Objective: To determine expression of the beta 2-integrin (CD18) family of adhesion molecules and L-selectin (CD62L) on neutrophils from periparturient cows and calves.
Animals: 8 periparturient Holstein cows and 9 Holstein calves.
Procedure: Constitutive CD18 and CD62L expression on neutrophils was determined by flow cytometry, using specific monoclonal antibodies. Platelet-activating factor was used to activate neutrophils in vitro to measure down-regulation of CD62L and up-regulation of CD18 on activated neutrophils.
Results: Mean values for constitutive and platelet-activating factor-stimulated CD18 expression on neutrophils from cows and calves were highest at parturition, then decreased during the first 24 hours after parturition on calf neutrophils, whereas CD62L expression decreased markedly by 9 to 24 hours after parturition on cow and calf neutrophils. Constitutive amounts of CD18 and CD62L on cow neutrophils returned to prepartum values by day 3 after parturition. Amounts of CD18 expression on calves' neutrophils recovered by 1 week of age, but did not reach original birth values, whereas CD62L expression exceeded birth values by day 3 after parturition. Cows had leukocytosis (neutrophilia), with a doubling of circulating neutrophils 9 hours after calving that was inversely correlated with CD62L expression on neutrophils.
Conclusions and clinical relevance: Low amounts of CD62L and CD18 on calf neutrophils and of CD62L on neutrophils from cows for several days after parturition may result in impaired inflammatory response. Low CD62L expression may contribute to increased susceptibility to disease.