Key result
The frequency of IgM-RF producing B cells was 1/3100 in normal controls, while in 4 patients with seropositive rheumatoid arthritis it varied widely from 1/262 to 1/20000.
Observational (n=9)
The frequency of circulating IgM-RF producing B cells is highly variable in patients with seropositive rheumatoid arthritis compared to normal controls.
Variability in IgM-RF B-cell frequency among seropositive RA patients leaves open its biomarker potential; hypothesis-generating and should not yet change practice.
Recently, a new culture system has been devised which leads to activation, proliferation and differentiation into antibody secreting cells of at least 90% of human peripheral blood B-lymphocytes. The system uses mutant EL-4 thymoma cells of mouse origin for B cell activation and T cell/macrophage supernatant as source of cytokines (L. Wen et al., Eur. J. Immunol. 17, 887, 1987). By an ELISA system with Fc fragments as antigen and the F(ab)2 fragment of antibodies against human IgM labelled with alkaline phosphatase, we analysed the frequencies of B cells producing IgM-RFs. The mean frequency of IgM-RF producing cells in normal controls was 1/3100 (s.d. = 0.2 log; n = 5) of circulating B cells. In 2 patients with seropositive rheumatoid arthritis (RA) the frequencies were higher (1/492; 1/262), but in 2 other seropositive patients a normal (1/5540) or even a decreased (1/20000) frequency was observed. The possible relation between circulating and synovial RF producing B cells is currently being investigated.
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VISCHER et al. (1988) conducted an observational in Rheumatoid arthritis (n=9). Seropositive rheumatoid arthritis vs. Normal controls was evaluated on Frequency of IgM-RF producing cells. The frequency of IgM-RF producing B cells was 1/3100 in normal controls, while in 4 patients with seropositive rheumatoid arthritis it varied widely from 1/262 to 1/20000.
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