CD79A and immunodeficiency disease: Currently, the Pan-American Group for Immunodeficiency (PAGID) and the European Society for Immunodeficiencies (ESID) define probable CVID as “serum IgG and IgA at least two SDs below the mean with the following criteria: (1) onset of immunodeficiency at >2 years of age; (2) absent isohemagglutinins and/or poor response to vaccines; (3) defined causes of hypogammaglobulinemia have been excluded” (10).