Dendritic cell-mediated stimulation of the in vitro lymphocyte response to Aspergillus

Lymphocytes play a major role in host defense against Aspergillus, but little is known about the contribution of dendritic cells (DC) to antifungal immunity in humans. We have observed that DC derived from normal volunteers phagocytose heat-killed A. fumigatus conidia. Following 24 h of exposure to the fungus, DC displayed an increase in the mean fluorescence intensity of HLA-DR, CD80, and CD86, and an increase in the percentage of CD54(+) cells. These DC also displayed increased production of IL-12. DC derived from CD34(+) progenitors or monocytes stimulated autologous lymphocytes to proliferate and produce high levels of interferon-gamma, but not interleukin-10, in response to fungal antigen. DC generated from CD34(+) progenitors collected prior to autologous or allogeneic stem cell transplantation also partially restored the in vitro antifungal proliferative response of lymphocytes obtained from patients 1 month after transplantation. These results suggest that DC are important to host-response to A. fumigatus, and that ex vivo-generated DC might be useful in restoring or enhancing the antifungal immunity after hematopoietic stem cell transplantation.