FIG. 4.
Effect of Yersinia-mediated hypertranslocation on MHC class II-restricted antigen display. Presentation of the CD4 T-cell epitope LLO190-201 was monitored in an in vitro antigen presentation assay. (A) APC were infected with Y. pseudotuberculosis pIB102 or pIB155 bearing the indicated plasmids which encode the secreted or translocated form of hybrid YopE/LLO. (B) The sensitivity of the LLO190-201-specific CD4 T-cell line was monitored after loading of APC with graded amounts of peptide. Activation of T cells was measured as the amount of IFN-γ secreted into the culture supernatant. The means and standard deviations of duplicate cultures are indicated. The dotted line at 0.05 ng/ml indicates the detection limit of the IFN-γ ELISA.