Monocytes constitute the only peripheral blood cell population showing an increased burst activity in multiple sclerosis patients.

We examined peripheral mononuclear cells (PMNC), peripheral polymorphonuclear cells (PPNC), adherent mononuclear cells, non-adherent mononuclear cells, non-phagocytic mononuclear cells and non-phagocytic Percoll-fractionated mononuclear cells of multiple sclerosis (MS) patients for their spontaneous burst activity (BA). According to previous results PMNC of MS patients showed a markedly increased BA (p = 0.0002); PPNC, however, did not show significantly elevated values (p = 0.36). Further separation of PMNC and identification of the cells obtained by FITC-conjugated antibodies, esterase and Giemsa staining revealed high mean coefficients of correlation (r) between the BA and the number of esterase-positive cells (MO; r = +0.97) and the number of surface Ig-positive cells (B cells; r = +0.97). r was negative for the correlation between the BA and OKT3-positive cells (T cells; r = -0.99) and for the correlation between the BA and the number of large granular lymphocytes (r = -0.39). As in the range below 2,000 counts/10 s r is -0.5 between the BA and the number of B lymphocytes, while r is +1.0 between the BA and MO, and there are BA values below 500 counts/10 s although around 10% B cells but no MO are present, the results suggest that MO are the only cell population responsible for the increased BA in MS patients. Based on recent findings in our laboratory the results additionally indicate that in the peripheral blood interferon-gamma stimulates the BA of MO only.