Depletion of alloreactive T cells by AICD to the H-2^d alloantigen is specific.

Purified CD4⁺ responder T cells from BALB/c mice (H-2^d) mixed with OVA-specific CD4⁺ T cells derived from BALB/c (H-2^d) at a 1:1 ratio were stimulated with spleen cells from F₁ mice (H-2^dxk) in the absence or presence of anti-CD95 mAb (1 μg/mL) cross-linked by protein G (2 μg/mL) in a bulk MLC for 5 days. Remaining T cells were then challenged in vitro (A) with syngeneic spleen cells (▪), H-2^kxd alloantigen (░), or with H-2^dstimulators presenting OVA peptide (▨). In addition, remaining T-cell responders from primary cultures were transferred into irradiated F₁ recipients. On day 6 after transfer, splenic responders recovered from these recipients ex vivo (B) were tested for reactivity to syngeneic spleen cells (▪), H-2^kxd (░), as well as to OVA peptide (▨). Shown are stimulation indices from cultures harvested on day 6. Results are expressed as mean ± SD of triplicate wells and represent 1 of 2 reproducible experiments. (A) In vitro restimulation of responder T cells depleted of alloreactive cells by AICD during primary MLC resulted in a decreased reactivity to H-2^dxk compared with allogeneic T cells left untreated. However, proliferative responses of OVA-specific T cells stimulated with OVA peptide were comparable between anti-CD95–pretreated T cells and untreated controls. (B) Alloreactivity of responders isolated ex vivo after adoptive transfer of pretreated T lymphocytes to H-2^dxk was strongly impaired in contrast to untreated controls. Again, specific and comparable OVA responses could be measured in both responder populations regardless of initial depletion by AICD or no treatment.