Figure 3.

Defective tapasin expression is not inducible by IFN-γ, but can be restored by transfection. (a) The cell lines indicated were either untreated (−) or treated (+) with IFN-γ for 20–24 hr before lysis and analysed as in Fig. 2a. (b) M553 cells and transfectants containing R240tpsn or T240tpsn alleles were lysed and immunoprecipitated using tapasin-specific antibody (PaSta1) or control antibody. (c). Western blots were probed for tapasin using rabbit antiserum (R.SinB). (c) Lysates from M553 and M553(T240)tpsn cells were serially diluted and after SDS–PAGE, the indicated proteins were detected by immunoblot analysis. (d) M553 and M553(T240)tpsn cells were tested for TAP function as described in the Materials and methods. (e) Serial dilutions of untreated (-IFN-γ) M553 and M553(R240)tpsn cells were immunoblotted as indicated. (f) IFN-γ-treated M553 and M553(R240)tpsn cells were analysed as in (e). Quantification of the fluorescent bands in (e) and (f) was performed with ImageQuant software. Each bar represents the average of the TAP1 : tubulin signal over all dilutions. A representative figure from at least three independent experiments is shown.