Submitted to: Journal of Dairy Science
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2007
Publication Date: 7/1/2007
Citation: Paape, M.J., Wang, Y. 2007. Effects of immunoglobulin binding on signal transduction in bovine polymorphonuclear neutrophils. Journal of Dairy Science. Interpretive Summary:
Technical Abstract: Immunoglobulins are major molecules that mediate humoral immune responses. Their functional effects on leukocytes are mediated by the cell surface receptors for the Fc domain of immunoglobulins (FcR). Ligation of FcR on human polymorphonuclear neutrophils (PMN) is capable of triggering a wide range of biological activities, including phagocytosis, secretion of granules, generation of respiratory burst, antibody-dependent cellular cytotoxicity (ADCC), and production of proinflammatory mediators and cytokines. Bovine immunoglobulins IgG2, IgM but not IgG1 binds to bovine PMN. The immunoglobulin binding pattern of bovine PMN is consistent with the major opsonic roles of IgG2 and IgM for phagocytosis by bovine PMN. In this study, changes in intracellular free calcium concentrations ([Ca2+]i) and protein tyrosine phosphorylation (PTP) induced by immunoglobulin binding to bovine PMN were investigated. Purified bovine IgG, IgG1, IgG2, IgM and heat aggregated IgG (aIgG) were used. IgG1 alone or crosslinked with a second antibody did not induce changes in [Ca2+]i and PTP. IgG2 alone or crosslinked with a second antibody and aIgG induced a strong PTP response without changes in [Ca2+]i. Crosslinking of IgG caused a rapid [Ca2+]i increase of 91 nM without a PTP response. IgM did not induce [Ca2+]i influx or PTP responses. However, crosslinking IgM with anti-bovine-IgM resulted in an increase of 115 nM in [Ca2+]i and a strong PTP response on 45, 55, 100 and 115 kD proteins. Anti-bovine-IgM antibody alone induced a similar [Ca2+]i influx and PTP response, indicating a high occupancy of IgM on bovine PMN surfaces. The immunoglobulin binding pattern of bovine PMN is consistent with the major opsonic roles of IgG2 and IgM for phagocytosis by bovine PMN. Binding of these opsonic antibodies may trigger pathways for effective PMN phagocytosis and oxidative burst activity.