Alloantibodies are responsible for elimination of donor cells in the absence of CD8 cells.

(A) To test if CD8⁺ cells were the only recipient mechanism responsible for elimination of allogeneic cells, FITC-labeled DBA/2 splenocytes were injected into CD8 KO mice and persistence was measured on days 3 to 7 (mean of 2 mice per day shown, ▪). In addition the presence of alloantibodies binding DBA/2 cells in the plasma of these mice was tested. (B) The persistence of one spleen equivalent of FITC C57BL/6 (◊) and DBA/2 splenocytes (□) when injected into B-less recipients was tested on day 3. The percentage of donor cells recovered was higher than normal because of the lack of B-cells in the spleen. (C) To test if B-less mice could still eliminate allogeneic cells in the absence of CD8⁺ cells, B-less recipients were injected with anti-CD8⁻ and FITC DBA/2 splenocytes (1 spleen equivalent per recipient) were injected on day 0 and persistence measured in the recipient spleen cells on days 3, 5, and 7 (○). Because recipient CD8⁺ cells could be detected on day 7 (data not shown), the experiments were repeated, injecting anti-CD8 intraperitoneally on days −1 and 3 and measuring the persistence of donor FITC-labeled DBA/2 cells on days 7 and 10 (▵).