Unexpected Role for the B Cell-Specific Src Family Kinase B Lymphoid Kinase in the Development of IL-17-Producing γδ T Cells

The Ag receptors on alpha beta and gamma delta T cells differ not only in the nature of the ligands that they recognize but also in their signaling potential. We hypothesized that the differences in alpha beta- and gamma delta TCR signal transduction were due to differences in the intracellular signaling pathways coupled to these two TCRs. To investigate this, we used transcriptional profiling to identify genes encoding signaling molecules that are differentially expressed in mature alpha beta and gamma delta T cell populations. Unexpectedly, we found that B lymphoid kinase (Blk), a Src family kinase expressed primarily in B cells, is expressed in gamma delta T cells but not in alpha beta T cells. Analysis of Blk-deficient mice revealed that Blk is required for the development of IL-17-producing gamma delta T cells. Furthermore, Blk is expressed in lymphoid precursors and, in this capacity, plays a role in regulating thymus cellularity during ontogeny. The Journal of Immunology, 2010, 185: 6518-6527.