Rheumatoid arthritis complicated by mycobacterium tuberculosis are there characteristics predisposing to this association?

Several studies have reported that the emergence of mycobacterium tuberculosis (TB) is increasing, and that it may be a critical complication of rheumatoid arthritis (RA). Thus, we assessed the clinical and immune status of RA patients with TB to look for features that might favor infection. Seven RA patients with a history of TB and 62 RA patients without TB were compared in terms of background, RA disease activity, and the concentrations of serum soluble cell surface markers (sCD4, sCD8 and sCD23). There were no differences in RA activity between the two groups. It is noteworthy that the RA patients with TB had not been treated with immunosuppressives. Counts of lymphocytes, but not neutrophils, were significantly less in the RA patients with previous TB than in those without TB. The serum concentration of sCD23, a marker of B cell activation, was significantly higher in the RA with TB group. There was also a nonsignificant but considerable difference in the mean sCD8 concentration between the two groups. These results suggest that B cell and possibly also T cell activation is prominent in the RA patients with a history of TB, and that lymphocyte activation might explain in part the high susceptibility of RA patients to TB.