EXPRESSION AND PRESENTATION OF ENDOGENOUS MOUSE MAMMARY-TUMOR VIRUS SUPERANTIGENS BY THYMIC AND SPLENIC DENDRITIC CELLS AND B-CELLS

Tolerance against superantigens (SAgs) encoded by endogenous mouse mam mary tumor virus (Mtv) loci involves the intrathymic deletion of SAg-r eactive T cells expressing a particular TCR Vp-chain, presumably upon presentation of the SAg by specialized APC, However, although the role of dendritic cells (DC) in the induction of tolerance against convent ional Ags has been demonstrated, little is known about the role played by DC in tolerance induction against Mtv SAgs. Moreover, there is con flicting evidence concerning the capacity of DC to express and present Mtv SAgs. In this report we have analyzed the expression of Mtv SAgs in highly purified thymic and splenic DC and B cells by reverse transc riptase-PCR, using primers amplifying Mtv SAg-specific spliced mRNAs. DC express Mtv SAgs at levels comparable to B cells, but display a dif ferential expression pattern of the various Mtv loci compared with B c ells, Furthermore, our results show that DC are able to induce the del etion of SAg-reactive thymocytes in an in vitro assay, indicating that Mtv SAgs are functionally expressed on the DC surface. Collectively, our data are consistent with the hypothesis that DC play a role in the induction of intrathymic tolerance to Mtv SAgs.