Culture and Comparison of Feline Myeloid Dendritic Cells vs Macrophages

To gain insight into the role of dendritic cells (DCs) in feline immunodeficiency virus (FIV) infection and immunity, methods were developed to culture feline myeloid DCs from CD14+ monocytes with a combination of human recombinant granulocyte-macrophage colony-stimulating factor (hrGM-CSF) and interleukin-4 (hrIL-4). These cells were compared with feline macrophages cultured in the presence of hrGM-CSF. As with DCs in other species, feline DCs showed uniformly high MHC class II expression, moderate B7.1 expression, potent induction of the allogeneic mixed leucocyte reaction (MLR), and moderate uptake of fluorescein isothiocyanate-dextran (FITC-DX) in the endocytic assay. In comparison with feline macrophages, DCs showed higher expression of MHC class II, similar expression of B7.1, CD14, CXCR4 and CD1a, and lower expression of CD11b. When placed on alcian blue-coated glass slides, DCs differed from macrophages in showing a greater tendency to spread out; they also had characteristic fine cytoplasmic processes instead of the broader pseudopodia of macrophages. Basal IL-12 mRNA expression and FITC-DX uptake were greater in DCs than in macrophages. Unlike feline DCs, feline macrophages exhibited a dose-dependent suppressive effect in the MLR. Feline DCs propagated in vitro should prove useful in the development of DC-mediated vaccination and therapy for infectious and neoplastic feline diseases. Additionally, macrophages cultured with GM-CSF provide a potential means of studying the mechanism of immunosuppression in cats.