Objective—To determine whether proinflammatory
mediators and glucocorticoids affect CD62L(L-selectin)
expression on peripheral blood neutrophils
from cows in various stages of lactation.
Animals—100 healthy dairy cows during early (13.1 ±
0.79 days after parturition; n = 31), peak (58.7 ± 1.64
days after parturition; 31), and mid (137.2 ± 2.59 days
after parturition; 38) lactation.
Procedure—In vitro effects of relevant proinflammatory
mediators that are released in response to mastitis
caused by gram-negative bacteria such as
lipopolysaccharide (endotoxin), tumor necrosis factor-α, and platelet-activating factor (PAF) on CD62L
expression on bovine neutrophils were assessed by
flow cytometry. Influences of cortisol and dexamethasone
on CD62L expression on bovine neutrophils
were also investigated.
Results—Basal CD62L expression on neutrophils
from cows during early, peak, and mid lactation
were similar. Lipopolysaccharide and tumor necrosis
factor-α had no effect on CD62L expression on
neutrophils from cows at any stage of lactation.
Conversely, PAF elicited a time- and dose-dependent,
down regulatory effect on CD62L expression.
However, no differential shedding of CD62L from
neutrophils of cows at any stage of lactation were
detected. In addition, no effects on CD62L expression
on bovine neutrophils after whole blood incubation
with cortisol or dexamethasone were
observed. Incubation with glucocorticoids did not
prevent the down regulatory effect of PAF on
Conclusions and Clinical Relevance—Comparable
basal CD62L expression on bovine neutrophils and
equal amounts of CD62L shedding from bovine neutrophils
during all stages of lactation suggest that variations
in CD62L density are not a likely cause of susceptibility
of cows to coliform-induced mastitis during
early lactation. (Am J Vet Res 2004;225:1421–1426)