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E M Shevach

Publications and source records attributed to E M Shevach.

At least 217 records · Page 12Linked to original sources
PubMed1977

The guinea pig I region. I. A structural and genetic analysis.

The Ia antigens of the guinea pig have been shown to play a central role in the regulation of the immune response. We have previously partially characterized the chemical structure of these antigens. In this communication, we further characterize the structure of the five Ia antigens already described, as well as two new Ia antigens. Evidence is presented which shows that these seven Ia antigens can be organized into three distinct groups, each with a characteristic structure. The Ia.2 determinant of strain 2 and the Ia.3 and Ia.5 determinants of strain 13 animals are found on molecules composed of a 25,000 dalton chain and a 33,000 dalton chain in noncovalent association, or else are individually expressed on nonlinked 33,000 and 25,000 dalton molecules. The Ia.4 and Ia.5 determinants of strain 2 and the Ia.7 determinant of strain 13 are borne on 58,000 dalton molecules in which two chains are linked by disulfide bonds. The Ia.1 and Ia.6 determinants of strain 13 are found on a molecule of 26,000-27,000 daltons. Ia.6 of strain 2 has yet to be definitively assigned. Furthermore, in strain 13 animals the Ia.3 and Ia.5 determinants are borne on the same molecule, as are the Ia.1 and Ia.6 determinants. In strain 2 animals, the Ia.4 and Ia.5 determinants are found on the same molecule. On the basis of chemical structure, we have divided the guinea pig I region into three subregions. The accompanying paper presents evidence of associations between particular Ia genes and Ir genes.

Animals↗
PubMed1977

The guinea pig I region. II. Functional analysis.

We have examined whether an association exists between specific Ia antigen genes and Ir genes which are encoded within the same haplotype. Functionally monospecific sera to the Ia antigens of the guinea pig MHC were selective in their ability to inhibit antigen-specific T-cell proliferation and we were thus able to demonstrate an association between individual Ia specificities and specific Ir genes. The results of these studies in inbred animals were confirmed by examining the association of Ir genes and Ia antigens in the outbred guinea pig population. Of great interest was the observation that antisera made against cross-reactive Ia antigens of strains lacking specific Ir genes would still inhibit immune responses of strains possessing the Ir gene, if the Ir gene was associated with that Ia antigen in the responder strain.

Albumins↗
PubMed1977

Nature of the antigenic complex recognized by T lymphocytes II. T-cell activation by direct modification of macrophage histocompatibility antigens.

In order to analyze the molecular structures involved in T-cell recognition we developed an in vitro primary response against alloantisera bound to histocompatibility antigens in which nonimmune guinea pig T cells can be sensitized and subsequently challenged in tissue culture with antisera-treated macrophages. If macrophages were incubated with alloantisera directed against the I-region-associated (Ia) antigens of the guinea pig major histocompatibility complex (MHC) T cells could be sensitized to the antisera bound to macrophage Ia determinants. Anti-Ia-treated syngeneic macrophages in the first and second cultures elicited specific T-cell activation, as measured by increased DNA synthesis, to the antisera-induced immunogenic determinants. Similarly, antiIa-treated allogeneic macrophages also specifically stimulated T cells to antisera bound to allogeneic Ia determinants while reducing the mixed leukocyte reaction. Antisera to the B.1 antigens of the guinea pig MHC, the homologue of the mouse H-2K or H-2D antigens, also elicited specific T-cell activation that did not cross-react with that produced by the anti-Ia alloantisera. Furthermore, the anti-B.1-induced stimulation appeared to be associated with the Ia antigens of the macrophage used for priming since (2 x 13)F1 T cells sensitized with anti-B.1-treated parental macrophages could be restimulated only with the parental macrophage used for initial sensitization, and not with those of the other parent. Since the parental strain 2 and strain 13 guinea pigs express serologically identical B.1 antigens and differ only by Ia antigens of the MHC, this observation suggests that both B.1 and Ia antigens may be included in the immunogenic complex recognized by T cells. However, we cannot rule out the possibility that this restriction is due to other genetic differences between strain 2 and strain 13 guinea pigs that is unrelated to the I-region. We interpret these findings as showing that macrophage Ia antigens may serve to directly present antigens bound to the Ia molecule, and possibly indirectly aid in the presentation of antigens bound to other membrane components, such as the B.1 antigens.

Animals↗
PubMed1977

Independent populations of primed F1 guinea pig T lymphocytes respond to antigen-pulsed parental peritoneal exudate cells.

Thymus-dependent (T) lymphocytes from (2 x 13)F1 hybrid guinea pigs immunized to ovalbumin (OVA) in complete Freund's adjuvant can be stimulated to proliferate in vitro by antigen-pulsed peritoneal exudate cells (PECs) derived from either strain 2 or strain 13 donors. In this communication, we show that the population of primed F1 T lymphocytes which can be activated by antigen-pulsed strain 2 PECs is largely independent of the population of cells that can be activated by antigen-pulsed strain 13 PECs. This was demonstrated by both positive and negative selection procedures. In the former, T lymphocytes from OVA-primed (2 x 13)F1 donors were enriched by initial culture with OVA-pulsed strain 2 or strain 13 PECs for 1 wk. Cells selected by culture with OVA-pulsed strain 2 PECs responded well to OVA-pulsed strain 2 PECs and poorly to OVA-pulsed strain 13 PECs. If positive selection had been carried out with OVA-pulsed strain 13 PECs, the selected F1 T cells responded well to OVA-pulsed 13 PECs and poorly to OVA-pulsed 2 PECs. Negative selection was achieved by short term culture with antigen-pulsed PECs and by eliminating proliferating cells by treatment with bromodeoxyuridine and light. This procedure demonstrated that the population of primed F1 T lymphocytes which are responsive to OVA or to purified protein derivative of tuberculin can be divided into subpopulations uniquely responsive to antigen on either strain 2 or strain 13 PECs. Evidence was presented to indicate that this selective responsiveness was not the result of the action of alloantigen-specific suppressor cells. The results are considered in terms of current concepts of the genetic and molecular regulation of the interaction of PECs and T lymphocytes.

Animals↗
PubMed1977

Nature of the antigenic complex recognized by T lymphocytes: specific sensitization by antigens associated with allogeneic macrophages.

Alloreactive guinea pig thymus-derived (T) cells generated in vitro were rendered unresponsive to allogeneic macrophages by treatment with bromodeoxyuridine and light. The remaining T cells were subsequently primed and rechallenged in tissue culture with trinitrophenyl (Tnp)-modified syngeneic or allogeneic macrophages. By this procedure we found that the remaining T cells primed with Tnp-modified allogeneic macrophages could be restimulated only with Tnp-modified allogeneic, not syngeneic, macrophages. Similarily, if the remaining T cells were primed with Tnp-modified syngeneic macrophages, they could be restimulated only by Tnp-modified syngeneic, and not by allogeneic, macrophages. In contrast, no T cell sensitization with Tnp-modified syngeneic or allogeneic macrophages occurred if the alloreactive T cells were treated with light alone, suggesting that an uninhibited mixed leukocyte reaction causes nonspecific suppression of antigen-specific T cell priming. These results indicate that the genetic restriction of T cell-macrophage interactions is imposed by the type of macrophage used for initial sensitization rather than by a requirement for self-recognition through cellular interaction structures.

Animals↗
PubMed1977

The expression of Ia antigens on immunocompetent cells in the quinea pig. I the differential expression of Ia antigens on T cell subpopulations.

We have examined the effect of negative selection with anti-Ia serum and C on a number of T cell functions and have clearly defined two subpopulations of guinea pig T lymphocytes. One subpopulation is susceptible to the lytic effects on anti-Ia serum and C and includes the majority of the primed T cells which proliferate and which produce migration inhibition factor in response to specific antigen stimulation in vitro. The lytic effects of anti-Ia serum were directed against the antigen-specific T cell and not an accessory cell such as a macrophage or nonantigen-specific T cell. No evidence for allelic exclusion of the Ia antigens of the antigen-responsive cell could be demonstrated. The susceptibility of the mitogen-responsive T cell to lysis by anti-Ia serum and C varied with the mitogen used, anatomic origin of the T cell, and the strain of animals studied. A second subpopulation of T cells is completely resistant to the lytic effects of anti-Ia serum and C and includes the primed T helper cell and the T cell that proliferates in response to alloantigenic stimulation in the MLR.

Animals↗
PubMed1977

The expression of Ia antigens on immunocompetent cells in the guinea pig. II. Ia antigens on macrophages.

Only 15 to 25% of purified oil-induced guinea pig macrophages could be lysed by treatment with anti-Ia serum and C. Those cells remaining alive after treatment were not damaged and were metabolically active since they readily phagocytized latex beads. However, the "Ia-negative" macrophages were markedly deficient in their ability to present protein antigens to immune T lymphocytes and to function as stimulator cells when mixed with allogeneic T cells in the mixed leukocyte reaction. It thus appears that Ia antigens are expressed on a subpopulation of macrophages and that this subpopulation plays a critical role in the activation of T cell proliferation to soluble protein antigens and to alloantigens.

Animals↗
PubMed1977

The role of the macrophage as the stimulator cell in contact sensitivity.

In this study we examined the requirement for the type of stimulator cell for thymus-derived (T) lymphocyte activation to simple chemical haptens. T cells from picryl chloride-immune guinea pigs were challenged in vitro with various trinitrophenyl (TNP)-conjugated syngeneic stimulator cells and the extent of activation was determined by an increase in DNA synthesis. Hapten-specific T cell activation occurred with TNP-conjugated peritoneal exudate cells (PEC) and purified macrophages but not with TNP-conjugated erythrocytes, thymocytes, or nonadherent lymph node cells or PEC. In addition, T cell activation also occurred with TNP-conjugated guinea pig leukemia cells, but only in the presence of macrophages. Furthermore, it was shown that macrophages were required to process and/or present TNP-conjugated leukemia cell antigens rather than simply providing a growth-promoting function. These results suggest that a macrophage-like stimulator cell is required for hapten-specific T cell activation and that this particular stimulator cell may be important in contact sensitivity.

Animals↗
PubMed1977

Induction of guinea pig antibody responses in vitro.

Guinea pig spleen cells cultured together with peritoneal exudate lymphocytes (PEL) were found to generate large numbers of antibody-forming cells (AFC) in vitro in response to hapten-protein antigens. Neither cell type cultured alone yielded appreciable responses. Strain 13 or F1 (Strain 2 X Strain 13) lymphocytes, but not those from strain 2 animals, are able to respond to the genetically controlled antigen, DNP-guinea pig albumin (DNP-GPA). Antisera directed against responder (strain 13) parent Ia antigens selectively blocked the generation of AFC by F1 (strain 2 X strain 13) spleen-PEL mixtures in response to DNP-GPA. Both allogeneic (strain 2) and syngeneic macrophages functioned equally well in presentation of DNP-GPA to strain 13 lymphocytes.

Animals↗
PubMed1977

Nature of the antigenic complex recognized by T lymphocytes. IV. Inhibition of antigen-specific T cell proliferation by antibodies to stimulator macrophage Ia antigens.

We have previously demonstrated that nonimmune guinea pig T lymphocytes could be specifically sensitized with TNP-modified allogeneic macrophages after eliminating the alloreactive T cells with bromodeoxyuridine (BUdR) and light treatment. This procedure allowed the unique opportunity to use anti-Ia sera directed against the Ia antigens of only the stimulator macrophages or responder T cells to determine against which cell type anti-Ia would block TNP-specific stimulation. It was found that the TNP-specific DNA synthetic response of BUdR and light-treated T cells stimulated with TNP-modified allogeneic macrophages was totally eliminated by anti-Ia sera directed solely against the allogeneic stimulator macrophage. In contrast, anti-Ia sera directed only against the responder T cells had no effect on their response to TNP-modified allogeneic macrophages. These findings indicate that macrophage Ia antigens are required for efficient T cell-macrophage interactions and raise the possibility that T cell Ia antigens may not be required for collaboration with macrophages. This latter possibility was substantiated by experiments in which we show that treating T cells with anti-Ia sera and complement to remove the Ia-positive cells either before or after priming, or both, had no effect on their ability to be primed and restimulated with TNP-modified macrophages.

Animals↗
PubMed1977

Immune responses of outbred guinea pigs to the sequential polymer poly(L-Tyr-L-Glu-L-Ala-Gly): association of response to strain 13 histocompatibility locus.

Outbred Hartley guinea pigs were immunized with the sequential polymer poly(L-Tyr-L-Glu-L-Ala-Gly) (T-G-A-Gly)n, the random copolymer poly(Glu50,Tyr50) (GT), and a low dose of dinitrophenylated guinea pig albumin (DNP-GPA). Only the guinea pigs that carry strain 13 histocompatibility antigen responded to these three antigens as measured by the antigen-binding assay and delayed skin reaction. The immune response (Ir) genes controlling responses to (T-G-A-Gly)n, GT, or DNP-GPA, were found to be distinctive genes. Nonresponder inbred strain 2 guinea pigs were able to produce anti(T-G-A-Gly)n antibodies when immunized with (T-G-A-Gly)n and methylated bovine serum albumin (MBSA) complex, although there was no delayed skin reaction and in vitro cultured lymphocytes did not respond. The in vitro response to (T-G-A-Gly)n of cultured lymphocytes from responder animals was inhibited by strain 2 antistrain 13 alloantisera but not the strain 13 anti-strain 2 alloantisera.

Alanine↗
PubMed1976

Nature of the antigenic complex recognized by T lymphocytes. I. Analysis with an in vitro primary response to soluble protein antigens.

In order to analyze the genetic factors involved in the regulation of macrophage-T-cells interaction we have developed an in vitro primary response to soluble protein antigens in which nonimmune guinea pig T cells can be sensitized and subsequently challenged in tissue culture with antigen-pulsed macrophages. Antigen-specific T-cell activation, as measured by increased DNA synthesis, occurred when syngeneic antigen-pulsed macrophages were used for both initial sensitization and secondary challenge. No T-cell activation occurred when allogeneic antigen-pulsed macrophages were used for secondary challenge of cells primed when syngeneic macrophages. When allogeneic antigen-pulsed macrophages were used in both primary and secondary cultures it was difficult to assess antigen-specific stimulation due to the substantial mixed leukocyte reaction. However, when T cells from F1 animals were primed with parental antigen-pulsed macrophages they responded only to the parental macrophages used for initial sensitization but not to those of the other parent. These results are discussed with respect to T-cell recognition of a complex antigenic determinant which may include I-region gene products.

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