title: Repressed classical complement pathway activities and clinical correlations in chronic lymphocytic leukaemia.
abstract: Haemolytic activities of the classical and alternative complement pathways, and levels of C1, C4, C3, factor B and C1 inhibitor (C1-INH) were measured in 137 serum samples of 69 patients with chronic lymphocytic leukaemia (CLL). In most sera IgG, IgA and IgM concentrations were determined as well. Clinical correlations of these laboratory parameters have been studied. C1 and C4 activities were found to be depressed in almost 50% of the sera tested, and hypogammaglobulinaemia was observed with a similar frequency. Low C1 and C4 levels were found mainly in the early stages of the disease. A strong association between the occurrence of infections and hypogammaglobulinaemia was observed, although low immunoglobulin levels frequently occurred in patients without a history of infections. Low C1 and C4 levels were significantly correlated with the incidence of infections, too, and this correlation was observed mostly in the early stages of the disease. The reason for this is not known. The present results suggest that not only low immunoglobulin levels but low C1 and/or C4 levels may contribute to the increased susceptibility to infections in patients with chronic lymphocytic leukaemia.
mesh_terms: D003167:Complement Activation; D003172:Complement C1 / Q000032:analysis; D003181:Complement C4 / Q000032:analysis; D003171:Complement Pathway, Classical; D006801:Humans; D007136:Immunoglobulins / Q000032:analysis; D007945:Leukemia, Lymphoid / Q000188:drug therapy / Q000276:immunology*
chemical_list: D003172:Complement C1; D003181:Complement C4; D007136:Immunoglobulins