Inoculation of OVA-expressing lymphoma cells into wild-type mice elicits an OVA-specific CD8+ T cell response.

<p>(A) 1×10⁵ CD90-selected splenic T cells of mice challenged with 291OVA cells were restimulated with peritoneal macrophages (APC, antigen presenting cells) in the presence or absence of SIINFEKL peptide (p = 0.020) or with 291 parental (291PC) or OVA-expressing lymphoma cells (291OVA, p = 0.021, Mann-Whitney test, n = 5 animals/group). (B) T cell responses against OVA were monitored at different time points by flow cytometry using SIINFEKL-specific pentamers in the peripheral blood of wild-type mice inoculated with 291OVA cells. The percentage of SIINFEKL pentamer-positive CD8+ T cells increased over time as shown for one representative mouse (B, left panel). Mean values (+/− standard deviation) of percentage of SIINFEKL pentamer-positive CD8+ T cells increased over time as compiled from 5 mice (B, right panel). (C) After inoculation of 1×10⁵ 291 parental or 291OVA cells, the developing lymphomas were analyzed by immunohistochemistry for infiltration of CD3-positive (peroxidase brown staining) and perforin expressing (alkaline phosphatase red staining) cells (C, left panel). CD3− and perforin-positive cells were quantified in blinded fashion by counting 10 high power fields (HPF, 400×) per section. Values are given as a mean ± standard error of the mean (C, right panel). Only CD3-positive and CD3/perforin-double positive cells (CD3/HPF) were regarded as T cells, whereas single perforin-positive cells were considered to be NK cells and excluded from the analysis. For each group 8–15 sections were analyzed. Mann Whitney-U test was used for comparison.