Andre Veillette, MD, Montreal Clinical Research Institute

Dr. André Veillette has had a longstanding interest in elucidating the molecular mechanisms by which immune cells are regulated. In the past, he discovered that two important receptors expressed on T cells, CD4 and CD8, are physically associated with an intracellular enzyme known as the â??protein tyrosine kinaseâ? Lck. He and his team uncovered that Lck is implicated in the initiation of the activation of T cells by antigens. A similar role was demonstrated for Fyn, another protein tyrosine kinase present in T cells. Dr. Veillette's laboratory also found that Csk, a third protein tyrosine kinase, suppresses the activation of T cells, as a result of its capacity to inactivate Lck and Fyn. This function requires the association of Csk with PTPN22/Lyp/PEP, an enzyme referred to as a â?protein tyrosine phosphataseâ?. Mutations of PTPN22/Lyp/PEP that interfere with the ability to associate with Csk were shown to exist in humans with various types of auto-immune diseases including diabetes, rheumatoid arthritis and lupus.