CD40LG and common variable immunodeficiency: studied both humoral and cellular immune responses to influenza following trivalent vaccination in a small group of CVID and ‘unclassified antibody deficiency’ patients, and found that while only 1 of 8 CVID patients and 4 of 8 ‘unclassified antibody deficiency’ patients mounted a specific antibody response to influenza vaccination, most of the CVID (7/8) and ‘unclassified antibody deficiency’ (6/8) patients mounted a cellular immune response as measured by vaccine-induced T cells (the frequency of CD40L+ T cells producing interferon-γ, tumor necrosis factor-α, and interleukin-2) (55).