Human CD4(+) T-Cells: A Role for Low-Affinity Fc Receptors.

Anil K Chauhan

doi:10.3389/fimmu.2016.00215

Abstract

Both lymphoid and myeloid cells express Fc receptors (FcRs). Low-affinity FcRs engage circulating immune complexes, which results in the cellular activation and pro-inflammatory cytokine production. FcRs participate in the internalization, transport, and/or recycling of antibodies and antigens. Cytosolic FcRs also route these proteins to proteasomes and antigen-presentation pathways. Non-activated CD4+ T-cells do not express FcRs. Once activated, naive CD4+ T-cells express FcγRIIIa, which, upon IC ligation, provide a costimulatory signal for the differentiation of these cells into effector cell population. FcγRIIIa present on CD4+ T-cell membrane could internalize nucleic acid-containing ICs and elicit a cross-talk with toll-like receptors. FcγRIIIa common γ-chain forms a heterodimer with the ζ-chain of T-cell receptor complex, suggesting a synergistic role for these receptors. This review first summarizes our current understanding of FcRs on CD4+ T-cells. Thereafter, I will attempt to correlate the findings from the recent literature on FcRs and propose a role for these receptors in modulating adaptive immune responses via TLR signaling, nucleic acid sensing, and epigenetic changes in CD4+ T-cells.

Highlights

Immunoglobulin Fc receptors (FcRs) are expressed by many immune cells, and these receptors induce many diverse biological functions
ZAP-70-deficient patients express high levels of Syk, which is activated from FcR common γ-chain (FcR-γ) chain phosphorylation, and it plays a distinct role in transducing T-cell receptor (TCR)-mediated signal [34]
Even though earlier studies documented the presence of low-affinity FcRs on CD4+ T-cells, neglect in examining the contribution of these receptors in CD4+ T-cell responses over the past two decades has hampered progress in establishing the contribution of FcRs to adaptive immune responses

Summary

Introduction

Immunoglobulin Fc receptors (FcRs) are expressed by many immune cells, and these receptors induce many diverse biological functions. FcRs and propose a role for these receptors in modulating adaptive immune responses via TLR signaling, nucleic acid sensing, and epigenetic changes in CD4+ T-cells. This review will summarize the literature supporting the presence of FcRs on CD4+ T-cells, and further makes a case for FcγRIIIa–pSyk signaling in the modulation of TLR responses and epigenetic changes in the human peripheral CD4+ T-cells.

Results

Conclusion