T-regulatory lymphocyte (Treg) adoptive transfer prevented angiotensin (Ang) II-induced hypertension and microvascular injury. Scurfy mice are deficient in Treg because of a mutation in the transcription factor forkhead box P3 (Foxp3) gene. Enhanced Ang II effects in the absence of Treg would unambiguously demonstrate their vascular protective role. We hypothesized that adoptive transfer of Scurfy vs. wild-type T cells will exacerbate Ang II-induced microvascular damage in T and B-cell-deficient recombination-activating gene 1 (Rag1) knockout mice.