In a previous report (1), a family with C2 deficiency in the homozygous and the heterozygous states was described. The propositus was of special interest because the complete absence of C2 was associated with some manifestations of systemic lupus erythematosus. Further studies of this family included analysis of possible genetic linkage of the deficiency with known genetic markers. Determinations of HL-A antigens provided evidence that linkage with this system was present. Methods and MaterialsSerum samples were obtained from clotted blood, quickly frozen, and stored at -60°C. Samples were thawed once. C2 determinations were performed by both hemolytic titration and radial immunodiffusion (1). The heterozygous individuals were recognized by their level of C2 which was close to one half the normal.HL-A typing was done on lymphocytes isolated from the peripheral blood by Ficoll-Isopaque gradient centrifugation. A two-stage microtoxicity assay procedure was used. 120 typing sera were used and 28 antigens were typed for. The typing sera were obtained from the New York Blood Center and the Transplantation Immunology Branch Serum Bank of NIAID (2). Unidirectional mixed leukocyte cultures (MLC) were performed according to Hartzman et al. (3). Briefly, lymphocytes were isolated by Ficoll-Hypaque gradient centrifugation. 3 × 106 X-irradiated (3,000 rad) stimulating cells and 1.5 × 105 in 0.2 ml of RPMI 1640 medium supplemented with streptomycin, penicillin, and 20% heat-inactivated normal human serum were mixed in the wells of Falcon microtiter plates (Falcon Plastics, Div. of BioQuest, Oxnard, Calif.). Each culture was set up in triplicate. After 6 days of incubation at 37°C in 5% CO2 humidified atmosphere, 2 ~Ci of [SH]thymidine was added to each culture 16 h before harvesting. The lymphocytes were harvested and processed for liquid scintillation counting. Results and DiscussionThe pedigree of the S family is depicted in Fig. 1. The propositus, II2, is a woman with manifestations of systemic lupus erythematosus and homozygous for C2 deficiency. HL-A analysis also indicated homozygosity for HL-A10,W18. This was checked in two laboratories with different typing sera. To verify this further, unidirectional MLC were carried out using her cells as the stimulator and those of her daughter as the responder. It was clear that her daughter's leukocytes did

Studies in estrogen metabolism were carried out in 2 males with systemic lupus erythematosus (SLE) who also had Klinefelter's syndrome. Although these studies revealed elevated levels of urinary estrogens in 1 patient, abnormalities of estradiol metabolism suggesting persistent estrogen stimulation were detected in both. This report notes an association between SLE and Klinefelter's syndrome and suggests that chronic estrogenic stimulation may be significant in the development of SLE in these 2 patients.A high female incidence is well recognized in a variety of human disorders involving immunologic aberrations including the connective tissue group. In systemic lupus erythematosus (SLE) the ma1e:female ratio is approximately 1 t o 9 (1). T of small male genitalia, gynecomastia, and lack of secondary sexual characteristics, i.e. Klinefelter's syndrome, is of special note (2-4). In the present report two additional cases of SLE associated with Klinefelter's syndrome are noted. In addition, data are presented suggesting that these 2 patients have been under chronic estrogenic stimulation. MATERIALS AND METHODSAt the time of study neither patient was receiving corticosteroids or any sex hormone. Neither had ever taken immunosuppressive drugs other than corticosteroids. Urinary estrogens were measured by radioimrnunoassay frop 24-hour urine collections. Following hydrolysis with 8-glucuronidase and estrogen extraction, 24-hour urinary estrogens were measured by radioimmunoassay with specific antisera for estrone, estradiol, and estriol. Values for 20 normal males for estrone, estradiol, and estriol were determined (Table 1) ( 5 ) . Because urinary estrogen levels in Klinefelter's syndrome are frequently within the normal range (6,7), the metabolism of trace labeled estradiol was also studied in these patients.Estradiol 6-7-*H was injected intravenously (8) and urine was collected over 3 days. The recovery of total radioactivity in the glucosiduronate and nonglucosiduronate fractions of the urine was measured as previously described (8). In brief, a sample of the combined 3-day collection was treated with 8-glucuronidase and this glucosiduronate fraction was extracted with ether. The remaining activity was considered the nonglucosiduronate fraction. The pattern of radioactivity in the glucosiduronate fraction, the major urinary fraction, as various estrogen metabolites-estradiol (E2), estrone (El), estrio1 (E3). 2 methoxy El, and 2-OH El-was also determined (8).