CD4 and CD8 in T cell lineage commitment: alterations induced by expression of a CD8/CD4 chimeric transgene

The mechanism by which thymocytes expressing both the CD4 and CD8-coreceptor proteins differentiate into mature T cells expressing either CD4 or CD8 is not well understood. We have shown that expression of a chimeric CD8/CD4 transgene can alter T cell lineage commitment such that cells expressing a transgenic class I major histocompatibility complex-restricted T cell receptor can differentiate to the CD4 rather than those the CD8 lineage. The implications of these findings and those of others for existing instructive and stochastic models of thymocyte lineage commitment are discussed, and an alternative model is considered.