Depressed CD40 Ligand Expression Contributes to Reduced Gamma Interferon Production in Human Tuberculosis

Expression of CD40 ligand (CD40L) correlated directly with Mycobacterium tuberculosis-stimulated gamma interferon (IFN-γ) production by peripheral blood mononuclear cells (PBMC) from tuberculosis patients and healthy tuberculin reactors. The CD40L agonist increased M. tuberculosis-induced IFN-γ production by PBMC, and anti-CD40 or anti-CD40L antibodies reduced IFN-γ production. CD40L expression on PBMC was reduced by exposure to B cells and to soluble factors from M. tuberculosis-infected monocytes. These findings suggest that CD40L dysregulation contributes to reduced IFN-γ production in human tuberculosis.