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23 CD45 IN $i T CELL GENERATION: DISRUPTION OF CWS-EXON 6 DOES NOT AFFECT Vy3 DENDRITIC EPIDERMAL TCELL DEVELOPMENT. m HFuiisawa. Division of Demtalology, Sunnvbrook Health Science Cent% University of Toronto, Toronto, Canada

There are two distinct lineages of T cells: ? cell receptor (TCR) up-bearing cells (up T cells) and TCR #+ainS cells (@ T cells). All of the aB T cells and most subs& of yS T cells develop in lbe thymus. It has been demonstrated lhal the protein tyrosine phosphatw CD45 plays a pivotal role in the intnuhymic development of ~$3 T cell. Thymwyte maturation is arrested at the lmnsilional stage from immature CD4+ CD8+ double positive to mature CD4+ or CDS+ single positive cells after CWS-exon 6 gene dii~ption. In Ibis study, we examined whether Vy3 dendritic epidamal T cells (DETC) and Vy2 T cells, two subsets of thymus-dependent yS T cells, are altered in the CWS-exon 6-delicient mice. In situ immunolabelling on epidermal sheets demonstrated that CD45-deficient mice had a normal density and immunophemnype of Vy3 DETC compared lo the wild-type control mice. RT-PCR revealed that Vr3 TCR mRNA was mesent in tie eoidermis of CD45-deficient mice and wild-type cbntmls. Flow cytom&y demonst&d no significant difference in the proportion of V@ T cells in lhe epidermis. and no significant difference in Vy2 T cells in lhe lymph nodes existing between lbe two genotypes. Our results indicate lhal although CD45 is crucial for the development of c$ T cells, this molecule is not necessary for the thymic maturation of y& T cells including Vy3 DETC and Vy2 T cells.