Presentation of DM-sensitive antigens on primary hematopoietic and IFN-γ–treated nonhematopoietic cell types is regulated by HLA-DO. (A) Monocyte-derived immature (open bars) and mature (closed bars) dendritic cells (DCs) were generated from patient MRJ expressing all 5 antigens as well as their respective HLA class II restriction alleles, and recognition by the specific T-cell clones was tested by IFN-γ ELISA. Indicated is the T-cell recognition of mature versus immature DCs. (B) Primary fibroblasts expressing HLA-DRB3*0101 and DRB3*0202 with and without transduced HLA-DO were pulsed with recombinant MR1 (DM-sensitive) and PTK2B (DM-resistant) proteins, and recognition by the specific T-cell clones was tested without cytokine pretreatment or after 3-4 days of treatment with IFN-γ. Mean ± SD release of IFN-γ in duplicate wells is shown. The fibroblasts used for T-cell recognition were included in the microarray analysis as depicted in Figure 6B.