DcR3 down-regulates MHC-II expression in vivo. (A) Serum levels of DcR3 in DcR3-transgenic mice. The concentrations of DcR3 in the sera of DcR3-transgenic mice and controls were determined by ELISA. P value of the coupled differences, compared with controls, was determined using the Student t test: **P < .01. (B,C) Expression of MHC-I and MHC-II in TAMs from DcR3-transgenic mice. CT26 tumor masses were removed from DcR3-transgenic mice or nontransgenic littermates. The expression of I-A^d (B) and H-2D^d (C) by TAMs (ie, CD11b⁺ cells stained in red) was determined by confocal microscopy (magnification 10 × 63).