BIOSYNTHESIS OF B-2-INTEGRIN, INTRACELLULAR CALCIUM SIGNALING AND FUNCTIONAL-RESPONSES OF NORMAL AND CD18-DEFICIENT BOVINE NEUTROPHILS

Biosynthesis of CD11/CD18 in bovine leucocytes, intracellular Ca2+ ([C a2+](i)) signalling, chemiluminescent responses and membrane fluidity of neutrophils and the effects of D-mannose on neutrophils from contro l heifers and a heifer with bovine leucocyte adhesion deficiency (BLAD ) were measured. The synthesis of CD11/CD18 complex was clearly detect ed in leucocytes from a normal heifer, but not in a BLAD-affected heif er. The transient phase of increased [Ca2+]i was clearly detected in n eutrophils from a heifer with BLAD stimulated with opsonised zymosan, aggregated bovine immunoglobulin G or concanavalin A, whereas the sust ained phase was deficient or significantly decreased compared with con trol heifers. [Ca2+](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 sub sequent increase in [Ca2+](i) was almost identical in neutrophils from affected and control heifers. [Ca2+](i) concentration and chemilumine scent responses of neutrophils from a control heifer were clearly decr eased by treatment with anti-CD18 and anti-IgG antibodies. No differen ces in membrane fluidity were detected between neutrophils derived fro m control and CD18-deficient cattle. D-mannose binds mainly to Fc rath er than CD18 receptors, and decreased Agg-IgG induced [Ca2+](i) and th e chemiluminescent response of neutrophils. The [Ca2+](i) responses an d Agg-IgG induced chemiluminescent responses of neutrophils from contr ol heifers and a BLAD-affected heifer were inhibited by D-mannose. The characteristic changes of [Ca2+](i) signalling and functional respons es of B-2-integrin-deficient neutrophils were demonstrated.