A Micropolymorphism Altering the Residue Triad 97/114/156 Determines the Relative Levels of Tapasin Independence and Distinct Peptide Profiles for HLA-A24 Allotypes

Figure 3

HLA-A24/156 variants are associated at similar levels with TAP and TPN. Lysates from HLA-A24 transduced 721.221 cells were immunoprecipitated with TAP1 (Figure 3(a)) or with PaSta-1 (anti-TPN) antibody (Figure 3(b)). The immunoprecipitates were subjected to SDS-PAGE and transferred to PVDF membranes that were probed with antibody against HLA-A heavy chain, CRT, ERp57, TPN, and TAP1. All the 3 HLA-A24/156 variants showed similar levels of association with TPN in 721.221 cells indicating that they make use of TPN when it is present (Figure 3(b)). HLA-A24/156 variants showed strong associations with TAP1 in 221 cells (Figure 3(a)). They were weakly associated with TAP1 in 220 cells lacking functional TPN. Lysate controls showed decreased steady state TAP1 levels in 220 cells compared to 221 cells (Figure 3(c)). Lysate controls showed similar levels of HLA-A24, CRT, and ERp57 in all the transduced 721.220 and 721.221 cells (Figure 3(c)) and similar levels of TPN in all the transduced 721.221 cells.

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