The objective of this study was to get a better knowledge of lymphocyte apoptosis, surface expression of CD44 on lymphocytes and infammatory cytokine production (TNF-alfa, IL-4, IL-10, and TGFbeta 1) throughout inflammatory response of bovine mammary gland caused by bacterial toxin lipopolysacharide (LPS) and muramyl dipeptide as a structural unit of peptidoglycan (MDP). In the experiments, there were used LPS and MDP at the specified concentrations (5 microg and 500 microg, respectively). The inflammatory response was analysed at selected time points (24, 48, 72, and 168 h) following stimulation of the mammmary gland. As a control, the same volumes of physiological saline solution was used. The lymphocyte apoptosis and the surface expression of the CD44 on the lymphocytes were detected in the mammary gland lavages collected from the 8 clinically healthy virgin Holstein x Czech Pied heifers by flow cytometry. Further, it was analysed the concentrations of the cytokines at the same selected time points by an ELISA method. The itramammary instillation using LPS and MDP resulted in the highest lymphocyte apoptosis 48 hours after the inductor challenge. The receptor CD44 was highly correlated with the lymphocyte apoptosis occurrence. It is likely that CD44 receptor is present throughout lymphocyte apoptosis process. The cytokine concentrations obtained indicate that the cytokines may play a role in apoptosis during mammary gland infammation.