FIG. 4.

PhoP influences antigen-processing efficiency for MHC-II presentation when quantitated 2 h following Salmonella infection of DC. DC were infected with either phoP or phoP^c serovar Typhimurium expressing Crl-OVA or with phoP^c serovar Typhimurium expressing Crl-HEL (irrelevant epitope). After 2 h, the cells were washed and fixed, and either OT4H (A and C) or CD8OVA (B and D) T-hybridoma cells were added. (A) The OVA(265-277)I-A^b-specific OT4H T-hybridoma response to DC coincubated with viable phoP or phoP^c Salmonella expressing Crl-OVA or wild-type bacteria expressing Crl-HEL (irrelevant epitope) is shown. The amount of Crl-OVA expressed in the phoP^c Salmonella, relative to the amount expressed in the phoP Salmonella as determined by ELISA, is shown within parentheses. (B) The OVA(257-264)/K^b-specific CD8OVA T-hybridoma response to DC coincubated with viable phoP or phoP^c Salmonella expressing Crl-OVA or wild-type Salmonella expressing Crl-HEL (irrelevant epitope) is shown. (C) The OT4H T-hybridoma response to DC coincubated with 10⁷ viable phoP or viable phoP^c or heat-killed phoP^c Salmonella expressing Crl-OVA is shown. (D) The CD8OVA T-hybridoma response to DC coincubated with 10⁷ viable phoP or viable phoP^c or heat-killed phoP^c Salmonella expressing Crl-OVA is shown. Rough-LPS Salmonella strains were used in these experiments. Data are presented as the means of triplicate samples ± 1 standard deviation. Similar results were obtained in at least three independent experiments.