Regulatory mechanisms in cell-mediated immune responses. VI. Interaction of H-2 and non-H-2 genes in elaboration of mixed leukocyte reaction suppressor factor

Immunogenetic studies of spontaneous abortion in mice. II. Antiabortive effects are independent of systemic regulatory mechanisms

CBA/J females (H-2k) mated with DBA2/J males (H-2d) exhibit a high rate of fetal resorption. Fetal survival has been improved by pretreatment of CBA/J females with spleen cells from BALB/c J (H-2d) (but not from CBA/J or DBA/2/J) males. Similarly, three out of nine recombinant inbred strains (recombining BALB/c and DBA2 genomes at the homozygous state) possess antiabortive effects like the BALB/c parent. Previous studies showed that BALB/c pretreatment triggers the appearance of suppressor cells in the spleen and of IgG1 anti-H-2d antibodies in the serum of CBA/J females. Studies of these two immunological parameters after CBA/J preimmunization by the different recombinant strains suggest that local intrauterine immunoregulation is the determinant of success or failure of allopregnancy.

Regulatory T cells in pregnancy. III. Comparison of early acting and late acting suppressor T cells in MLR: evidence for involvement of differential T-cell subsets

The properties of mitomycin-treated and untreated spleen cells from allopregnant mice (bearing allogeneic foetuses) have been compared for suppressive activity of mixed lymphocyte reaction (MLR) of maternal strain spleen cells responding to paternal (or genetically related) strain cells. Mitomycin-treated cells in 1% normal mouse serum suppress an MLR if added at its onset while they cannot alter an already set up (day 2) MLR. Conversely untreated spleen cells are unable to affect an MLR if added at its onset while they suppress it when added on day 2 of an ongoing MLR. The two systems also differ in their in vitro retriggering requirements at the target cell (stimulator) level. Whereas the untreated, late acting population, in a k/d or k/a system, requires the contact with molecules coded by 'S-G' (or IC+S G) subregion, also present in the father's strain, the mitomycin-treated, early acting population, tested on similar panel does first appear non-specific. Suggestive evidence, however, is given that this apparent non-specificity may in fact veil clones of cells with specific recognition of 'private' Ia determinants. It is suggested that allopregnant mice elaborate two T suppressor cells, acting at different steps of the MLR. The usefulness of the first set (mitomycin-resistant suppression) for exploring the Ia chart is pointed out.

Regulation of human cytotoxic lymphocyte responses. I. Non-cytolytic suppression mediated by alloantigen-activated cells

Alloantigen sensitized human lymphocytes obtained from a 2-3 day mixed lymphocyte culture (MLC) suppressed the in vitro generation of alloreactive cytotoxic lymphocytes (CTL). The inhibition of CTL responses was demonstrated in MLC after both 1 day and 14 days' allosensitization. The suppressor cells were nylon wool non-adherent, lacked Fc receptors and adhered to histamine columns. The MLC-activated suppressor cell population had an associated very low and transient cytotoxic response directed against the allogeneic sensitizing cell. Several procedures were used to dissociate this activity from suppressor cell function: (1) donors were preselected which showed minimal cross-killing between allogeneic stimulating cells, (2) suppressor cultures were added to the test cultures prior to the development of maximal CTL activity, (3) suppressor cultures were irradiated preventing cell proliferation associated with differentiating CTL. Lastly, by increasing stimulating antigen concentration suppressor cell activity was increased rather than being competitively diminished, which would be predicted if suppression was occurring through a cytolytic or inactivation of stimulating antigen. It was therefore concluded that alloantigen stimulation in MLC activates a non-cytolytic regulatory cell population which is capable of inhibiting CTL responses to third-party allogeneic lymphocytes.

Regulation of human cytotoxic lymphocyte responses. II. Suppression by a soluble factor produced by primed lymphocytes

A soluble supernatant factor is elaborated from in vitro primed human allogeneic lymphocytes which suppresses the development of alloreactive cytotoxic lymphocytes (CTL). In contrast, supernatants obtained from primary mixed lymphocyte cultures (MLC) and primed autologous cultures were unable to suppress CTL activation, indicating that antigen restimulation was required to elicit the factor. The suppressor factor (SF) functioned in a dose-dependent manner. When the SF was added 24 or 48 hr after MLC initiation it was ineffective. However, adding the SF at culture initiation significantly reduced CTL activity, suggesting that suppression occurs either during antigen recognition or early in the CTL differentiation pathway. The SF did not function by altering the kinetics of the CTL response. Preincubation experiments showed that the SF operates by partially inactivating both MLC responder and stimulator cell populations.

The immune response to human type III and type V (AB2) collagen: antigenic determinants and genetic control in mice

The genetic influences on the specific IgG antibody response to helical antigenic determinants of native soluble type III and V (AB2) human collagen have been studied in mice. H-2-linked Ir genes have been detected for each of these collagens, as have background effects. The alleles controlling high antibody responses can be distinguished from those previously described for bovine collagen type I and type I propeptide. Apparent two-gene complementation in the response to type V (AB2) may indicate that this antigen will be a useful probe in further studies of the complex nature of antigen presentation for T cell recognition. The present studies may facilitate the production of specific, high-affinity monoclonal antibodies for the human collagens which, in turn, will facilitate the study of connective tissue biology and pathology.

Antigen-specific T cell-mediated suppression. V. H-2-linked genetic control of distinct antigen-specific defects in the production and activity of L-glutamic acid50-L-tyrosine50 suppressor factor

The occurrence of distinct genetic defects affecting the generation of T cell-derived suppressor factor (TsF) or the suppressive activity of such TsF was investigated. For the synthetic polypeptide L-glutamic acid50-L-tyrosine50 (GT), it could be shown that the nonsuppressor strain A/J fails to produce suppressor T cells (Ts1) capable of GT-TsF generation upon challenge with GT. Conversely, B6, another nonsuppressor strain, produces GT-TsF active on other allogeneic strains such as A/J, but itself fails to be suppressed by this material. (B6A)F1 mice both make GT-TsF, and are suppressed by it. Further experiments revealed that the production of GT-TsF and the ability to be suppressed by GT-TsF are under the control of H-2-linked genes. Finally, the defect in GT-TsF activity in B6 mice was shown to be exquisitely antigen specific, in that this strain can be suppressed by a closely related TsF specific for L-glutamic acid60-L-alanine30-L-tyrosine10. It is suggested that H-2 (I) control of suppressor T cell (Ts) activity may reflect the involvement of I-A and I-C gene products in antigen presentation to Ts in analog with other T cell subsets, and that TsF function might also involve such presentation, in this case of the idiotypic structures of the TsF-combining site. Predictions deriving from this hypothesis are discussed, including the possibility that H-2 linked immune response genes regulate auto-anti-idiotypic responses in immune networks.

Soluble factors in tolerance and contact sensitivity to 2,4-dinitrofluorobenzene in mice. III. Histocompatibility antigens associated with the hapten dinitrophenol serve as target molecules on 2,4-dinitrofluorobenzene-immune T cells for soluble suppressor factor

Previous studies have shown that suppression of 2,4-dinitrofluorobenzene (DNFB) contact sensitivity by soluble suppressor factor (SSF) requires that the donor of immune lymph node (LN) cells and of SSF share either the H-2K and/or H-2D region of the major histocompatibility complex. Thus, target or acceptor molecules for SSF appear to be coded for by genes within the H-2K and H-2D loci. Experiments were done to investigate the nature of these target molecules and to determine what cell types expressed them. It was found that purified lymph node T cells are suppressed by SSF indicating that T cells express the acceptor molecules. Adsorption experiments showed that the only cells capable of adsorbing the suppressor factor are DNFB-immune T cells from donors which share with the factor-producing strain either the H-2K or H-2D locus. This adsorption can be specifically blocked by pretreating the immune LN cells with antibodies directed against H-2K and/or H-2D determinants or against the hapten DNP but not by antibodies against Ia or theta-antigens. Collectively, these results indicate that the target molecules are expressed only by DNFB-immune T cells and are comprised of histocompatibility antigens associated with DNP.

Regulatory mechanisms in cell-mediated immune responses. VII. Presence of I-C subregion determinants on mixed leukocyte reaction suppressor factor

The presence of H-2 gene products on mixed leukocyte reaction (MLR) supressor factor was investigated by passage of MLR-suppressor factor (SF) over solid immunoadsorbents prepared with various anti-H-2 subregion sera. Antisera with specificity for all or certain I subregion determinants removed or significantly reduced suppressor activity; adsorption was not consistent with K or D region specificity. The single I subregion specificity common to all adsorbing preparations was I-C. Serologic differentiation of I-C products of k and d haplotypes expressed on MLR-SF was established with antisera prepared in I-Cd/I-Ck disparate strain combinations. These sera define allelic T cell restricted Lad determinants encoded by I-C genes. MLR-SF prepared from (BALB/c X CBA)F1 mice and exposed to the I-Cd and I-Ck specific adsorbents demonstrated d and k haplotype specific adsorption respectively. F1 suppressor activity adsorbed on an anti-I-Cd column was eluted by glycine-HCl buffer and suppressed only BALB/c (H-2d) responses. B10.A suppressor activity was removed by anti-I-Cd sera, but was unaffected by anti-I-Ck sera, indicating that B10.A suppressor activity is encoded by an I-C subregion derived from the d haplotype. Antisera with anti-I-Jk specificity did not remove suppressor activity of various H-2k factors. Finally, adsorption with antisera directed against H-2-associated determinants of the allogeneic cell used to stimulate suppressor factor generation demonstrated that sensitizing alloantigens are not components of MLR suppressor factor. Thus among the major histocompatibility complex (MHC)-controlled suppressor factors, MLR suppressor factor is uniquely determined by the I-C subregion.