Regulation of gene expression of murine MD-1 regulates subsequent T cell activation and cytokine production

The immunoadhesin (OX2:Fc) comprising the extracellular domain of murine OX 2 linked to IgG2aFc, inhibits production of IL-2 and IFN-gamma by activated T cells and increases allograft and xenograft survival in vivo. Increased expression of OX2 on dendritic cells (DC) in vivo following preimmunization via the portal vein is also associated with elevated expression of MD-1, W e have used antisense oligodeoxynucleotides (ODNs) to MD-1 to investigate t he effect of inhibition of expression of MD-1 by DC on their function as al lostimulatory cells. We also investigated by FAGS analysis the cell surface expression of OX2, CD80, and CD86 on DC incubated with ODN-1 blocking MD-1 expression. Blocking MD-I gene expression inhibits surface expression of C D80 and CD86, but not of OX2, DC incubated with ODN-1 to MD-1 did not stimu late IL-2 or IFN-gamma production, but generated cells able to suppress, in a second culture of fresh DC plus allogeneic T cells, production of IL-2 a nd IFN-gamma. This inhibition was blocked by anti-OX2 mAb, Infusion of DC p reincubated with ODN-1 prolonged renal allograft survival, an effect also r eversed by anti-OX2 mAb, By FAGS, incubation of DC with anti-MD-l Ab to pro mote capping eliminated cell surface expression of MD-1 and CD14 without al tering DEC205, DC26, CD80, CD86, or OX2 expression. Thus OX2 and MD-1 are i ndependent surface molecules on DC that may reciprocally regulate T cell st imulation. MD-1 is linked to CD14, a "danger receptor complex," and activat ion of this complex can regulate cell surface expression of CD80/CD86, whic h signal T cells.