Interleukin-10 does not affect phagocytosis of particulate antigen by bonemarrow-derived dendritic cells but does impair antigen presentation

Dendritic cells (DC) are important initiators of an immune response so unde rstanding the factors controlling antigen acquisition and presentation has important consequences for the use of these cells in vaccines and other for ms of immunotherapy. We investigated the factors that influence phagocytosi s by immature bone marrow-derived DC (BMDC) and the effect of interleukin-1 0 (IL-10) on this process. Two sizes of fluorescent particles and recombina nt bacillus Calmette-Guerin expressing the green fluorescent protein (rBCG) were used as particulate antigens. The percentage of cells taking up the a ntigen was found to be dependent on the size and dose of the particles, and the length of exposure to them. BMDC exposed to IL-10 at various concentra tions for different periods exhibited no distinguishable change in antigen uptake. However, if BMDC treated with IL-10 and rBCG were then exposed to a second dose of particulate antigen, uptake was increased compared with tho se BMDC not treated with IL-10. The expression of major histocompatibility complex class II, CD80, CD86 and CD11c by BMDC after phagocytosing rBCG or inert beads, was inhibited when the BMDC were pretreated with IL-10. In con trast, the expression of CD25 was increased. BMDC that had taken up BCG or purified protein derivative (PPD) were able to stimulate primed T-cell prol iferation but this was severely inhibited if the BMDC were cultured with IL -10 before exposure to the antigen. This work suggests that although IL-10 does not affect the phagocytic capacity of BMDC, it does inhibit maturation of the cells and consequently, T-cell activation.