T cells that recognize peptide sequences of self MHC class II molecules exist in syngeneic mice.

T cell reactivity toward self MHC class II molecules has been recognized in syngeneic MLR in a number of studies, where the T cells are believed to recognize the combination of self/nonself peptide and self MHC molecule. We investigated the stimulation of T cell proliferation by synthetic peptides of sequences corresponding to the first polymorphic amino terminal domain of alpha- and beta-chains of self I-A molecules. Both unprimed and primed T cells responded to a number of peptides of alpha 1 and beta 1 domains of self I-Ad molecules. The response was dependent on the presentation of I-Ad peptides by syngeneic APC and was blocked by anti-class II MHC mAb. Upon further investigation it was observed that I-Ad peptides could inhibit the stimulation of Ag-specific MHC class II-restricted T cell hybridoma due to self presentation of peptides rather than to direct binding of free peptides to the TCR, further supporting their affinity/interaction with intact self MHC class II molecules. The peptide I-A beta d 62-78 showed high affinity toward intact self MHC II molecule as determined by the inhibition of Ag-specific T cell stimulation and yet was nonstimulatory for syngeneic T cells, therefore representing an MHC determinant that may have induced self tolerance. Thus we have shown that strong T cell proliferative responses can be generated in normal mice against the peptides derived from self MHC class II molecules and these cells are part of the normal T cell repertoire. Therefore complete tolerance toward potentially powerful immunodominant but cryptic determinants of self Ag may not be necessary to prevent autoimmune diseases.

HLA Bw57 and DR7 association with psoriasis vulgaris in south India.

Eighty-three south Indian patients with psoriasis vulgaris were studied for HLA antigen frequencies and compared with 77 controls studied simultaneously. HLA Bw57, a split of B17 was found elevated in the patients. The two sexes differed in their age-at-onset curves: females had a preponderance to early onset of the disease, while the males had late onset. Among these patients, major group 3, a Western Brachycephal Armenoid group, revealed the highest risk for B17 & Bw57 but not major group 2, a Mediterranean one.

Structural, functional relationship of thymus derived cells of the lizard Calotes versicolor.

Structural and functional characteristics of the lymphoid cells of Calotes versicolor were studied using thymocytes and splenocytes isolated on a buoyant density gradient and adherence column. The isolated cells were treated with anti-Calotes thymocytes serum (ATS) and their residual capacity to effect antigen specific migration inhibition and antibody production assessed. Results revealed that antigen specific migration inhibition effector cells could be enriched in less dense nylon wool-adherent fraction and 95% of this fraction were sensitive to ATS. Antigen specific plaque forming cells (PFC) could also be enriched in the same fraction but they were not susceptible to ATS.

Characteristics of heterologous anti lizard (Calotes versicolor) thymocyte serum which identify the functions of thymus-derived cell lineage.

In an attempt to study the functions of thymus derived cell lineage, two different heterologous anti-lizard thymocyte sera (ATS i.v. & ATS i.p) were raised by immunizing rabbits with viable thymocytes of Calotes versicolor. Cytotoxicity assay, nylon wool fractionation and thymectomy were employed to assess the effect of these ATS on lymphoid cells of the lizards. The results revealed that ATS i.v. contained minimum amount of irrelevant antibodies than ATS i.p; non-adherent splenocytes were enriched with ATS sensitive cells, whereas the adherent with SIg+; adult thymectomy decreased ATS sensitive cells in spleens and the density of thymic antigen (identified by the ATS) in splenic thymus derived cell lineage was much higher than on thymocytes themselves. The cells of thymic lineage identified by the ATS thus resemble those of higher vertebrates.

Studies on T-cells of the lizard, Calotes versicolor: adherent and non-adherent populations of the spleen.

The Nylon-wool adherent and non-adherent populations of splenocytes obtained from both normal and immunized lizards were subjected to treatment with heterologous anti-thymocyte serum (ATS) and their capacity to migrate in-vitro out of capillary tubes and to mediate cell mediated immunity (CMI) as adjudged by migration inhibition method studied. It was found that the non-adherent splenocytes migrate faster and this migration is inhibited by ATS treatment. Further, the property of mediating antigen specific migration inhibition (MI) resides with this non-adherent population and this property is abolished by ATS treatment. In contrast, the adherent splenocytes migrate little, do not mediate MI and are not susceptible to ATS. It is clear from the study that the non-adherent splenocyte population is enriched for ATS sensitivity and that the same population from immunized lizards is effective in inhibiting migration of indicator splenocytes in the presence of antigen. These cells may very well be a population of T-cells similar to that of higher vertebrates.