DC vaccination against endogenously expressed tumor antigen is enhanced by depletion of CD25⁺ cells before vaccination. RIP-OVA^lo mice on C57Bl/6 background expressing OVA under the control of rat insulin promoter were vaccinated using DCs nucleofected with pGO plasmid (pGO) (A). A group of mice were depleted of CD25⁺ cells 5 days before vaccination (pGO CD25dep). (B) Depletion of CD25⁺ cells 5 days before immunization with subcutaneous OVA in IFA does not increase lymphocyte infiltration into pancreatic islets within 2 weeks. Pancreases from 4 RIP-OVA^lo mice in each group were analyzed in a blinded fashion for the level of lymphocytic infiltration (insulitis) in individual islets (each graded from 0 to 3 to count a score for each pancreas) using hematoxylin and eosin staining and light microscopy. At least 50 islets per pancreas were analyzed. P values were calculated using the Student t test. Black bars show insulitis score in untreated mice plus or minus the standard error of mean, white bars indicate OVA immunized mice, and gray bars indicate OVA-immunized and CD25-depleted mice.