[Study on quantity and function of bone marrow macrophages in patients with BMMNC-Coombs Test(+) pancytopenia]

To explore the quantity and function of bone marrow (BM) macrophages in patients with BMMNC-Coombs Test(+) pancytopenia (BCTP).

Sixty-one patients with BCTP, 10 with severe aplastic anemia (SAA) and 13 normal controls were enrolled in this study. The quantity of BM macrophages was measured by FACS and their function was evaluated by phagocytosis test.

The number of macrophages, phagocytosis ratio and index of cock's red blood cells (CRBC) in BCTP patients were (0.57 +/- 0.30)%, (37.56 +/- 15.20)%, and 0.75 +/- 0.34, respectively, being significantly higher than those in SAA group \[0.46 +/- 0.08)%, (28.26 +/- 10.46)%, and in 0.59 +/- 0.39\] and in normal control \[0.44 +/- 0.69)% (25.63 +/- 14.75)%, and 0.55 +/- 0.16\] (P < 0.05). The BCTP patients were classified into two subgroups according to the quantity of macrophages: Group A (M(Phi) > or = 0.5%, 34 cases) and Group B (M(Phi) < 0.5%, 27 cases). There were 32 cases (94.12%) with BMMNC-IgG(+) in Group A and only 2 cases (7.41%) in Group B. There were significant differences in phagocytosis ratio and index of macrophages between Group A \[46.62 +/- 13.38)% and 0.91 +/- 0.36\] and Group B \[(28.67 +/- 12.59)% and 0.61 +/- 0.30\] (P < 0.05), while no statistical differences between group B and other two control groups (P > 0.05). Thirty-four BMMNC-IgG(+) patients were further divided into two subgroups: High level (HL) group \[> or = 0.75%, 9 cases (26.47%)\] and Low level (LL) group \[< 0.75%, 25 cases (73.53%)\]. Only one lineage of BMMNC-IgG could be detected in LL group. Among 9 patients in HL group, 8(23.53%) had two lineages of BMMNC-IgG and 1(2.94%) had three lineages. Phagocytosis ratio and index of macrophages were significantly higher in HL group \[(60.22 +/- 12.51)% and 1.23 +/- 0.23\] than in LL group \[(43.32 +/- 9.24)% and 0.84 +/- 0.24\] (P < 0.05). The level of peripheral blood(PB) RBC, HGB and PLT in HL group were significantly lower than in LL group (P < 0.05), while the percentage of Ret, the level of TBIL and the ratio of erythroid of sternal BM in HL group were significantly higher than in LL group (P < 0.05).

More quantity and stronger function of macrophages are observed in BCTP patients with BMMNC-IgG(+). One of the mechanism of hematocytopenia might be that macrophages activated by IgG autoantibodies phagocytose hematopoietic cells in BM. Macrophages do not involve in damage process of BM in BCTP with IgM or cold autoantibodies.