Phenotypic and functional characterization of pig lymphocyte populations.

Monoclonal antibodies reactive with swine lymphoid cell subpopulation antigens and with the swine major histocompatibility complex, the SLA complex, antigens are summarized. The mAb have been used to analyze swine peripheral T cell populations, the CD4+ helper T cells and the CD8+ cytotoxic/suppressor T cells. Three unique properties of swine T cells have been described. 1) There is an unusually high (25%) number of CD4+ CD8+ dual expressor T cells. 2) The ratio of CD4+ to CD8+ T cells is lower than expected; the ratio of 0.6, which is normal for pigs, only occurs in pathological conditions in humans. 3) Resting CD8+ cells preferentially express class II SLA antigens. The significance of these unusual properties of swine T cells is currently under study.