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We explored the ex vivo alteration in the cytokine release of stimulated blood taken from healthy volunteers treated subcutaneously with 480 micrograms granulocyte colony-stimulating factor (G-CSF). In a double-blind, controlled, randomized study with 21 volunteers who received G-CSF once or twice 24 hours apart, we measured lipopolysaccharide (LPS)-inducible release of various cytokines and soluble receptors at different times after treatment. At day 1 after a single dose of G-CSF, mediator release was also initiated with muramyl dipeptide, Staphylococcus aureus enterotoxin A, lipoteichoic acid, streptolysin O, complement factor C5a, phytohemagglutinin, or phorbol myristate acetate. In blood from G-CSF-treated subjects, our major findings were (1) a maximal 12-fold increase in interleukin-1 receptor antagonist (IL-1ra) release and an increase of both the p55 and p75 soluble tumor necrosis factor (TNF) receptors; (2) a reduction in TNF release when using all the various stimuli described except LPS; (3) an increase in G-CSF and, to lesser extent, in IL-6, IL-8, and IL-10 release; and (4) an attenuation of interferon-gamma (IFN-gamma) and granulocyte-macrophage (GM)-CSF release. Our findings demonstrate that the major effect of G-CSF treatment is a change in the responsiveness of blood towards a variety of stimuli, which we interpret as a shift toward an antiinflammatory cytokine response.

The expression of C5a receptors (C5aR) on human leukocytes was evaluated by flow cytometry using fluorescein-labeled human C5a (C5a- F). Granulocytes and CD14+ mononuclear cells (MNL) but not CD3+, CD20+, CD16+, CD56+, or CD11b+ lymphocytes in peripheral blood and spleen bound C5a-F. C5a-F binding was saturable and inhibitable by anti-C5a monoclonal antibody (MoAb) C17/5 or unlabeled C5a. During hemodialysis, which led to the generation of C5a, only granulocytes and monocytes increased their expression of the adhesion molecule CD11b (CR3). In vitro, C5a induced an increase of CR3 and p 150/95 (CD11c/CR4) only on myeloid cells. However, treatment of leukocytes with phorbol 12- myristate 13 acetate increased CR3 and CR4 expression on both myeloid cells and a lymphocyte subpopulation. Stimulation of MNL in mixed lymphocyte cultures or by treatment with conditioned medium or with IFN- gamma did not induce binding sites for C5aR on lymphocytes and reduced the binding of C5a-F to monocytes. The expression of C5aR on low- density bone marrow cells was analyzed by setting appropriate gates during flow cytometry. Cells that bound C5a-F were found in all populations that contained granulocyte and monocyte precursors, but not in lymphocyte precursor populations. All C5aR+ bone marrow cells were CD34 and expressed high levels of CR3, which suggests a late appearance of C5aR during myeloid cell maturation. Our results indicate that C5aR is exclusively expressed on myeloid cells within the hematopoetic cell population.

The expression of C5a receptors (C5aR) on human leukocytes was evaluated by flow cytometry using fluorescein-labeled human C5a (C5a- F). Granulocytes and CD14+ mononuclear cells (MNL) but not CD3+, CD20+, CD16+, CD56+, or CD11b+ lymphocytes in peripheral blood and spleen bound C5a-F. C5a-F binding was saturable and inhibitable by anti-C5a monoclonal antibody (MoAb) C17/5 or unlabeled C5a. During hemodialysis, which led to the generation of C5a, only granulocytes and monocytes increased their expression of the adhesion molecule CD11b (CR3). In vitro, C5a induced an increase of CR3 and p 150/95 (CD11c/CR4) only on myeloid cells. However, treatment of leukocytes with phorbol 12- myristate 13 acetate increased CR3 and CR4 expression on both myeloid cells and a lymphocyte subpopulation. Stimulation of MNL in mixed lymphocyte cultures or by treatment with conditioned medium or with IFN- gamma did not induce binding sites for C5aR on lymphocytes and reduced the binding of C5a-F to monocytes. The expression of C5aR on low- density bone marrow cells was analyzed by setting appropriate gates during flow cytometry. Cells that bound C5a-F were found in all populations that contained granulocyte and monocyte precursors, but not in lymphocyte precursor populations. All C5aR+ bone marrow cells were CD34 and expressed high levels of CR3, which suggests a late appearance of C5aR during myeloid cell maturation. Our results indicate that C5aR is exclusively expressed on myeloid cells within the hematopoetic cell population.

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