Biosynthesis of B2-integrin, intracellular calcium signalling and functional responses of normal and CD18-deficient bovine neutrophils

Biosynthesis of CD11/CD18 in bovine leucocytes, intracellular Ca 2+([Ca 2+] i) signalling, chemiluminescent responses and membrane fluidity of neutrophils and the effects of D-mannose on neutrophils from control heifers and a heifer with bovine leucocyte adhesion deficiency ( BLAD) were measured. The synthesis of CD11/CD18 complex was clearly detected in leucocytes from a normal heifer, but not in a BLAD-affected heifer. The transient phase of increased [Ca 2+] i was clearly detected in neutrophils from a heifer with BLAD stimulated with opsonised zymosan, aggregated bovine immunoglobulin G or concanavalin A, whereas the sustained phase was deficient or significantly decreased compared with control heifers. [Ca 2+] i signalling of neutrophils from control heifers and a heifer with BLAD stimulated with phorbol myristate acetate via an 11b/CD18-independent pathway showed no transient phase, and the subsequent increase in [Ca 2+] i was almost identical in neutrophils from affected and control heifers. [Ca 2+] i concentration and chemiluminescent responses of neutrophils from a control heifer were clearly decreased by treatment with anti-CD18 and anti-IgG antibodies. No differences in membrane fluidity were detected between neutrophils derived from control and CD18-deficient cattle. D-mannose binds mainly to Fc rather than CD18 receptors, and decreased Agg-IgG induced [Ca 2+] i and the chemiluminescent response of neutrophils. The [Ca 2+] i responses and Agg-IgG induced chemiluminescent responses of neutrophils from control heifers and a BLAD-affected heifer were inhibited by D-mannose. The characteristic changes of [Ca 2+] i signalling and functional responses of B 2-integrin-deficient neutrophils were demonstrated.