Reduction in Ampd3^−/− naive T cells is triggered by T-cell–extrinsic factor(s). (A) Donor CD45.1⁺ T cells were transferred into CD45.2⁺Ampd3^+/+ and Ampd3^−/− hosts. The percentages of naive CD4⁺ and naive CD8⁺ T cells of transferred CD45.1⁺ donors and CD45.2⁺ hosts are shown (n = 4 for wild-type and Ampd3^−/− hosts). (B) Packed red blood cells (RBC) from wild-type mice and Ampd3^−/− mice were transfused into CD45.1⁺ hosts. Percentages of CD45.1⁺ naive CD4⁺ T cells and naive CD8⁺ T cells were analyzed by flow cytometry. (C) MFI of CD44 and CD62L of host CD4⁺ and CD8⁺ T cells after receiving blood transfusion. (D) The same groups of mice were analyzed again 40 days after the final transfusion (n = 4 and n = 5 for hosts receiving wild-type and Ampd3^−/− red blood cells, respectively). ***P ≤ .001. ns, not significant (P > .05).