T cell assays show the relative functional avidity of environmental ligands. (A-L) Unprimed splenocytes from previously described HLA-DR15 and TCR transgenics carrying an anti-MBP (85-99) specific TCR (clone Ob1.A12) on an HLA-DR1501/Aβo background (n = 6) were cultured in triplicate on precoated IFNγ ELISpot plates with 0.25, 2.5, or 25 μg/ml of each of the 12 test peptides, MPB 85-99, and a negative control peptide (HLA-DR1501 binding peptide from Burkholderia pseudomallei, AhpC, BPSL2096 (51-70) KDFTFVCPTEIVEFAKLAKQ which stimulates potent CD4 T cell responses in HLA-DR1501/Aβo transgenic mice ). Cells were cultured for 72 h before plate development. Data are expressed as SFC/106 splenocytes and shown as mean values ± SEM. In each case, MBP 85-99 positive control peptide is indicated as closed squares, test peptide as closed circles, and negative control peptide as closed triangles. Test peptide identities were as follows: (A) Encephalitozoon romaleae, FGVKIHFFKQRNSL; (B) Chlorobium chlorochromatii CaD3, VFGNVHFFKNTGSA; (C) Rhodococcus sp. AW25MO9, AAQRIHFFKNLSLL; (D) Clostridium papyrosolvens, LNKNIHFFKNLPLP; (E) Anoxybacillus flavithermus, RLSVVHFLRANAVS; (F) Macrophomina phaseolina MS6, AAQNVHFWKALNQL; (G) Emiliania huxleyi CCMP1516, STARVHFWRSRSSE; (H) Rhizobium leguminosarum, DVSKVHFFKGNGQT; (I) Runella slithyformis DSM 19594, HRAKLHFFKDENLK; (J) Dictyostelium fasciculatum, YKHKIHFFKNEVLE; (K) Ogataea parapolymorpha DL-1, IEAAIHFYKGLAVY; (L) Myxococcus stipitatus DSM14675, SSARLHFFRALPHP.