Role of dendritic cells in the immune response to T-independent antigens of type 2

Dendritic cells (DC) belong to the most effective antigen-presenting cells. Their role in the presentation of thymus-dependent antigens and initiation of primary immune response is well known. At the same time, participation of DC in the immune response to T-independent antigens of type 2 (TI-2 antigens) is poorly explored. In this work, the ability of DC to initiate the immune response to a TI-2 antigen α(1→3) dextran (Dex) is investigated. Mouse bone-marrow-derived DC were generated by culturing the precursors with GM-CSF and then DC were pulsed by TI-2 antigens. The pulse induced DC activation, as was verified by an increase in the number of CD80 and CD86 positive cells. Uptake of FITC-labeled Dex was examined by flow cytometry. At a concentration of FITC-Dex of 100 μg/106 cells, the number of DC binding the antigen (Ag) reached “plateau”. DC charged by TI-2 antigens were mixed with normal mouse splenocytes and cultivated in RPMI-1640 medium for 4 days. The numbers of antibody- and immunoglobulin-forming cells were determined by ELISPOT method. The mixtures of splenocytes and naive DC not charged by the Ag were used as control. It was shown that the increase in the numbers of AFC and IFC under the influence of naive DC did not exceed 20%. On the contrary, the addition of DC pulsed by the Ag increased specific immune response more than twofold. The data obtained point to the direct interactions of DC with TI-2 antigens. Pulsed DC present TI-2 antigens to mouse splenocytes and induce specific and polyclonal B-cell activation, i.e., possess immunostimulating activity.