Figure 6. Methyldopa treatment reduces primary antigen–specific T cells restricted to HLA-DQ8 but not those presented by DR4.

Cryopreserved PBMCs were thawed, cultured in the presence or absence of protein/peptide for 48 hours, washed, and then transferred to an IFN-γ monoclonal antibody–coated plate for overnight culture, followed by development and enumeration of ELISPOTs. IFN-γ ELISPOT results from study subjects for (A) an insulin B chain mimotope, B:9-23 (B22E), known to be presented by DQ8, (B) whole tetanus toxin (TT) protein, (C) an epitope of TT consisting of amino acids 506-525 known to be presented by DR4, and (D) another DR4-restricted TT epitope, amino acids 922-941. Seven study subjects responded to the insulin B chain mimotope at baseline and were further evaluated for responses to TT protein and epitopes. Each data point represents the total number of spots for a given condition from triplicate wells, minus the total number of spots without antigen (background) for an individual. Symbols represent the same individual tested for each condition. *P = 0.016, by Wilcoxon matched-pairs, signed-rank test; P = NS for TT, TT_506-525, and TT_922-941. Supplemental Table 8 provides ELISPOT counts at baseline and 3 months for each individual and condition, including no antigen as a negative control and whole TT as a positive control.