Effects of fatty acid mixtures on proliferation of peripheral blood mononuclear cells in dairy cows

This in vitro study was performed to assess the effects of three different mixtures of nonesterifed fatty acids (NEFA) on mitogen-driven proliferation of peripheral blood mononuclear cells (PBMC) in dairy cows. Substantially, the three mixtures differed for n-6 to n-3 fatty acids (FA) ratio and were intended to mimic plasma NEFA composition of cows given fat supplements with different n-6 to n-3 FA ratio. PBMC from six Holstein heifers were cultured in media containing three different mixtures of oleic, palmitic, stearic, linoleic, palmitoleic, or linolenic acid at concentrations mimicking different degree of lipomobilisation. Proliferation of PBMC was stimulated by concanavalin A or pokeweed mitogen (PWM). Low concentrations of the three mixtures (62.5 and 125 µmol/l), did not affect the ability of PBMC to proliferate. Concentrations of the three mixtures mimicking medium-intense lipomobilisation (500, 1,000 and 1,500 µmol/l) impaired to the same extent proliferation of PBMC. The addition to cultures of the three mixtures at concentration of 250 µmol/l, impaired the proliferation only in PBMC stimulated with PWM. Even in this case, the three mixtures did not exert differential effects on PBMC proliferation. Present results reinforce the hypothesis that high concentrations of plasma NEFA play a role in the immunosuppression taking place in cows undergoing intense lipomobilisation, and authorize to suggest that under these conditions different composition of plasma NEFA in terms of different n-6 to n-3 FA ratio cannot prevent their negative effects on lymphocyte proliferation.