FIGURE 6.

Thymocytes, macrophages, and DCs express endogenous MR1 and activate MAIT cell hybridomas in the presence of the enhancing mAb. Thymocytes from wild-type (WT) and MR1 KO mice were used as APCs in the coculture with the MAIT cell hybridoma 6C2 in the absence or presence of anti-MR1 mAb 8H9.D11. A, The IL-2 production of 6C2 was measured by ELISA. The plot represents data from one of three independent experiments that were performed using one mouse for each genotype and set up in triplicate. B, Thymocytes were stained for surface expression of CD4 and CD8, followed by intracellular staining of mAb 8F2.F9 for MR1. In the graph (left panel), the blue line indicates the staining in WT thymocytes; the black line indicates the background in MR1 KO thymocytes. Right panel, MR1⁺ WT thymocytes were mostly CD4⁺CD8⁺. FACS analysis represents staining results of one mouse for each genotype in one representative experiment. C, Total cells (RBCs lysed), macrophages, and DCs from the spleen of WT mice were used as APCs to activate 6C2 in the presence of mAb 8H9.D11 using the same method described in A.