Presence or absence of minor H antigen–specific regulatory T cells analyzed in the tvDTH assay. Total PBMCs of 2 mothers with male offspring were tested for minor H antigen HY-driven bystander suppression of recall responses. PBMCs were injected together with either a mixture of recall antigens comprising tetanus toxoid (TT) and diphtheria toxoid (D), minor H allopeptide HY (allo HY) or minor H self-peptide HA-2^V or HA-2^M (self HA-2^V, self-HA-2^M) alone or with a combination of TT/D + allo- or self-peptide into the footpads of CB17.SCID mice. Footpad swelling, indicated as net swelling on the y-axis, was measured 24 hours later. Percentages indicate the percentage of inhibition of the recall response (■) in the presence of allo- (▨) or self-(□) minor H peptide. Mother ♀4 (left graph) displays a tvDTH regulator phenotype; mother ♀7 (right graph) is classified as a tvDTH nonregulator.