Dietary conjugated linoleic acid modulates phenotype and effector functions of porcine CD8(+) lymphocytes

In vivo vaccination and challenge studies have demonstrated that CD8(+) lym phocytes are essential for the development of cell-mediated protection agai nst intracellular pathogens and neoplasic cells. Depletion of peripheral bl ood CD8(+) cells interferes with clearance of viruses and intracellular fun gi, induction of delayed type hypersensitivity responses and antitumoral ac tivity. In contrast to humans or mice, porcine peripheral CD8(+) lymphocyte s are characterized by a heterogeneous expression pattern (i.e., CD8 alpha beta and CD8 alpha alpha) that facilitates the study of distinctive traits among minor CD8(+) cell subsets. A factorial (2 X 2) arrangement within a s plit-plot design, with 16 blocks of two littermate, pigs as the experimenta l units for immunization treatment (i.e., unvaccinated or vaccinated with a proteinase-digested Brachyspira hyodysenteriae bacterin) and pig within bl ock as the experimental unit for dietary treatment (soybean oil or conjugat ed linoleic acid) were used to investigate the phenotypic and functional re gulation of CD8(+) cells by dietary conjugated linoleic acid (CLA). Dietary CLA supplementation induced in vivo expansion of porcine CD8(+) cells invo lving T-cell receptor (TCR)-gamma delta CD8 alpha alpha T lymphocytes, CD3( -)CD16(+)CD8 alpha alpha (a porcine natural killer cell subset), TCR alpha beta CD8 alpha beta T lymphocytes and enhanced specific CD8(+)-mediated eff ector functions (e.g., granzyme activity). Expansion of peripheral blood TC R alpha beta CD8 alpha beta cells was positively correlated (r = 0.89, P < 0.01) with increased percentages of CD8 alpha beta (+) thymocytes. Function ally, CLA enhanced the cytotoxic potential of peripheral blood lymphocytes and proliferation of TCR gamma delta CD8 alpha alpha cells. Collectively, t hese results indicate that dietary CLA enhances cellular immunity by modula ting phenotype and effector functions of CD8(+) cells involved in both adap tive and innate immunity.