Spontaneous production of bone-resorbing lymphokines by B cells in patients with systemic lupus erythematosus

The culture supernatant of B cells from patients with active systemic lupus erythematosus (SLE) who had never been treated with corticosteroids had bone-resorbing activity (BRA) which stimulated the 45Ca release from prelabeled murine fetal bones. Then we studied the characteristics and the relationship of this BRA with several lymphokines previously reported. The BRA was eluted as three peaks at approximately 17,000, 35,000, and 80,000 daltons by Sephacryl S-200 column chromatography. Recombinant (r)IL 1 alpha, rIL 1 beta, and rTNF possessed BRA, but rIL 4 and rIL 6 did not. Furthermore, the BRA from SLE B cells was absorbed with anti-IL 1 alpha antibody but not with anti-IL 1 beta and anti-TNF antibody. Therefore, the fact that SLE B cells produce BRA which corresponds to IL 1 alpha and IL 1 alpha produced by B cells might be one of the causes of bone destruction in SLE patients.