CD28 and common variable immunodeficiency: This is the first study examining migratory function of granulocytes, oxidative burst activity of phagocytic cells, surface integrin expressions on neutrophils and lymphocytes, NK cell numbers and cytotoxic activity, NKT cell numbers, and lymphocyte subsets such as CD8+CD28+, CD4+CTLA-4+ cells in the same CVID patient group.