Costimulatory Effects of Complement Receptor Type 3 and Fc Receptor for IgG (FcγR) on Superoxide Production and Signal Transduction in Bovine Neutrophils

Abstract

The present study evaluated the costimulatory effects of complement receptor type 3 (CR3) and Fc receptor for IgG (FcγR) on superoxide production and intracellular signal transduction in bovine neutrophils. Stimulation with opsonized zymosan (OPZ) and heat-aggregated bovine IgG (Agg-IgG) resulted in much greater superoxide production and chemiluminescent (CL) responses in normal neutrophils compared with those stimulated with OPZ or Agg-IgG only. Superoxide production and CL response were closely associated with the stimulant-induced rise of the intracellular calcium ([Ca²⁺]_i) concentration, amount of tyrosine phosphorylated 100 kDa protein, and activation of p38 mitogen-activated protein kinase (p38 MAPK). No costimulatory effect was found for these receptors on superoxide production in CR3-deficient neutrophils. Costimulation of CR3 and FcγR on bovine neutrophils leads to enhancement of superoxide production and their signaling pathways and appears to be associated with enhancement of neutrophil functions.