Altered I-J phenotype in E alpha transgenic mice

Cryptococcal capsular polysaccharide utilizes an antigen-presenting cell to induce a T-suppressor cell to secrete TsF

A T-T hybridoma (F6.6.2) which secretes a T-suppressor factor (TsF) specific for cryptococcal capsular polysaccharide (glucuronoxylomannan, GXM) was tested to determine if antigen-presenting cells (APC) were necessary for activation of the hybridoma to secrete TsF. Normal, syngeneic spleen cells were required along with GXM before TsF could be detected in culture supernatants. Ts cells did not secrete TsF unless the APC were obtained from mice which were identical at the "so-called' I-J sublocus as defined by the difference between B10.A(3R) and B10.A(5R) mice. The APC was adherent and could be depleted from spleen cell suspensions by treatment with anti-I-J and complement but not anti-I-A and complement. Additionally, treatment with anti-T cell serum or anti-immunoglobulin and complement did not remove the APC function of the spleen cell population. A role for I-E antigens in the function of the APC was determined by blocking antigen presentation to the suppressor cell with anti-I-E antibodies. The polysaccharide was associated with splenic adherent cells as extensive washing of the APC after incubation with GXM did not eliminate the antigen presenting function of the population.

A murine macrophage line of the H-2d/f haplotype can activate H-2k suppressor T cells

Little is known about the molecular basis for activation of suppressor T cells. In this report we describe two macrophage cell lines, BAC1.2.SC8 and its variant progeny B26, that differ in their ability to activate suppressor T cells. The SC8 line is derived from a (BALB/c x A.CA)F1 (H-2d/f) mouse and is haploid with respect to I-Ed. It is capable of activating I-Ed-restricted helper T cells as well as poly-(Glu50Tyr50)-specific I-Ed-restricted suppressor cells. The B26 variant can activate H-2d-restricted helper T cells but activates H-2k-restricted suppressor cells. The I-Ed molecules of SC8 and of B26 have identical amino acid sequences. This suggests that suppressor T cells either recognize posttranslational modifications of the I-E molecule or that there is another accessory molecule that helps determine the major histocompatibility complex restriction in the activation of suppressor T cells.

Unique mixed lymphocyte-stimulating determinants in Ed alpha gene-introduced C57BL/6 transgenic mice

A unique mixed lymphocyte-stimulating determinant(s) was detected in Ed alpha gene-introduced C57BL/6 transgenic mice using alloreactive T-cell clones. Such unique determinant(s) was not detected by primary mixed lymphocyte culture reactions. The possibility that such unique determinant(s) was created by the combinatorial association of Ed alpha transgene products with endogenous Ab beta gene products is discussed.

Suppressor T cells, antigen-presenting cells and the role of I-J restriction in oral tolerance to ovalbumin

Suppressor T cells (Ts) and antigen-presenting cell (APC) activity are both important for the induction of systemic tolerance after feeding protein antigens to mice. In this report, we have examined further the nature of the inter-relationship between Ts and APC in oral tolerance to ovalbumin (OVA). We found previously that oral tolerance to OVA could prevented by treating mice with oestradiol, and we now report that oestradiol enhances the ability of spleen APC to present OVA to T cells. In parallel, mice treated with oestradiol do not generate the Ts activity normally found after feeding OVA. Treatment of mice with anti-I-J antiserum prevents the induction of both tolerance and Ts activity after feeding OVA, but the suppressor effector cells generated by feeding OVA can not be depleted in vitro by treatment with anti-I-J antibody plus complement. In vivo administration of monoclonal anti-I-A antibody had no effect on oral tolerance to OVA. Our results show that induction of oral tolerance to OVA is an I-J-restricted phenomenon and we propose that this reflects an interaction between specific Ts cells and a population of I-J+ cells which we suggest are APC.

Epitopes associated with major histocompatibility complex (MHC) restriction site of T cells. IV. I-J epitopes on MHC-restricted cloned T cells

We studied the expression of an I-Jk epitope on class II-restricted cloned L3T4+ T cells established from H-2k, H-2b, F1 and semiallogeneic radiation bone marrow chimeras by the inhibition of antigen-induced T cell proliferation and in vitro secondary antibody response, and by the direct immunofluorescence with a monoclonal anti-I-Jk. Both I-Ak- and I-Ek-restricted T cells were shown to carry the identical I-Jk epitope regardless of their genotypic origins, antigen specificity, and helper or suppressor function. None of the I-Ab-restricted clones derived from similar animals showed the I-Jk epitope. This isomorphism, regardless of the restriction specificity for I-Ak or I-Ek, contradicts the idea that I-J is an idiotypic determinant on class II-restricted T cell antigen receptor (TcR). In fact, the I-Jk epitope was not comodulated with TcR/T3 complex when incubated with an anti-T3 antibody, indicating that I-J is a new isomorphic receptor for self different from TcR alpha/beta heterodimers.

Epitopes associated with MHC restriction site of T cells. III. I-J epitope on MHC-restricted T helper cells

I-J epitopes were found to be associated with the functional site of the class II MHC-restricted helper T (Th) cells: Virtually all of the H-2k-restricted Th cell function of H-2kxbF1 T cells was inhibited by the anti-I-Jk mAb, leaving the H-2b-restricted function unaffected. The I-Jk epitope was inducible in Th cells of different genotype origin according to the environmental class II antigens present in the early ontogeny of T cells. Although above results suggested that I-J is the structure reflecting the inducible MHC restriction specificity, further studies revealed some interesting controversies: First, the I-J phenotype did not always correlate with the class II restriction specificity, e.g., I-Ab-restricted Th from 5R was I-Jk-positive, whereas I-Ak-restricted Th of 4R was not. Second, there was no trans expression of parental I-J phenotypes and restriction specificities in F1 Th, e.g., the I-J phenotype was detected only on I-Ab-restricted Th of (4R X 5R)F1, whereas it was absent on I-Ak-restricted Th. This strict linkage between the restriction specificity and I-J phenotype was also found on Th cells developed in bone marrow chimera constructed with intra-H-2-recombinant mice. The expression of I-Jk was always associated with the restriction specificity of the relevant host. Thus, the restriction specificity of Th cells followed the host type, and the I-J expression on Th was exactly the same as that expressed by the host haplotype. These results indicate that I-J is an isomorphic structure adaptively expressed on Th cells that is involved in the unidirectional regulatory cell interactions, and that the polymorphism cannot be explained merely by the restriction specificity of the conventional T cell receptor heterodimer.