Genetic deficiency of C4 presenting with recurrent infections and a SLE-like disease. Genetic and immunologic studies.

A young girl presenting with recurrent pulmonary infections and atypical lupus erythematosus was totally deficient in C4. In one sister, also deficient in C4, the same symptoms developed. Results of family studies were consistent with an autosomal recessive mode of transmission and with linkage of the genes determining C4 deficiency to those of the major histocompatibility complex. The patient's serum and red cells were Chido- and Rodgers-negative. Humoral and cellular immunity were normal, except for a low lymphocyte response in mixed lymphocyte culture. The cellular function of the patient's polymorphonuclear leukocytes was normal, for both phagocytosis and bactericidal activity using Candida albicans. However, in the presence of C4-deficient serum, opsonin generation and bactericidal indexes were diminished. These defects were completely reversible upon addition of purified C4.