The defect of biodefense mechanisms in bovine leukocyte adhesion deficiency syndrome (BLAD) as observed from signal transduction pathway

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This project was performed to clarify the signal transduction mechanisms for NADPH oxidase activation and phagocytotis by using normal neutrophils and those with bovine leukocyte adhesion deficiency (BLAD) which was genetic deficient in beta2-integrin CR3 corresponding to the receptor of complement iC3b. Various reagents to inhibit NADPH oxidase-related signal transduction were used for this purpose. We found that inhibitors of protein kinase C (PKC), phosphatidyl inositol 3-kinase (PI 3-kinase) and p38 mitogen-activated protein kinase (p38 MAPK) were dose-dependently inhibited superoxide generation from serum-opsonized zymosan (s-OZ)-stimulated neutrophils from BLAD and normal calves, although stimulation of BLAD neutrophils with s-OZ brought about the lower generation of superoxide than that of normal neutrophils with s-OZ.These results indicated that the lack of beta2-integrin CR3 did not influence signal transduction pathways of NADPH oxidase but reduced superoxide production of NA … More DPH oxidase. This reduced NADPH oxidase activity in BLAD was partially recovered by transfusion of CD 18-positive granulocytes to diseased calf. Furthennore, PI 3-kinase and p38 MAPK but not PKC were shown to be required for phagocytotic activity in normal neutrophils. Concerning the intracellular mechanisms of NADPH oxidase activation, the p47phox, one component of NADPH oxidase, is known to be extensively phosphorylated at serines that are located among its C-terminal region and the phosphorylation is a trigger for the activation of NADPH oxidase. Using site-directed mutagenesis of p47phox and p47phox-deficient B cells from human chronic granulomatous disease (CGD), it was shown that the phosphorylation of serines 303/304, 359/370 and possibly serine 379 must take place in order to activate the oxidase. These results seem to be important in not only understanding the signal transduction mechanism of NADPH oxidase activity but also development for therapy of BLAD and p47phox-deficient CGD by the granulocyte or gene transfusion. Less