Immune interactions and survival of human RBCs in nude mice. (A) Anesthetized nude mice were infused with Dil (rhodamine)–labeled sham-treated or epi-treated normal RBCs. Blood samples collected 40 minutes after infusion were analyzed for murine immunoglobulin, which was detected using FITC-labeled antimurine immunoglobulin, bound to human RBCs. Insignificant murine immunoglobulin was bound to circulating sham- or epi-treated human normal RBCs compared with noninfused cells. One representative experiment is shown (n = 3). (B,C) Anesthetized mice were injected with a 1:1 mixture of Dil-labeled sham- (■) and DiO-labeled epi-treated (□) RBCs ([B] normal, [C] SS RBCs; n = 3 for each). Error bars show SEM of 3 different experiments. The percentages of sham- and epi-treated normal RBCs circulating in the bloodstream of animals at all times were not significantly different. A significantly greater percentage of sham-treated than epi-treated SS RBCs was retained in the circulation at all times (P < .001). (D,E) Normal RBCs were sham treated or epi treated. Sham-treated normal RBCs were detected to some degree in the spleen. Epi treatment did not lead to a significant increase in splenic trapping of normal RBCs. (F,G) Epi treatment had a significant effect on trapping of SS RBCs in the spleen compared with sham-treated cells. *P < .05 compared with sham-treated. Scale bar for panels D and F = 100 μm.