OT-II/CD28Y170F T cells display normal antigen-driven expansion but defective localization to antigenic sites following priming in vivo. (A-B) CFSE-labeled OT-II and OT-II/Y170F CD4⁺ T cells detected in draining (mesenteric) lymph nodes after immunization with OVA_323-339 peptide and LPS (cells are gated based on CD4 expression). (C-D) Localization of CFSE-labeled T cells 96 hours after immunization in the peritoneal membrane of mice that received an intraperitoneal injection of LPS and IFNγ only (No Ag) or that had been also injected with OVA_323-339 peptide 48 hours later (+ Ag; scale bar: 40 μm). Panel D represents data averaged from at least 3 animals, and standard error bars are shown. *P < .03.