MHC restricted, antigen specific, cytokine dependent T-cell lines were established from peripheral blood mononuclear cells (PBMC) of NIH minipigs that were challenge inoculated with Trichinella spiralis. Swine lymphocyte antigen (SLA) inbred NIH minipigs of the SLA a/a (aa) haplotype can be divided into Responder (R) and Non-responder (NR) phenotypes on the basis of their ability to destroy encysted muscle larval (ML) forms of the parasite T. spiralis. When orally inoculated with 300 infectious ML and challenge inoculated with 10,000 ML, R pigs are able to mount an immune attack against encysted ML resident in host muscle cells since the primary inoculation. Because T-lymphocyte mediated mechanisms are likely to be operative in this response, a series of T-lymphocyte cell lines was established from PBMC of ten aa minipigs 10 days after the challenge infection with T. spiralis. These T-lymphocyte lines showed antigen specific, cytokine dependent proliferation in response to T. spiralis antigen stimulation. T-lymphocyte cell lines from R and NR pigs were compared and found to be similar in the magnitude of proliferative responses, in the duration of antigen specificity, and in the alterations in T-lymphocyte subsets and cell surface phenotype after antigen stimulation. In vitro antigen stimulation of T-lymphocyte cell lines and evaluation of small lymphocytes and lymphoblasts by density gradient centrifugation, immunofluorescent staining and flow cytometry, revealed that up to 55% of the cells were lymphoblasts at 4 days after stimulation, and that the majority of the lymphoblast population expressed CD4 and CD8, as well as the interleukin-2 receptor and the Class II alloantigen, SLA-DR (DR+). These results indicate that pig T-lymphocytes of the CD4+CD8+ phenotype may be involved in the anamnestic cell mediated immune response to T. spiralis.