Violation of allelic exclusion of the T cell receptor beta genes in a helper T cell clone.

The 4-hydroxy-3-nitrophenylacetyl coupled to chicken gamma globulin specific and I-Ab restricted helper T cell clone IH4 carries a V beta 8.1-D beta 2.1-J beta 2.3-rearrangement on one and a V beta 16-D beta 2.1-J beta 2.5-rearrangement on the other chromosome. Both rearranged beta genes are transcribed and the products of both genes are expressed on the cell surface. This result implicates the absence of allelic exclusion of the T cell receptor beta genes in this T cell clone. The finding of a pseudoleader 5' to the functional leader exon of the V beta 16 gene suggests that this gene is not efficiently translated and that the amount of V beta 16 chains synthesized is not sufficient to activate the inhibitory mechanism preventing a second V beta to D beta J beta rearrangement.