Bovine insulin(BI)-specific I-Ab-restricted T cell clones have been characterized for fine specificity and TCR gene usage. We have demonstrated that mouse strains carrying H-2b on three different genetic backgrounds (C57BL, BALB, and 129) rearrange and express the V beta 6 gene in a large proportion (36%) of insulin-specific clones. In these strains, the non-MHC background did not seem to influence TCR gene usage in response to BI. The V beta 6+ clones appeared to be selected by the antigen. In contrast, no V beta 6+ clones could be isolated from (B6 x DBA/2)F1 mice, where V beta 6+ (and V beta 8.1+) T cells are deleted by self tolerance to Mls-1a. Thus, although a small proportion of residual V beta 6+ cells had been demonstrated in Mls-1a mice, these cells could not be retrieved in a response that uses V beta 6 predominantly. In functional terms, therefore, the deletion of V beta 6 by self tolerance appears to be complete. Instead of V beta 6, the majority (up to 60%) of I-Ab- as well as I-Ad-restricted insulin-specific clones from the (B6 x DBA/2)F1 mice expressed V beta 8.2 and V beta 8.3. This shift of gene usage was not accompanied by any detectable change in the fine specificity pattern of response. Thus, in the insulin-specific response, the flexibility of T cell repertoire fully compensates for deletions caused by self tolerance.