CD40LG and common variable immunodeficiency: According to the European Society for Immunodeficiencies (ESID)/Pan-American Group for Immunodeficiency (PAGID), the definition of CVID was as follows: patient with a markedly reduced serum levels of immunoglobulin (Ig)G, in combination with low levels of IgA and/or IgM, and meeting the following criteria: (1) the onset of immunodeficiency at more than 2 years of age; (2) insufficient or absent response to immunizations of vaccines; and (3) exclusion of other defined immunodeficiency states (2, 3).