Bovine monocyte-derived dendritic cell populations from animals in late gestation show altered response to E. coli (VET2P.1039)

During late gestation the bovine immune system is less capable of eliminating pathogens. Most new intra-mammary infections occur in late gestation, and the majority of these infections are caused by E. coli. Unlike non-pregnant, lactating cows, late gestation cows are unable to elicit an effective inflammatory response to intra-mammary infection caused by E. coli. During pregnancy, the immune system appears to shift to a humoral, anti-inflammatory, so called T helper 2 bias with increased tolerance. Dendritic cells are antigen presenting cells that orchestrate activation and differentiation of naive T cells, and they are hypothesized to play a key role in directing the T helper 2 bias and immune tolerance observed in gestation. We stimulated monocyte-derived dendritic cells with E. coli and compared responses from late gestation cows to those of non-pregnant cows. Results show monocyte-derived dendritic cells from late gestation cows have altered surface molecule expression and cytokine production compared to those from non-pregnant cows. Our findings support the hypothesis that late gestation bovine dendritic cells are likely to produce suboptimal T cell activation in response to E. coli antigens, and play a role in observed immune-bias in pregnancy. In addition, altered dendritic cell function in gestation may impede current, routine vaccination regiments in late gestation. Future work will identify likely pregnancy-factors that modulate bovine dendritic cell responses.