Human blood dendritic cells express a phagocytically active form of the type-1 fey receptor (CD64)
Three types of FCï receptors for IgG, FcyRI (CD64), Fc-yRII (CD32), and FcyRIII (CD16), are expressed differentially on blood leukocytes. In particular, the high affinity CD64 is constitutively expressed on mature mononuclear phagocytes of the human myeloid system. Dendritic cells (DC), in contrast, have been reported to express CD32 but not CD64. We now demonstrate that CD64 is expressed on at least one subset of blood DC. Countercurrent elutriation was used to rapidly enrich a subset of blood DC (CD33briCD14neg9HLA-DRbriCD83neg) and monocytes (CD33briCD14>iHLADRdlmCD83>9). Upon culture for two days, blood DC became CD83-positive and markedly increased HLA-DR expression, whereas monocytes did not express CD83 and exhibited reduced levels of HLA-DR. Constitutive CD64 expression was identified on this circulating DC population, but at a lower level than on monocytes. Neither DC nor monocytes demonstrated any decrease in CD64 expression following 2 days in culture. Moreover, CD64 expression on DC was upregulated following incubation with interferon-v (IFN-y), and CD64 on both freshly isolated and cultured blood DC mediated phagocytosis, although at a lower level than that of monocytes. These results indicate that both CD64 and CD32 may play a role in uptake of foreign particles and macromolecules by blood DC prior to trafficking to T cell reactive areas of the spleen.
Fanger, NA; Wardwell, K; Shen, L; Tedder, TF; Guyre, PM
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