Biology:Fc receptor

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Short description: Surface protein important to the immune system
Immunoglobulin-like receptor
Fc receptor schematic.svg
Schematic diagram showing Fc receptor interaction with an antibody-coated microbial pathogen
Identifiers
SymbolFc receptor
Membranome10

In immunology, an Fc receptor is a protein found on the surface of certain cells – including, among others, B lymphocytes, follicular dendritic cells, natural killer cells, macrophages, neutrophils, eosinophils, basophils, human platelets, and mast cells – that contribute to the protective functions of the immune system. Its name is derived from its binding specificity for a part of an antibody known as the Fc (fragment crystallizable) region. Fc receptors bind to antibodies that are attached to infected cells or invading pathogens. Their activity stimulates phagocytic or cytotoxic cells to destroy microbes, or infected cells by antibody-mediated phagocytosis or antibody-dependent cell-mediated cytotoxicity. Some viruses such as flaviviruses use Fc receptors to help them infect cells, by a mechanism known as antibody-dependent enhancement of infection.[1]

Classes

There are several different types of Fc receptors (abbreviated FcR), which are classified based on the type of antibody that they recognize. The Latin letter used to identify a type of antibody is converted into the corresponding Greek letter, which is placed after the 'Fc' part of the name. For example, those that bind the most common class of antibody, IgG, are called Fc-gamma receptors (FcγR), those that bind IgA are called Fc-alpha receptors (FcαR) and those that bind IgE are called Fc-epsilon receptors (FcεR). The classes of FcR's are also distinguished by the cells that express them (macrophages, granulocytes, natural killer cells, T and B cells) and the signalling properties of each receptor.[2]

Fc-gamma receptors

All of the Fcγ receptors (FcγR) belong to the immunoglobulin superfamily and are the most important Fc receptors for inducing phagocytosis of opsonized (marked) microbes.[3] This family includes several members, FcγRI (CD64), FcγRIIA (CD32), FcγRIIB (CD32), FcγRIIIA (CD16a), FcγRIIIB (CD16b), which differ in their antibody affinities due to their different molecular structure.[4] For instance, FcγRI binds to IgG more strongly than FcγRII or FcγRIII does. FcγRI also has an extracellular portion composed of three immunoglobulin (Ig)-like domains, one more domain than FcγRII or FcγRIII has. This property allows FcγRI to bind a sole IgG molecule (or monomer), but all Fcγ receptors must bind multiple IgG molecules within an immune complex to be activated.[5]

The Fc-gamma receptors differ in their affinity for IgG and likewise the different IgG subclasses have unique affinities for each of the Fc gamma receptors.[6] These interactions are further tuned by the glycan (oligosaccharide) at position CH2-84.4 of IgG.[6] For example, by creating steric hindrance, fucose containing CH2-84.4 glycans reduce IgG affinity for FcγRIIIA.[6] In contrast, G0 glycans, which lack galactose and terminate instead with GlcNAc moieties, have increased affinity for FcγRIIIA.[6]

Neonatal Fc Receptor

Another FcR is expressed on multiple cell types and is similar in structure to MHC class I. This receptor also binds IgG and is involved in preservation of this antibody.[7] However, since this Fc receptor is also involved in transferring IgG from a mother either via the placenta to her fetus or in milk to her suckling infant, it is called the neonatal Fc receptor (FcRn).[8][9] Recently, research suggested that this receptor plays a role in the homeostasis of IgG serum levels.

Fc-alpha receptors

Only one Fc receptor belongs to the FcαR subgroup, which is called FcαRI (or CD89).[10] FcαRI is found on the surface of neutrophils, eosinophils, monocytes, some macrophages (including Kupffer cells), and some dendritic cells.[10] It is composed of two extracellular Ig-like domains, and is a member of both the immunoglobulin superfamily and the multi-chain immune recognition receptor (MIRR) family.[3] It signals by associating with two FcRγ signaling chains.[10] Another receptor can also bind IgA, although it has higher affinity for another antibody called IgM.[11] This receptor is called the Fc-alpha/mu receptor (Fcα/μR) and is a type I transmembrane protein. With one Ig-like domain in its extracellular portion, this Fc receptor is also a member of the immunoglobulin superfamily.[12]

Fc-epsilon receptors

Two types of FcεR are known:[3]

  • the high-affinity receptor FcεRI is a member of the immunoglobulin superfamily (it has two Ig-like domains). FcεRI is found on epidermal Langerhans cells, eosinophils, mast cells and basophils.[13][14] As a result of its cellular distribution, this receptor plays a major role in controlling allergic responses. FcεRI is also expressed on antigen-presenting cells, and controls the production of important immune mediators called cytokines that promote inflammation.[15]
  • the low-affinity receptor FcεRII (CD23) is a C-type lectin. FcεRII has multiple functions as a membrane-bound or soluble receptor; it controls B cell growth and differentiation and blocks IgE-binding of eosinophils, monocytes, and basophils.[16]

Summary table

Receptor name Principal antibody ligand Affinity for ligand Cell distribution Effect following binding to antibody
FcγRI (CD64) IgG1 and IgG3 High (Kd ~ 10−9 M) Macrophages
Neutrophils
Eosinophils
Dendritic cells 		Phagocytosis
Cell activation
Activation of respiratory burst
Induction of microbe killing
FcγRIIA (CD32) IgG Low (Kd > 10−7 M) Macrophages
Neutrophils
Eosinophils
Platelets
Langerhans cells 		Phagocytosis
Degranulation (eosinophils)
FcγRIIB1 (CD32) IgG Low (Kd > 10−7 M) B Cells
Mast cells 		No phagocytosis
Inhibition of cell activity
FcγRIIB2 (CD32) IgG Low (Kd > 10−7 M) Macrophages
Neutrophils
Eosinophils 		Phagocytosis
Inhibition of cell activity
FcγRIIIA (CD16a) IgG Low (Kd > 10−6 M) NK cells
Macrophages (certain tissues) 		Induction of antibody-dependent cell-mediated cytotoxicity (ADCC)
Induction of cytokine release by macrophages
FcγRIIIB (CD16b) IgG Low (Kd > 10−6 M) Eosinophils
Macrophages
Neutrophils
Mast cells
Follicular dendritic cells 		Induction of microbe killing
FcεRI IgE High (Kd ~ 10−10 M) Mast cells
Eosinophils
Basophils
Langerhans cells
Monocytes 		Degranulation
Phagocytosis
FcεRII (CD23) IgE Low (Kd > 10−7 M) B cells
Eosinophils
Langerhans cells 		Possible adhesion molecule
IgE transport across human intestinal epithelium
Positive-feedback mechanism to enhance allergic sensitization (B cells)
FcαRI (CD89) IgA Low (Kd > 10−6 M) Monocytes
Macrophages
Neutrophils
Eosinophils 		Phagocytosis
Induction of microbe killing
Fcα/μR (CD351) IgA and IgM High for IgM, Mid for IgA B cells
Mesangial cells
Macrophages 		Endocytosis
Induction of microbe killing
FcμR[17] IgM (unknown) Human FcμR is predominantly expressed by lymphocytes, but not by phagocytes [18] function has not been fully elucidated / diverse [19]
FcRn IgG high in acidic cellular endosomes
low in pH neutral extracellular environment 		Monocytes
Macrophages
Dendritic cells
Epithelial cells
Endothelial cells
Hepatocytes
 Transfers IgG from a mother to fetus through the placenta
Transfers IgG from a mother to infant in milk
Protects IgG from degradation
Transfers IgG across endothelial/epithelial layers

Functions

An antibody has Fab (fragment, antigen-binding) and Fc (fragment, crystallizable) regions. Fc receptors bind to the Fc region.

Fc receptors are found on a number of cells in the immune system including phagocytes like macrophages and monocytes, granulocytes like neutrophils and eosinophils, and lymphocytes of the innate immune system (natural killer cells) or adaptive immune system (e.g., B cells).[20][21][22] They allow these cells to bind to antibodies that are attached to the surface of microbes or microbe infected cells, helping these cells to identify and eliminate microbial pathogens. The Fc receptors bind the antibodies at their Fc region (or tail), an interaction that activates the cell that possesses the Fc receptor.[23] Activation of phagocytes is the most common function attributed to Fc receptors. For example, macrophages begin to ingest and kill an IgG-coated pathogen by phagocytosis following engagement of their Fcγ receptors.[24] Another process involving Fc receptors is called antibody-dependent cell-mediated cytotoxicity (ADCC). During ADCC, FcγRIII receptors on the surface of natural killer (NK) cells stimulate the NK cells to release cytotoxic molecules from their granules to kill antibody-covered target cells.[25] FcεRI has a different function. FcεRI is the Fc receptor on granulocytes, that is involved in allergic reactions and defense against parasitic infections. When an appropriate allergic antigen or parasite is present, the cross-linking of at least two IgE molecules and their Fc receptors on the surface of a granulocyte will trigger the cell to rapidly release preformed mediators from its granules.[3]

Signaling mechanisms - Fc gamma receptors

Activation

Fc gamma receptors belong to the group of non-catalytic tyrosine-phosphorylated receptors which share a similar signalling pathway involving phosphorylation of tyrosine residues.[26] The receptors generate signals within their cells through an important activation motif known as an immunoreceptor tyrosine-based activation motif (ITAM).[27] An ITAM is a specific sequence of amino acids (YXXL) occurring twice in close succession in the intracellular tail of a receptor. When phosphate groups are added to the tyrosine (Y) residue of the ITAM by membrane-anchored enzymes of the Src kinase family, a signaling cascade is generated within the cell. This phosphorylation reaction typically follows interaction of an Fc receptor with its ligand. An ITAM is present in the intracellular tail of FcγRIIA, and its phosphorylation induces phagocytosis in macrophages. FcγRI and FcγRIIIA do not have an ITAM but can transmit an activating signal to their phagocytes by interacting with another protein that does. This adaptor protein is called the Fcγ subunit and, like FcγRIIA, contains the two YXXL sequences that are characteristic of an ITAM.

Inhibition

The presence of only one YXXL motif is not sufficient to activate cells, and represents a motif (I/VXXYXXL) known as an immunoreceptor tyrosine-based inhibitory motif (ITIM). FcγRIIB1 and FcγRIIB2 have an ITIM sequence and are inhibitory Fc receptors; they do not induce phagocytosis. Inhibitory actions of these receptors are controlled by enzymes that remove phosphate groups from tyrosine residues; the phosphatases SHP-1 and SHIP-1 inhibit signaling by Fcγ receptors.[28] Binding of ligand to FcγRIIB leads to phosphorylation of the tyrosine of the ITAM motif. This modification generates the binding site for the phosphatase, a SH2 recognition domain. The abrogation of ITAM activation signaling is caused by inhibition of protein tyrosine kinases of Src family, and by hydrolyzing the membrane PIP3 interrupting the further downstream signaling by the activating receptors, such as activating FcγRs, TCR, BCR and cytokine receptors (e.g. c-Kit).[29]

The negative signaling by FcγRIIB is mainly important for regulation of activated B cells. The positive B cell signaling is initiated by binding of foreign antigen to surface immunoglobulin. The same antigen-specific antibody is secreted and it can feedback-suppress, or promote negative signaling. This negative signaling is being provided by FcγRIIB.:[30] Experiments using B cell deletion mutants and dominant-negative enzymes have firmly established an important role for SH2-domain-containing inositol 5-phosphatase (SHIP) in negative signaling. Negative signaling through SHIP appears to inhibit the Ras pathway through SH2 domain competition with Grb2 and Shc and may involve consumption of intracellular lipid mediators that act as allosteric enzyme activators or that promote entry of extracellular Ca2+.[31]

Cellular activation

Fc receptors recognize microbes that have been bound by antibodies. The interaction between the bound antibodies and the cell surface Fc receptor activates the immune cell to kill the microbe. This example shows the phagocytosis of an opsonized microbe.

On phagocytes

When IgG molecules, specific for a certain antigen or surface component, bind to the pathogen with their Fab region (fragment antigen binding region), their Fc regions point outwards, in direct reach of phagocytes. Phagocytes bind those Fc regions with their Fc receptors.[24] Many low affinity interactions are formed between receptor and antibody that work together to tightly bind the antibody-coated microbe. The low individual affinity prevents Fc receptors from binding antibodies in the absence of antigen, and therefore reduces the chance of immune cell activation in the absence of infection. This also prevents agglutination (clotting) of phagocytes by antibody when there is no antigen. After a pathogen has been bound, interactions between the Fc region of the antibody and the Fc receptors of the phagocyte results in the initiation of phagocytosis. The pathogen becomes engulfed by the phagocyte by an active process involving the binding and releasing of the Fc region/Fc receptor complex, until the cell membrane of the phagocyte completely encloses the pathogen.[32]

On NK cells

The Fc receptor on NK cells recognize IgG that is bound to the surface of a pathogen-infected target cell and is called CD16 or FcγRIII.[33] Activation of FcγRIII by IgG causes the release of cytokines such as IFN-γ that signal to other immune cells, and cytotoxic mediators like perforin and granzyme that enter the target cell and promote cell death by triggering apoptosis. This process is known as antibody-dependent cell-mediated cytotoxicity (ADCC). FcγRIII on NK cells can also associate with monomeric IgG (i.e., IgG that is not antigen-bound). When this occurs, the Fc receptor inhibits the activity of the NK cell.[34]

On mast cells

Activation of mast cell degranulation by IgE interaction with FcεRI. 1 = antigen; 2 = IgE; 3 = FcεRI; 4 = preformed mediators (histamine, proteases, chemokines, heparin); 5 = granules; 6 – mast cell; 7 – newly formed mediators (prostaglandins, leukotrienes, thromboxanes, platelet-activating factor)

IgE antibodies bind to antigens of allergens. These allergen-bound IgE molecules interact with Fcε receptors on the surface of mast cells. Activation of mast cells following engagement of FcεRI results in a process called degranulation, whereby the mast cell releases preformed molecules from its cytoplasmic granules; these are a mixture of compounds including histamine, proteoglycans, and serine proteases.[35] Activated mast cells also synthesize and secrete lipid-derived mediators (such as prostaglandins, leukotrienes, and platelet-activating factor) and cytokines (such as interleukin 1, interleukin 3, interleukin 4, interleukin 5, interleukin 6, interleukin 13, tumor necrosis factor-alpha, GM-CSF, and several chemokines.[36][37] These mediators contribute to inflammation by attracting other leukocytes.

On eosinophils

Large parasites like the helminth (worm) Schistosoma mansoni are too large for ingestion by phagocytes. They also have an external structure called an integument that is resistant to attack by substances released by macrophages and mast cells. However, these parasites can become coated with IgE and recognized by FcεRII on the surface of eosinophils. Activated eosinophils release preformed mediators such as major basic protein, and enzymes such as peroxidase, against which helminths are not resistant.[38][39] The interaction of the FcεRII receptor with the Fc portion of helminth bound IgE causes the eosinophil to release these molecules in a mechanism similar to that of the NK cell during ADCC.[40]

On T lymphocytes

CD4+ T cells (mature Th cells) provide help to B cells that produce antibodies. Several subsets of activated effector CD4+ T cells are observed in disease pathology. Earlier studies summarized by Sanders and Lynch in 1993 suggested critical roles for FcRs in CD4+ T cell mediated immune responses and proposed the formation of a joint signaling complex among FcRs and TCR on the cell surface.[41][42][43][44] Chauhan and coworkers reported the colocalization of the labeled ICs with the CD3 complex on activated CD4+ T cell surface, which thus suggest the coexistence of FcRs together with TCR complex.[45] Both of these receptors are observed forming an apical structure on the membrane of activated CD4+ T cells, suggesting the lateral movement of these receptors.[46] Co-migration of FcRs with TCR and BCR complex is observed on the cells surface and T:B cell cytoconjugates show this coexistence at the point of contact.[47] An earlier review suggested that the expression of FcRs on CD4+ T cells is an open question.[48] This established the current paradigm that T cells do not express FcRs and these findings were never challenged and experimentally tested.[49] Chauhan and coworkers showed binding of immune complexes (ICs), the FcR ligand to activated CD4+ T cells.[49] CD16a expression is induced in the activated human naïve CD4+ T cells, which express CD25, CD69, and CD98 and ligation to ICs leads to generation of effector memory cells.[50] CD16a signaling is mediated by phosphorylation of Syk (pSyk).[50][51][52]

A study now suggests induced expression of CD32a upon activation of human CD4+ T cells, similar to CD16a.[51][53] CD32a expression on CD4+ T cells was also suggested by three independent studies from HIV-1 researchers. The expression of CD16a and CD32a in a subset of activated CD4+ T cells is now confirmed.[51][53] FcRs on the cell surface upon binding to ICs composed of nucleic acids trigger cytokine production and upregulate nucleic acid sensing pathways. FcRs are present both on the cell surface and in the cytosol. CD16a signaling upregulate the expression of nucleic acid sensing toll-like receptors and relocate them to cell surface.[50][54] CD16a is a new costimulatory signal for human CD4+ T cells, which successfully substitute the CD28 requirement during autoimmunity.[55] In an autoimmune background CD4+ T cells bypass the requirement of CD28 cosignaling to become fully activated.[55] Furthermore, the blockade of CD28 cosignaling does not inhibit the development of TFH cells, a key subset for the generation of autoantibody producing autoreactive plasma B cells.[56] A balance among costimulatory and inhibitory signals is required for immune homeostasis. Excessive costimulation and/or insufficient co-inhibition leads to the tolerance-breakdown and autoimmunity. CD16a mediated costimulation provides a positive signal in the activated CD4+ T cells and not in the quiescent cells which lack FcγR expression.[51]

See also

  • Fc receptor-like molecule

References

  1. ↑ "Manipulation of cell surface macromolecules by flaviviruses". Advances in Virus Research 59: 229–74. 2003. doi:10.1016/S0065-3527(03)59007-8. ISBN 9780120398591. PMID 14696331. 
  2. ↑ Owen, Judith; Punt, Jenni; Stranford, Sharon; Jones, Patricia (2009). Immunology (7th ed.). New York: W.H. Freeman and Company. p. 423. ISBN 978-14641-3784-6. 
  3. ↑ 3.0 3.1 3.2 3.3 "Fc receptors and immunoglobulin binding factors". FASEB Journal 5 (12): 2684–90. September 1991. doi:10.1096/fasebj.5.12.1916092. PMID 1916092. 
  4. ↑ "The molecular dissection of Fc gamma receptor mediated phagocytosis". Blood 86 (12): 4389–99. December 1995. doi:10.1182/blood.V86.12.4389.bloodjournal86124389. PMID 8541526. 
  5. ↑ "Binding of monomeric immunoglobulin G triggers Fc gamma RI-mediated endocytosis". The Journal of Biological Chemistry 269 (39): 24396–402. September 1994. doi:10.1016/S0021-9258(19)51097-3. PMID 7929100. 
  6. ↑ 6.0 6.1 6.2 6.3 "Glycans in the immune system and The Altered Glycan Theory of Autoimmunity: a critical review". Journal of Autoimmunity 57 (6): 1–13. February 2015. doi:10.1016/j.jaut.2014.12.002. PMID 25578468. 
  7. ↑ "MHC class I-related neonatal Fc receptor for IgG is functionally expressed in monocytes, intestinal macrophages, and dendritic cells". Journal of Immunology 166 (5): 3266–76. March 2001. doi:10.4049/jimmunol.166.5.3266. PMID 11207281. 
  8. ↑ "The MHC class I-related receptor, FcRn, plays an essential role in the maternofetal transfer of gamma-globulin in humans". International Immunology 13 (8): 993–1002. August 2001. doi:10.1093/intimm/13.8.993. PMID 11470769. 
  9. ↑ "New functions of the MHC class I-related Fc receptor, FcRn". Biochemical Society Transactions 25 (2): 481–6. May 1997. doi:10.1042/bst0250481. PMID 9191140. 
  10. ↑ 10.0 10.1 10.2 "The Fc receptor for IgA (FcalphaRI, CD89)". Immunology Letters 92 (1–2): 23–31. March 2004. doi:10.1016/j.imlet.2003.11.018. PMID 15081523. 
  11. ↑ "Molecular and functional characteristics of the Fcalpha/muR, a novel Fc receptor for IgM and IgA". Springer Seminars in Immunopathology 28 (4): 377–82. December 2006. doi:10.1007/s00281-006-0050-3. PMID 17061088. 
  12. ↑ "Molecular characteristics of IgA and IgM Fc binding to the Fcalpha/muR". Biochemical and Biophysical Research Communications 345 (1): 474–8. June 2006. doi:10.1016/j.bbrc.2006.04.084. PMID 16681999. https://tsukuba.repo.nii.ac.jp/?action=repository_action_common_download&item_id=17550&item_no=1&attribute_id=17&file_no=1. 
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  14. ↑ "5. IgE, mast cells, basophils, and eosinophils". The Journal of Allergy and Clinical Immunology 117 (2 Suppl Mini–Primer): S450-6. February 2006. doi:10.1016/j.jaci.2005.11.016. PMID 16455345. 
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  17. ↑ "FCMR Fc mu receptor [Homo sapiens (Human)] - Gene - NCBI". https://www.ncbi.nlm.nih.gov/gene/9214. 
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  19. ↑ "Role of the IgM Fc Receptor in Immunity and Tolerance". Frontiers in Immunology 10: 529. 2019. doi:10.3389/fimmu.2019.00529. PMID 30967868. 
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  21. ↑ "Divergent signal transduction pathways and effects on natural killer cell functions induced by interaction of Fc receptors with physiologic ligands or antireceptor antibodies". Natural Immunity 14 (3): 123–33. 1995. PMID 8832896. 
  22. ↑ "Expression, regulation and function of human Fc epsilon RII (CD23) antigen". Immunologic Research 11 (3–4): 260–72. 1992. doi:10.1007/BF02919132. PMID 1287120. 
  23. ↑ "Fc receptors and their interactions with immunoglobulins". Annual Review of Cell and Developmental Biology 12: 181–220. 1996. doi:10.1146/annurev.cellbio.12.1.181. PMID 8970726. https://authors.library.caltech.edu/980/1/BJOarcdb96.pdf. 
  24. ↑ 24.0 24.1 "The coordination of signaling during Fc receptor-mediated phagocytosis". Journal of Leukocyte Biology 76 (6): 1093–103. December 2004. doi:10.1189/jlb.0804439. PMID 15466916. 
  25. ↑ "Structure and function of natural-killer-cell receptors". Immunologic Research 27 (2–3): 539–48. 2003. doi:10.1385/IR:27:2-3:539. PMID 12857997. https://zenodo.org/record/1236303. 
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  28. ↑ "The effect of phosphatases SHP-1 and SHIP-1 on signaling by the ITIM- and ITAM-containing Fcgamma receptors FcgammaRIIB and FcgammaRIIA". Journal of Leukocyte Biology 73 (6): 823–9. June 2003. doi:10.1189/jlb.0902454. PMID 12773515. 
  29. ↑ "Inhibitory receptors abound?". Proceedings of the National Academy of Sciences of the United States of America 94 (12): 5993–5. June 1997. doi:10.1073/pnas.94.12.5993. PMID 9177155. Bibcode: 1997PNAS...94.5993C. 
  30. ↑ "Augmented humoral and anaphylactic responses in Fc gamma RII-deficient mice". Nature 379 (6563): 346–9. January 1996. doi:10.1038/379346a0. PMID 8552190. Bibcode: 1996Natur.379..346T. 
  31. ↑ "Inhibitory signaling by B cell Fc gamma RIIb". Current Opinion in Immunology 10 (3): 306–12. June 1998. doi:10.1016/s0952-7915(98)80169-6. PMID 9638367. 
  32. ↑ "Fcgamma receptor signaling in phagocytes". International Journal of Hematology 84 (3): 210–6. October 2006. doi:10.1532/IJH97.06140. PMID 17050193. 
  33. ↑ "Receptors for the Fc fragment of IgG on natural killer cells". Natural Immunity 12 (4–5): 218–34. 1993. PMID 8257828. 
  34. ↑ "Regulation of human natural cytotoxicity by IgG. IV. Association between binding of monomeric IgG to the Fc receptors on large granular lymphocytes and inhibition of natural killer (NK) cell activity". Cellular Immunology 147 (2): 397–410. April 1993. doi:10.1006/cimm.1993.1079. PMID 8453679. 
  35. ↑ "Regulation of mast cell activation through FcepsilonRI". Chemical Immunology and Allergy 87: 22–31. 2005. doi:10.1159/000087568. ISBN 3-8055-7948-9. PMID 16107760. 
  36. ↑ "Gene expression profiles for Fc epsilon RI, cytokines and chemokines upon Fc epsilon RI activation in human cultured mast cells derived from peripheral blood". Cytokine 16 (4): 143–52. November 2001. doi:10.1006/cyto.2001.0958. PMID 11792124. 
  37. ↑ "Mast cells". Physiological Reviews 77 (4): 1033–79. October 1997. doi:10.1152/physrev.1997.77.4.1033. PMID 9354811. 
  38. ↑ "Mechanism of the interaction mediating killing of Schistosoma mansoni by human eosinophils". The American Journal of Tropical Medicine and Hygiene 29 (5): 842–8. September 1980. doi:10.4269/ajtmh.1980.29.842. PMID 7435788. 
  39. ↑ "Eosinophils: from low- to high-affinity immunoglobulin E receptors". Allergy 50 (25 Suppl): 20–3. 1995. doi:10.1111/j.1398-9995.1995.tb04270.x. PMID 7677229. https://zenodo.org/record/1230625. 
  40. ↑ "High-affinity IgE receptor on eosinophils is involved in defence against parasites". Nature 367 (6459): 183–6. January 1994. doi:10.1038/367183a0. PMID 8114916. Bibcode: 1994Natur.367..183S. 
  41. ↑ "Fc-receptors on human T lymphocytes. I. Transition of Tgamma to Tmu cells". J Immunol 121 (4): 1540–1548. 1978. PMID 308968. 
  42. ↑ "Lymphocyte Fc receptors: the special case of T cells". Immunol. Today 14 (5): 227–31. May 1993. doi:10.1016/0167-5699(93)90168-K. PMID 8517922. 
  43. ↑ "Activation-dependent expression of low affinity IgG receptors Fc gamma RII(CD32) and Fc gamma RIII(CD16) in subpopulations of human T lymphocytes". Immunobiology 192 (5): 297–320. 1995. doi:10.1016/s0171-2985(11)80172-5. PMID 7649565. 
  44. ↑ "Functional analysis of two human T-cell subpopulations: help and suppression of B-cell responses by T cells bearing receptors for IgM or IgG". J Exp Med 146 (1): 184–200. 1977. doi:10.1084/jem.146.1.184. PMID 301544. 
  45. ↑ Chauhan AK, Moore TL (2011). "T cell activation by terminal complex of complement and immune complexes". The Journal of Biological Chemistry 286 (44): 38627–38637. doi:10.1074/jbc.M111.266809. PMID 21900254. 
  46. ↑ Chauhan AK, Moore TL (2011). "T cell activation by terminal complex of complement and immune complexes". The Journal of Biological Chemistry 286 (44): 38627–38637. doi:10.1074/jbc.M111.266809. PMID 21900254. 
  47. ↑ Sandor M, Lynch RG (1993). "Lymphocyte Fc receptors: the special case of T cells". Immunology Today 14 (5): 227–231. doi:10.1016/0167-5699(93)90168-K. PMID 8517922. 
  48. ↑ "Fcgamma receptors as regulators of immune responses". Nat. Rev. Immunol. 8 (1): 34–47. January 2008. doi:10.1038/nri2206. PMID 18064051. 
  49. ↑ 49.0 49.1 "Mouse and human FcR effector functions". Immunol. Rev. 268 (1): 25–51. November 2015. doi:10.1111/imr.12350. PMID 26497511. 
  50. ↑ 50.0 50.1 50.2 "FcγRIIIa-Syk Co-signal Modulates CD4+ T-cell Response and Up-regulates Toll-like Receptor (TLR) Expression". J. Biol. Chem. 291 (3): 1368–86. January 2016. doi:10.1074/jbc.M115.684795. PMID 26582197. 
  51. ↑ 51.0 51.1 51.2 51.3 "Induced expression of FcγRIIIa (CD16a) on CD4+ T cells triggers generation of IFN-γhigh subset". J. Biol. Chem. 290 (8): 5127–40. February 2015. doi:10.1074/jbc.M114.599266. PMID 25556651. 
  52. ↑ Chauhan AK, Moore TL (2012). "Immune complexes and late complement proteins trigger activation of Syk tyrosine kinase in human CD4(+) T cells". Clin Exp Immunol 167 (2): 235–245. doi:10.1111/j.1365-2249.2011.04505.x. PMID 22235999. 
  53. ↑ 53.0 53.1 "CD32 Ligation Promotes the Activation of CD4+ T Cells". Front Immunol 9: 2814. 2018. doi:10.3389/fimmu.2018.02814. PMID 30555482. 
  54. ↑ Chauhan AK (2017). "FcgammaRIIIa Signaling Modulates Endosomal TLR Responses in Human CD4+ T Cells". J Immunol 198 (12): 4596–4606. doi:10.4049/jimmunol.1601954. PMID 28500073. 
  55. ↑ 55.0 55.1 "Intrinsic and extrinsic control of peripheral T-cell tolerance by costimulatory molecules of the CD28/ B7 family". Immunol Rev 241 (1): 180–205. 2011. doi:10.1111/j.1600-065X.2011.01011.x. PMID 21488898. 
  56. ↑ "ICOS maintains the T follicular helper cell phenotype by down-regulating Kruppel-like factor 2". The Journal of Experimental Medicine 212 (2): 217–233. 2015. doi:10.1084/jem.20141432. PMID 25646266. 

Further reading

External links



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