Attenuated disease onset and insulitis frequency after MDC blockage. The effect of anti-MDC blocking Ab on the development of diabetes was determined using a specific neutralizing Ab against MDC. Flow cytometry analysis was performed on days 7 and 14 after adoptive cell transfer. (a) Percentage of CCR4⁺CD4⁺ T cells infiltrating the panLN’s, pancreas, and spleen and in the circulating blood (n = 3). (b) The absolute cell number of pancreas-infiltrating and panLN CCR4⁺CD4⁺ T cells. Control group, black bars (n = 3); blocking Ab group, white bars (n = 3). (c) Attenuated disease onset after MDC blockage. Open circles, control group (n = 5); filled circles, blocking Ab group (n = 5). Seventy-five percent of anti-MDC Ab-treated mice were diabetic by 38 ± 2 days; 25% of control rabbit IgG–treated mice were diabetic at 40 ± 2 days, P = 0.041. This data supports a role for CCR4 engagement in the development of insulitis and diabetes.