Hyper IgM syndrome associated with defective CD40-mediated B cell activation.

Recent studies show that most patients with X-linked hyper IgM syndrome have defects in the gene for CD40 ligand. We evaluated 17 unrelated males suspected of having X-linked hyper IgM syndrome. Activated T cells from 13 of the 17 patients failed to bind a soluble CD40 construct. In these patients, the sequence of CD40 ligand demonstrated mutations. By contrast, T cells from the remaining four patients exhibited normal binding to the CD40 …