Biological immunological and genetic characterization of specific suppressor T cells and their receptors immune to antigens of the H-2 complex. Clonal structure, narrow specificity of receptors and genetic restriction of specific T-suppressor function

Utilization of the MHC class I (H-2Kb) purified molecule and its synthetic peptides for inhibition of Kb-specific suppressor T cells and their induction in vivo by the MHC peptides

Six synthetic peptides of the MHC class I molecule corresponding to individual H-2Kb participants in amino acid sequences of domains alpha 1 (peptide 1 and 2) and alpha 2 (peptides 3, 4, 5, 6) were selected. Kb-specific suppressor T cells (Ts) were induced in vivo in mice, then pretreated with a set of peptides and assayed by proliferation decrease in a three-cell lymphocyte culture (MLC). The effector function of Ts was abolished by the complex of the alpha 2-domain peptides (but not by the alpha 1-domain peptides) and decreased by particular peptides separately (4, 5, 6) of the alpha 2-domain. Both alpha 1- and alpha 2-domain peptides, added in high concentration, decreased otherwise efficient enrichment of Ts during the absorption-elution procedure on the syngeneic macrophage (M psi) monolayers. A similar significant effect was observed using the purified Kb molecule (100 micrograms/ml) in the allogeneic M psi monolayer. Interaction between Ts receptors and some MHC peptides indicates in effector Ts activation in vivo by induction with peptides 5 and 6 of the alpha 2-domain. The fine mechanisms of interaction between MHC class I molecule epitopes and T-cell receptors of each of the T-cell subsets separately are presently being studied.

Difference between antigen-binding receptor repertoires in effector cytotoxic T lymphocytes and their secondary precursors (memory cells) specific to H-2Kb

The fine specificity of antigen-binding receptors was compared in pCTL-2 and secondary effector CTL (cytotoxic T lymphocytes) induced in vivo with the H-2Kb alloantigen in recombinant inbred mice. The lymphocyte preparations were enriched by elution from macrophage monolayers of various origins, including the donor (B6 strain), the H-2Kb mutant bm1, the H-2Kk allele B10.A(4R) and the recipient strain B10.D2(R101) as a control. Anti-Kb pCTL-2 eluted from third-party bm1 or B10.A(4R) monolayers gave rise to CTL progeny that lysed, equally well, both donor TC and those third-party TC from whose monolayer the pCTL-2 had been eluted, but which were unable to lyse irrelevant third-party TC. The lytic activities of secondary CTL whose precursors had been eluted from bm1 or B10.A(4R) monolayers were 6 and 12 times lower, respectively, than pCTL-2 eluted from the donor monolayer. Opposite results were shown for receptors of enriched secondary anti-Kb effector CTL. Irrespective of their elution source, whether donor, mutant or allele variant, the eluted effector CTL were able to lyse the donor TC to a similar degree and much more than the given third-party TC; moreover, they retained cross-reactivity in all cases. It is suggested that CTL receptors are homogeneous in specificity for a whole composite immunodominant epitope and differ from each other only in the affinity/lability of the combining site. In contrast, pCTL-2 can be separated into fractions: receptors of each fraction are strictly specific (with high affinity) to a particular portion of the same composite CTL epitope. It seems likely that the pCTL-2 receptor antigen-binding site is modified during pCTL-2 in vivo differentiation into effector CTL.

Inactivation of specific anti-H-2 suppressor T cells by antisera to I-J and I-C subregion products of the H-2 complex

Two antisera to Ia antigens, products of the H-2 complex I-Cd and I-JkEk subregions, respectively, have been obtained by immunization of the F1 hybrids of recombinant strains of mice. These antisera are shown to display a 50% cytotoxic effect in vitro, in the presence of complement, upon lymphocyte populations immune to the H-2-complex antigens and enriched for specific suppressor T cells (SSTC) by fractionation on a monolayer of target cells. The specificity of anti-Ia cytotoxins is shown by cross-antibody absorption with T and B cells of mice originating from the recombinant H-2 haplotypes and bearing either particular I-Cd, I-Jk and I-Ek antigens, or their combinations. Anti-I-Cd cytotoxins were found to react with both B and T cells, but at a different rate, and the anti-I-JkEk serum contains two antibody types directed to I-Ek and I-Jk products, respectively, the latter being able to react preferently with T cells. Although both antisera do inactivate the in vitro SSTC function in the presence of complement to a similar degree, the inactivating action of the anti-I-Cd serum, but not that of the anti-I-JkEk serum, occurs without complement. SSTC are shown to bear both Ia-antigens, I-J and I-C, as shown by both inactivation of the anti-suppressor effect of the antisera absorbed with spleen cells of different H-2 origin, and variation of the H-2 origin of SSTC pretreated with the intact antisera. It is suggested that these two markers, located on the same SSTC, function differently in SSTC immune to the H-2 antigens, and I-C antigen expression on the SSTC surface is presumed to be required for their interaction with the inhibited responder T cells proliferating in MLC.

Computer-assisted analysis of in vivo cytotoxic T cell responses

An approach has been devised for analysing data generated in the study of in vivo cytotoxic T cell responses. The method calculates the total number of lytic units generated in the peritoneal cavity, or in cultures of the lymph nodes draining the rear footpad, following antigenic stimulation. The assessment of group differences is facilitated, and the method lends itself to computerised and hence objective data analysis.

Suppression of delayed-type hypersensitivity to third party "bystander" alloantigens by antigen-specific suppressor T cells

Delayed-type hypersensitivity (DTH) against alloantigens can be induced by sc immunization with allogeneic cells. The induction of DTH can be suppressed by iv preimmunization of the mice with similar allogeneic spleen cells, provided the cells are irradiated before injection. This suppression is mediated by T cells. The suppressor activity can be induced not only by H-2-and non-H-2-coded antigens, but also by H-2 subregion-coded antigens. Suppression induced by K, I, or D subregion-coded antigens is specific for that particular subregion as well as for its haplotype. I-J-coded alloantigens were found to not be necessary for the induction of antigen-specific suppressor T cells. After restimulation of suppressor T cells by the "specific" alloantigens, the DTH to simultaneously administered third-party alloantigens becomes suppressed as well. This nonspecific suppression of DTH to third party "bystander" alloantigens also occurs when the specific and the third-party antigens are presented on separate cells, provided that both cell types are administered together at the same site. The simultaneous presentation of both sets of alloantigens during the induction phase of DTH only is sufficient to prevent the normal development of DTH to the third-party antigens.

Regulatory mechanisms in cell-mediated immune responses. Role of I-J and I-C determinants in the activation of H-2I and H-2K/D alloantigen-specific suppressor T cells

The role of individual H-2I subregion determinants in the activation of H-2I alloantigen-primed mixed leukocyte response suppressor T cells (MLR Ts), as well as their possible expression on stimulator cells required to trigger primed H-2K- or D-specific MLR Ts, was addressed in these studies. Both genetic and serologic studies demonstrated that MLR Ts potentially primed to alloantigens encoded by the entire H-2I region were triggered to MLR Ts factor production only by stimulator cells bearing the priming I-J and/or I-C, but not I-A or I-E alloantigens. The relevant I-J and I-C determinants were demonstrated on a single antigen-presenting cell population that is used in common by independent I-J-specific and I-C-specific MLR Ts. Unexpectedly, the stimulator cell population necessary to trigger MLR Ts primed to class I H-2K or D alloantigens expressed not only the priming class I determinant, but in addition, I-C alloantigens syngeneic with the MLR Ts haplotype. Stimulator populations bearing the appropriate H-2K or D alloantigen but serologically depleted of I-C+ cells or genetically constructed to display MLR Ts-disparate I-C determinants were ineffective stimulators of class I antigen-primed MLR Ts. Thus these data suggest that as allogeneic determinants, I-J- and I-C-encoded molecules are together the major triggering elements for MLR Ts primed to disparate H-2I region determinants. In addition, self-I-C molecule recognition appears to constitute an important feature of the triggering, and by implication, priming process of H-2 class I antigen-specific Ts cells.

Specificity of immunoglobulin E in coccidioidomycosis and correlation with disease involvement

Serum immunoglobulin E (IgE) antibodies were quantitated in 26 patients with active pulmonary coccidioidomycosis, 59 patients with active disseminated disease, 12 patients in clinical remission, and 91 healthy subjects. Significant differences were obtained in IgE serum levels of patients with active disease versus healthy subjects (P less than 0.0001). Patients with pulmonary coccidioidomycosis did not differ in their IgE levels when compared with patients with disseminated disease. However, serum IgE levels were significantly increased in patients with disease involving two or more organ systems when compared with patients with pulmonary disease or extrapulmonary disease involving a single organ system (P less than 0.02). Total serum IgE correlated with anti-Coccidioides IgE (P less than 0.001), but with only six exceptions, patients with anti-Coccidioides IgE also exhibited IgE antibodies to 1 or more of 12 common allergens. The correlation between hyperproduction of IgE and disease severity coupled with the depressed cell-mediated immune status of patients with this disease suggests a defect(s) in the T-lymphocyte population which functions to regulate IgE synthesis.

Requirement for the location of both appropriate and irrelevant H-2 antigens on the same stimulator cell for unspecific DNA-synthesis inhibition by the H-2-antigen-primed, specific suppressor T cells

Specific suppressor T cells (SSTC), primed in vivo with H-2 antigens, have been shown previously to inhibit DNA synthesis in the one-way, three-cell mixed lymphocyte reaction (MLR) provided that (a) the stimulator cells bear the priming H-2 antigens, and (b) the responder cells possess IC + S regions homologous to those of the SSTC. Anti-B10.A B10.A(2R) SSTC (anti-Dd) and anti-A.AL A.TL SSTC (anti-Kk) are shown here to be able to inhibit the DNA synthesis triggered in MLR, not only by the corresponding antigens, Dd and Kk, respectively, but also by irrelevant, third-party H-2 and Mls products provided that the corresponding and third-party antigens are presented on the same stimulator cell. If stimulator H-2 regions, whose products interact with SSTC and responders, are located on different stimulator cells within the particular MLR, SSTC activity is not elicited. Participation of cytotoxic T lymphocytes in DNA-synthesis suppression is ruled out. Direct contact or location of the inhibited responder cell very close to SSTC is considered to be required for the development of SSTC activity.

Requirements for induction of specific suppressor T cells and detection of their H-2 antigen-binding receptors by fractionation on target cell monolayers

The MC-resistant specific suppressor T cells that inhibit DNA synthesis and CTL generation in MLC were induced in vivo by gamma-irradiated allogeneic lymphoid cells in a large dose. MLRs were inhibited only slightly when triggered by third-party cells, even neighbouring with the corresponding stimulators. Unlike the irradiated cells, intact allogeneic lymphoid cells induced a mixture of macrophage-like and T-cell suppressors with a pronounced non-specific component of the action. Syngeneic cells induced low active non-specific suppressors of macrophage type only. The suppression was not due to a cytotoxic effect, since specific T suppressors differed from CTL by conditions of induction and high sensitivity to gamma-irradiation and from CTL precursors by high sensitivity to CY and HC. The specific T-suppressors could be selectively removed by adherence to a macrophage monolayer of the corresponding donor. The subsequent elution of adherent lymphocytes with pronase resulted in enrichment of specific T suppressors by a factor of 30 and 2.6, as judged by reduction in the number of lymphocytes required for 50% inhibition of DNA synthesis and 33% inhibition of CTL generation, respectively. The high specificity of this enrichment is shown by using both syngeneic monolayers for fractionation and third-party stimulators in MLR for testing and by disappearance of slight non-specific suppression caused by non-fractionated suppression. Complete inactivation of the eluted suppressors with anti-Thy-1.2 and anti-T antibodies, their resistance to anti-Mls antibodies, carrageenin, and carbonyl iron, together with the data of autoradiographic study and total DNA synthesis in the population indicate that the eluted highly specific suppressors represent mainly DNA-synthesizing large and medium T lymphocytes.