CD4 and diabetes mellitus: Transfer of as few as 1×106 p524-expanded CD4+CD25+ T cells per mouse markedly prevented/delayed the development of diabetes for as long as 25 wk after transfer (Figure 5a), whereas transfer of similar or even 3-fold greater numbers of p509 or p530-expanded CD4+CD25+ T cells only had a slight preventive effect on diabetes incidence (Figure 5a and 5b).