The Role of the LAT–PLC-γ1 Interaction in T Regulatory Cell Function

Abstract

The interaction between the linker for activation of T cells (LAT) with PLC-γ1 is important for TCR-mediated Ca2+ signaling and MAPK activation. Knock-in mice harboring a mutation at the PLC-γ1 binding site (Y136) of LAT develop a severe lymphoproliferative syndrome. These mice have defective thymic development and selection and lack natural regulatory T cells, implicating a breakdown of both central and peripheral tolerance. To bypass this developmental defect, we developed a conditional knock-in line in which only LATY136F is expressed in mature T cells after deletion of the wild type LAT allele. Analysis of LATY136F T cells indicated that the interaction between LAT and PLC-γ1 plays an important role in TCR-mediated signaling, proliferation, and IL-2 production. Furthermore, the deletion of LAT induced development of the lymphoproliferative syndrome in these mice. Although Foxp3+ natural Treg cells were present in these mice after deletion, they were unable to suppress the proliferation of conventional T cells. Our data indicate that the binding of LAT to PLC-γ1 is essential for the suppressive function of CD4+CD25+ regulatory T cells.