Relationship between reduced B cell susceptibility to IgM antibodies and reduced IgD-bearing B cells in patients with systemic lupus erythematosus.

Peripheral blood lymphocytes from 14 patients with systemic lupus erythematosus, 5 patients with rheumatoid arthritis, and 10 normal subjects were cultured for 7 days with or without anti-IgM or anti-IgD antibodies, and IgG- and IgM-secreting cells were assayed by reverse hemolytic plaque assay. Surface immunoglobulin (Ig) isotypes on peripheral blood B cells were also examined by a direct anti-Ig rosetting reaction. In normal subjects and rheumatoid arthritis patients, the spontaneous development of IgG- and IgM-secreting cells was markedly suppressed by anti-IgM or anti-IgD antibodies. Over 50% of peripheral blood B cells were IgD- and IgM-bearing cells in normal subjects and in most patients with rheumatoid arthritis. In lupus patients, however, the suppression of IgG and IgM production by anti-IgM or anti-IgD antibodies was remarkably reduced, especially in the active stage. Furthermore, the percentage of IgD-bearing cells in peripheral blood B cells was remarkably reduced, especially in patients with active disease. There was a good correlation between reduced susceptibility of B cells to anti-IgM antibody-mediated suppression and reduced percentage of IgD-bearing cells in lupus patients.