Heterogeneity of bone marrow-directed immune mechanisms in the pathogenesis of neutropenia of Felty's syndrome.

Twenty-seven patients with Felty's syndrome were studied by the colony forming unit in culture (CFU-C) assay for possible immune mechanisms within the bone marrow compartment that could contribute to the neutropenia. Depletion of bone marrow suppressor T cells resulted in normal CFU-C numbers in 7 patients. In 5 patients serum antiprecursor cell activity was detected. Blood monocytes failed to generate colony stimulating factor in 5 patients. Bone marrow-directed immune mechanisms are heterogeneous and could play a role in the pathogenesis of neutropenia in some patients with Felty's syndrome.