Differential signal transduction, membrane trafficking, and immune effector functions mediated by FcγRI versus FcγRIIa

• Published in: Blood Vol. 114; no. 2; pp. 318 - 327
• Main Authors: Dai, Xilei, Jayapal, Manikandan, Tay, Hwee Kee, Reghunathan, Renji, Lin, Gen, Too, Chien Tei, Lim, Yan Ting, Chan, Soh Ha, Kemeny, D. Michael, Floto, R. Andres, Smith, Kenneth G.C., Melendez, Alirio J., MacAry, Paul A.
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 09-07-2009; Americain Society of Hematology
• Subjects: Biological and medical sciences; Hematologic and hematopoietic diseases; Medical sciences; FcγRIIA receptor; Signal transduction; Hematology; Immunoglobulin receptor; FcγRI receptor; Effector; Immunity; Comparative study
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2008-10-184457

Receptors for the fragment crystallizable region of immunoglobulin-G (FcγRs) play an important role in linking the humoral and cellular arms of the immune response. In this study, we present a comprehensive functional comparison of 2 human Fc-receptors, FcγRI and FcγRIIa. Activation of FcγRI results in a novel signaling cascade that links phospholipase D1 to sphingosine kinase-1 in U937 cells and primary human monocytes. This induces the expression of proinflammatory mediators and is associated with trafficking of immune complexes into human leukocyte antigen-DM positive antigen-processing compartments coupled with improved MHC class II–mediated antigen presentation to T lymphocytes. In contrast, activation of FcγRIIa elicits signaling through phospholipase Cγ1, resulting in increases in intracellular calcium, activation of nicotinamide adenine dinucleotide phosphate-oxidative burst, and differential membrane trafficking combined with impaired antigen presentation and proinflammatory cytokine expression. These data provide a mechanistic insight into the disparate activities associated with Fc receptors in immunity, namely, reinforcement of immune responses through stimulation of proinflammatory signaling and antigen presentation, versus the maintenance of immunologic homeostasis through the noninflammatory clearance of immune complexes.