Influence of Bacterial Antigens On Activation of Human Splenic Dendritic Cells

The dendritic cells (DC) play crucial role in initiation and modulation of immune response especially innate immune response. Toll like receptors (TLR) on DC are receptors involved in innate immunity and recognizing conserved bacterial antigens like LPS and bacterial DNA. TLRs can also respond to some endogenous ligands (heat-shock proteins, heparan sulfate, fibrinogen and the contest of necrotic cells). Recognition of such endogenous substances would be a critical step in response to viruses, tumors and possibly to transplants. We investigated the influence bacterial antigens on splenic cell population enriched in DCs. After incubation with bacterial antigens the percentage of DC expressing HLA-DR+ and CD123+ cells increased whereas that of CD68+ and CD14+ decreased. In the untreated population of human splenic DC minimal expression of TLR2, TLR3 and CD123 was found, while other receptors were not detected. After incubation with bacteria a marked increase of CD83, TLR2, TLR3 and TLR4 was observed. Treatment with LPS increased expression of TLR2, TLR4, Hsp60 and Hsp90. Stimulation by bacterial DNA resulted mainly in Hsp60 and TLR9 expression. These observation may throw light on the mechanism of exacerbation of the rejection of transplanted organs by microbial stimulation.

Keywords: Dendritic Cells, Bacterial Antigens, innate immunity, Tlrs