subsets.