OBJECTIVETo investigate the variation of bone marrow complement level in cytopenia patients with positive BMMNC-Coombs test (CBCPC), and probe the role of complement in destroying hematopoietic cells of CBCPC patients.

METHODSOne hundred and twenty-four patients with CBCPC and twenty-three healthy donors as controls were enrolled in this study. The levels of CH50, C3, C4, C5b-9 were tested with ELISA. The auto-antibodies on bone marrow hematopoietic cells (BMHC) were examined with flow cytometry.

RESULTSThe level of C5b-9 in bone marrow (BM) of untreated CBCPC patients [(119.8+/-54.0) microg/L] was significantly higher than that of recovered patients [(100.7+/-33.4) microg/L] or normal controls [(93.9+/-28.8) microg/L] (P<0.05). The levels of CH50 in BM of untreated or recovered CBCPC patients [(33.3+/-11.5) kU/L, (30.8+/-10.3) kU/L] were significantly higher than that of normal controls [(24.1+/-6.4) kU/L] (P<0.05). The level of C3 in BM of untreated or recovered CBCPC patients [(4.9+/-2.2) mg/L], (5.0+/-3.5) mg/L] was significantly lower than that of normal controls [(7.0+/-5.6) mg/L] (P<0.05). The level of complement in peripheral blood was consistent with that in BM. CH50 in BM of CBCPC patients was negatively correlated with their C3 (r=-0.303, P=.0007) and positively correlated with their C5b-9 (r=0.241, P=0.003) levels. The level of C5b-9 in BM of CBCPC patients was higher in the BMHC-IgM positive group [(117.6+/-55.7) microg/L] than in the BMHC- IgM negative group [(99.2+/-26.2) microg/L] (P<0.05). The positive rate of CD34(+)-IgG or CD34(+)-IgM of CBCPC patients was positively correlated with their C5b-9 level (r=0.593, P=0.000, r=0.326, P=0.049). The reticulocyte percentage (r=0.421, P=0.000) and serum indirect bilirubin level (r=0.230, P=0.032) of CBCPC patients were positively correlated with their CH50 level.

CONCLUSIONSThe hematocytopenia of CBCPC patients might be related to the hematopoietic cells destruction caused by auto-antibody activated complements.