ENHANCED EXPRESSION OF FC-RECEPTORS ON NEUTROPHILS FROM CALVES WITH LEUKOCYTE ADHESION DEFICIENCY

The expression of Fc receptors for immunoglobulin G(IgG) and concanava lin A (con A)-binding receptors, luminol-dependent chemiluminescent (L DCL) responses, and the effect of anti-bovine IgG on LDCL responses we re evaluated in neutrophils from Holstein calves with leukocyte adhesi on deficiency (BLAD). Neutrophils from affected calves showed a 2.1- t o 2.5-fold increase in Fc receptor expression compared with those of c ontrol calves by flow cytometric analysis. Con A-binding activities of neutrophils from affected calves were similar to those of control cal ves. Neutrophils from a calf with BLAD, when stimulated with zymosan o psonized with bovine serum (OPZ), heat-aggregated bovine IgG (Agg-bovi ne IgG), sheep red blood cells (SRBC) sensitized with anti-SRBC antibo dy (SRBC-anti-SRBC Ab), or con A had LDCL responses of 36 (P < 0.05), 77, 126 and 119% of peak LDCL values of controls, respectively. The NB T-reducing value of neutrophils from a calf with BLAD when stimulated with Agg-bovine IgG after pretreatment with anti-bovine IgG was 116.5% of the values of neutrophils from control calves, but the difference was not significant, The LDCL responses of neutrophils from a control calf and a calf with BLAD stimulated with OPZ were inhibited markedly by pre-incubation with anti-bovine IgG antiserum at concentrations ran ging from 1.25 to 20 or 40 mu g/ml. Although an increase in Fc recepto r expression on neutrophils from calves with BLAD was observed, the LD CL responses stimulated with SRBC-anti-SRBC Ab and NBT-reducing activi ty stimulated with Agg-bovine IgG after pretreatment with anti-bovine IgG did not correlate significantly with the increased Fc receptor exp ression. These results support that neutrophil functions mediated by t he Fc receptors are associated synergistically with the presence of th e complement receptor type 3 (CR3)(CD11b/CD18).