Phagocytic Cell Fc Receptors

Following interactions with the endothelium, the neutrophils express a number of specific receptors including Fc receptors for immunoglobulins (Table 1). Three classes of receptors are expressed by phagocytic cells: FcyRI (CD64), FcyRI (CD32), and FcyRIII (CD16). Most receptors are hetero-oligomeric complexes consisting of nine membrane-associated FcRs and three soluble FcryRs coded by eight genes. The receptors are transmembrane proteins with similarities to the BCR and TCR recognition proteins. Some receptors have "immu-noglobulin-like" domains. High-affinity FcyRI (CD64) contains three immu-

Tablet Cellular Receptors on the Surface ofPhagocytic Cells




CR1 (CD35)

Activated PMNs

C3b, iC3b, and C4

Follicular dendritic cells

CR2 (CD21)

Follicular dendritic cells

iC3b and C3dg

CR3, Mac-1, CDllb/CD18



Activated PMNs

Dendritic cells

FC7RI (CD64)


Human IgGl and IgG3

Activated PMNs

Mouse IgG2a

Oxidative burst

Fc^RII (CD32)


Polymeric IgG

Activated PMNs

Respiratory burst



IgG2a and IgG3

noglobulin-like domains in the extracellular region. FcyRII and FcyRIII have only two immunoglobulin domains and a lower binding affinity for IgG (Deo et al., 1997).

Genetic polymorphism among the Fc receptors is common. Alternate forms ofFcyRII (CD32) differby a single amino acid (arginine or histidine) at position 131 in the second Ig domain creating FcyRIIa-R131 or FcyRIa-H131(Fig. 1). The low-affinity receptor FcyRIIIalso has two alternate forms: FcryRIIIa and FcyRIIIb. Subtypes of both the FcyRIIIa and b receptors have been identified. The two allotypes of FcyRIIIa contain either valine or phenylalanine at position 158. Allotypes of FcyRIIIb-NAl or NA2 differ in five nucleotides that result in different glycosylation patterns (Deo et al., 1997)

How To Bolster Your Immune System

How To Bolster Your Immune System

All Natural Immune Boosters Proven To Fight Infection, Disease And More. Discover A Natural, Safe Effective Way To Boost Your Immune System Using Ingredients From Your Kitchen Cupboard. The only common sense, no holds barred guide to hit the market today no gimmicks, no pills, just old fashioned common sense remedies to cure colds, influenza, viral infections and more.

Get My Free Audio Book

Post a comment