The presence of MHC-I ligand does not improve the responsiveness of NKG2⁺ CD8αα iIELs. MIP-1α production by iIELs from B6 (■) or H-2K^bD^b double-deficient () mice on in vitro stimulation with plate-bound anti-CD3 mAb was determined. MIP-1α production by the indicated MHC-I receptor⁺ CD8αα iIEL subpopulations is shown relative to CD8αα iIELs lacking inhibitory MHC-I receptors as mean ± SEM for H-2K^bD^b double-deficient (n = 5) and B6 mice (n = 12). The data on B6 iIELs are the same as those shown in Figure 2A. There were no significant differences (NS) in MIP-1α production between iIEL subpopulations from B6 and H-2K^bD^b double-deficient mice (Mann-Whitney).