PBMC were obtained, HLA haplotype was determined, and they were processed and cryopreserved as described [18] . ELISpot assays with human PBMCs were similar to those with murine splenocytes but used α-human IFN-γ mAb (1-D1K) with biotinylated α-human IFN-γ mAb (7B6-1) with 2 × 10 5 PBMCs per well. All antibodies and reagents used for ELISpot assays were from Mabtech (Cincinnati, OH). Antibodies were monoclonal antibodies. Both murine and human cells were plated in at least 3 replicate wells for each condition. Results were expressed as number of spot forming cells (SFCs) per 10 6 PBMCs or per 10 6 murine splenocytes.