Activation of splenic dendritic cells by bacterial and allogeneic antigens.

Allograft ischemia and cellular degradation accompanying rejection favor graft colonization by translocated microorganisms. Bacterial colonization adds to the graft destruction. The dendritic cells (DC) of allograft recipients engage in allogeneic and antibacterial reactions; they process and present to lymphocytes 2 types of antigens. This may lead to overstimulation of DCs that may nonspecifically intensify the rejection process. We investigated the effects of allogeneic and bacterial antigens on splenic DCs phenotypes. In vitro stimulation of a spleen DC-enriched population by E. coli, LPS, and CpG DNA brought about an increase in expression of OX6(+) (MHC class II) from 47.4% in the control cells to 65% in the E. coli-stimulated group (P < .05) and 85% in the LPS and CpGDNA groups (P < .05). Interestingly, a significant drop in the frequency of OX62(+) DC was observed after incubation with LPS. Allogeneic heart transplants brought about an increase of OX6(+) in DCs to 100% and a decrease of ED1(+) monocyte frequency. Simultaneously, an increase in expression of W3/13(+) T cells in DC-enriched splenic cells was observed. There was no significant change in the frequency of OX62(+) expression. Both types of antigens evoked splenic DC response; however, there were differences in the frequency of phenotype expression. Allogeneic but not bacterial antigens increased W3/13 antigen expression; the frequency of OX62(+) in cells decreased after LPS but not after bacterial stimulation.