Objective: To investigate the expression of paired immunoglobin-like receptor B (PIR-B) on dendritic cells (DCs) and its relationship with tolerogenic DCs (T-DCs) in mouse.
Methods: DC2.4 cells, an immature dendritic cell line derived from C57BL/6 mouse, were stimulated by lipopolysaccharide (LPS) for 48 h to induce the mature dendritic cells (mDC) and cultured respectively with the recombined mouse interleukin-10 (rmIL-10) or recombined human transforming growth factor beta1 (rhTGF-beta1) to develop the tolerogenic dendritic cells (T-DC). Special small interference RNA (siRNA) molecular of PIR-B was chemically synthesized and transfected into DC2.4 cells (si-DC) by lip2000. The expression of PIR-B on DC2.4 cells was measured by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) and Western blot. The allogeneic lymphocyte proliferative capacity of DCs was measured by mixed lymphocyte reaction (MLR) using 3H-thymidine incorporation test. The concentration of IFN-gamma in supernatants of MLR was analyzed by ELISA.
Results: Semi-quantitative RT-PCR and Western blot showed that PIR-B mRNA and protein were expressed on DC2.4 cells. RmIL-10 and rhTGF-beta1 induced the higher PIR-B mRNA and protein level on T-DCs (Relative values were 0.51 +/- 0.08 and 0.58 +/- 0.23; 0.85 +/- 0.07 and 0.87 +/- 0.14; 0.79 +/- 0.10 and 0.85 +/- 0.34, respectively) (P < 0.05). LPS down-regulated the PIR-B expression on mDC (0.35 +/- 0.10 and 0.32 +/- 0.04) (P < 0.05). The PIR-B mRNA and protein expression were inhibited by siRNA transfection (decreased by 78.9% and 74.2% respectively after 48 h interference) (P < 0.05). DC2.4 cells stimulated the proliferation of BALB/c mouse allo-genetic spleen cell. The mDC enhanced alloreactivity in MLR and the IFN-gamma secretion in supernatants. The T-DCs alleviated the allo-genetic spleen cell proliferation (P < 0.05) and IFN-gamma secretion in MLR (P < 0.05). Silence of the PIR-B expression (si-DC) also promoted of alloreactivity and enhanced the IFN-gamma secretion in MLR (P < 0.05).
Conclusion: High expression of immune inhibition receptor PIR-B is one of the general features and molecular mechanism of dendritic cells to acquire immune tolerance in mouse.