Ex-vivo T cell recall responses to Ovalbumin are equivalent in DPP IV null and wild type animals. Wild type (open square) and DPP IV KO (filled square) animals (n = 3) were immunized with Ova in alum and draining mesenteric lymph nodes were harvested on day 9. Cells were than re-stimulated with various concentrations of Ova in vitro and a) proliferation and b) IL-2 production measured by [3H] thymidine incorporation and ELISA respectively as described in Methods and Materials. Wild type and DPP-IV KO unstimulated cell proliferation was 843 ± 244 and 908 ± 779 cpm respectively. These data are representative of 2 independent experiments.