Effect of different lymphocyte-bacteria ratios and bacterial toxins on apoptosis of bovine mammary gland lymphocytes

Staphylococcus aureus and Streptococcus uberis delay apoptosis of bovine mammary gland lymphocytes following intramammary infusion and in in vitro studies with lymphocyte-bacteria ratio 1:1. In this study, we investigated the effect of different lymphocyte-bacteria ratios on apoptosis of bovine mammary gland lymphocytes in vitro. We found out that lymphocyte-bacteria (S. aureus or S. uberis) ratios 1:10, 1:50 and 1:100 have different effect on apoptosis of lymphocytes than ratio 1:1. Lymphocyte apoptosis was induced 6 hours following incubation with S. aureus or S. uberis with mentioned ratios (1:10, 1:50 and 1:100). In our previous preliminary experiments focused on exploration of chemical components of bacteria on apoptosis of lymphocytes, we established the effect of muramyl dipeptide and lipopolysaccharide on lymphocyte apoptosis only in vitro. Therefore, in the second part of the present study we focused our experiments on investigation of the effect of Gram-negative bacterial toxin lipopolysaccharide on apoptosis of bovine mammary gland lymphocytes in vivo. The results of these experiments suggest that lipopolysaccharide induces apoptosis of lymphocytes following intramammary application. These data need next exploration to reveal detail effects of bacteria or bacterial toxins on lymphocyte programmed cell death in connection with inflammatory process.