Lymphocyte and complement abnormalities in splenectomized patients with hematologic disorders.

Twenty-two patients, splenectomized 1 to 26 years earlier for hematologic disorders, were studied to determine possible defects in immunologic function or complement levels. Quantitation of B cells and T-cell subsets revealed slight decreases in the proportions of CD3 and CD4 cells but normal or increased absolute numbers of all cell populations. IgM synthesis in vitro by peripheral blood mononuclear cells was markedly diminished, but IgG synthesis was normal. Fractionation studies, in which various B-cell- and T-cell-enriched populations from controls and patients were combined, demonstrated diminished B-cell function in the patients. Sickle cell patients, who were functionally asplenic, showed similar deficits. Complement levels in splenectomized and sickle cell patients in both the classical and alternative pathways were generally normal. A modest decrease in component H in the alternative pathway in splenectomized and sickle cell patients probably was not clinically significant. In summary, splenectomized patients have a diminished capacity for IgM synthesis that can be attributed primarily to defective B-cell function. This may be partially responsible for their increased susceptibility to infection by encapsulated organisms.