Altered CD40 ligand induction in tolerant T lymphocytes

CD40 ligand (CD40L) is a member of the tumor necrosis factor superfamily and is expressed on the surface of activated T lymphocytes. The interaction of CD40L with CD40 on B cells results in B cell activation, immunoglobulin (Ig) secretion and Ig class switching. To study anergy as a mechanism of murine CD4 T cell tolerance, we determined both in vivo and in vitro that CD3‐activated anergic cells are deficient in the ability to stimulate B cell proliferation, and that anergic cells are defective for the T cell receptor/CD3‐mediated induction of CD40L expression. These results have implications for the recruitment of B cell responses by anergic T cells in vivo.