Diminished CD40L expression on T-cells in a case of disseminated cryptococcosis.

X-linked hyperimmunoglobulin M (HIGM) syndrome may increase the susceptibility of patients to disseminated cryptococcal infections primarily due to CD40L deficiency that causes defective cross talk between T- and B-cells, thus preventing class switching. In HIGM syndrome, serum IgM levels are elevated with severe reduction in serum immunoglobulin G (IgG) and IgA levels. In addition, the expression of CD40L (CD154) on in vitro-activated T-cells is severely reduced or absent.