Faculty Bibliography

Introduction: This study explored the role of a novel CR3 agonist to attenuate pro-inflammatory signaling in subjects with common and variant ITGAM polymorphism, rs1143679. The mechanism underlying initiation and perpetuation of inflammation - with eventual end organ injury - in Systemic Lupus Erythemasosus (SLE) is not yet defined. Equally unclear are mechanisms to attenuate such inflammation. An important candidate for initiation and perpetuation of the inflammatory response may be the chronic stimulation of resident leukocytes through toll like receptors (TLR). Complement Receptor 3 (CR3), a heterodimeric receptor on the surface of various types of leucocytes, is known to decrease proinflammatory signals by dendritic cells when ligated to iC3b. The goal of this study was to evaluate whether a TLR-mediated pro-inflammatory stimulus is attenuated by a novel iC3b mimetic specific for CR3 - known as LA1 - on macrophages expressing CR3. ITGAM polymorphism rs1143679, encoding for a non-conserved R77H substitution CD11b alpha chain of CR3 is known to be associated with SLE across various ethnic groups. While the polymorphism is theorized to affect ligand binding to CR3 the functional significance of the polymorphism is unknown. A sub-goal was to evaluate if rs1143679 carrier status attenuated the effect of LA1. Patients and Methods: The effect of LA1 on basal and stimulated responses by macrophages of human subjects (twenty healthy donors) was evaluated. Rs1143679 carrier status of subjects was determined by allelic discrimination. Macrophages derived from CD14+ monocytes of healthy human donors were treated with R848 (a specific TLR7 ligand, 1 uM) and hY3 (2.5 ug), with and without LA1 (a recently described CR3 agonist, 15 uM). Quantification of TNFalpha secretion, the readout of TLR7 activation, was assessed by ELISA. Results: Treatment of macrophages with R848 significantly stimulated TNFalpha release compared with macrophages alone (1265 +/- 297 pg/ml versus 26 +/- 30 pg/ml, respectively, p = 0!