This study examined the mitogenic response of bovine peripheral T lymphocytes to leptin, a pleiotropic hormone regulating food intake and energy expenditure. Leptin alone slightly suppressed proliferation of T lymphocytes in the presence of concanavalin A
(ConA). Leptin also inhibited proliferation of T lymphocytes induced by anti-CD3 antibody. ConA treatment activated some protein
kinases, including p44/p42MAPK and Akt/PKB, while anti-CD3 antibody treatment increased mRNA expression of suppressor of cytokine
signalling (SOCS) 3, interferon (IFN)c, interleukin (IL) 2 and IL4 in T lymphocytes. Leptin alone increased only SOCS3 mRNA
expression. Simultaneous treatment with mitogens and leptin enhanced IFNc mRNA expression but decreased IL2 mRNA expression,
without any synergistic effect on phosphorylation of protein kinases or mRNA expression of SOCS3 and IL4. These results suggest that
leptin modulates bovine T lymphocyte functions.
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