The studies on the mechanism of intravenous immunoglobulin (IVIG)-induced inhibitory functions on neutrophil recruitments

The goal of this proposal is to elucidate the function/mechanism of intravenous immunoglobulin (IVIG) on the recruitments of neutrophils. This study may provide more detail therapeutic functions of IVIG on acute or chronic inflammatory diseases and shed a new lead for the future drug designing in pharmaceutical industries, leading to benefit patients with better options for treatments. We have been demonstrated that IVIG can reverse the sickle crises in transgenic sickle cell disease mice (SCD) by reducing neutrophil recruitments and sickle erythrocyte-neutrophil interactions, leading to improved blood flow. Moreover, further analyses of leukocyte rolling behavior revealed that IVIG significantly increased the average leukocyte rolling velocity, indicating that IVIG specifically alters the functions of adhesions molecules mediating leukocyte slow rolling. Slow rolling velocity in leukocytes has been largely associated with E selectin and E-selectin ligands (ESLs) and β2 integrins coupled with their endothelial counter-part receptors, intercellular adhesion molecules (ICAMs). Therefore, IVIG may target these adhesion molecules expressed either on neutrophils or endothelium in expression and/or binding affinity resulting in increased rolling velocity and reduced the number of recruited neutrophils in the inflamed venues of mice. However, IVIG-induced inhibitory effects on blocking leukocyte adherent onto vascular wall still remain largely unknown. In this proposal, we will first confirm this inhibitory effect on leukocyte recruitments not only shown in SCD mice but also appeared to in normal wild type mice (C57BL/6). This will provide normal pharmaceutical properties of IVIG on leukocytes. The adhesion patterns including leukocyte rolling flux, the average velocity of leukocyte rolling and the number of leukocyte adhesion per 100μm segment of venule plus the microcirculation parameters such as blood flow rate, shear stress and shear rate will carefully characterized and documented using intravital microscopy in IVIG-treated and albumin-treated mice. Following the evaluation on the effects of IVIG on leukocyte recruitments in wild type mice, we will work on the functional analysis of IVIG by determining the ligands of IVIG, IVIG-modulated adhesion molecules and IVIG- receptors induced signaling transduction pathway. In additional to acknowledge the therapeutic proprieties of IVIG in acute /chronic inflammatory diseases or immune related disease, it may inspire us to design new drugs with higher potency and less site effects by mimicking inhibitory mechanism of IVIG on neutrophils recruitments.