Receptors for IgA on phagocytic cells

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Immunoglobulin A (IgA) receptors are present on various immune cells, including monocytes, polymorphonuclear neutrophils (PMNs), and eosinophils, particularly at mucosal surfaces.
• These receptors bind both secretory and serum IgA, utilizing the Ca2 region of IgA for ligand recognition.
• Expression of IgA receptors on monocytes and PMNs can be modulated by cytokines and lipopolysaccharides.

Purpose of the Study:

• To characterize the IgA receptor, its binding properties, and its functional role in immune responses.
• To elucidate the molecular structure and signaling pathways initiated by IgA receptor ligation.

Main Methods:

• Detection and characterization of IgA receptors on phagocytic cells.
• Analysis of IgA receptor binding specificity and molecular weight.
• cDNA sequencing to determine the receptor's predicted structure.
• Investigation of cellular responses upon IgA receptor ligation.

Main Results:

• IgA receptors bind secretory and serum IgA via the Ca2 region.
• Receptor expression is modulated by cytokines and lipopolysaccharides.
• Purified IgA receptors are heavily glycosylated (60 kD), with core protein of 32-36 kD.
• cDNA predicts a two-Ig-like extracellular domain structure with a transmembrane region and a 41-residue cytoplasmic tail.
• IgA receptor ligation triggers superoxide generation, inflammatory mediator release, phagocytosis, and microbial killing.

Conclusions:

• IgA receptors amplify the protective functions of IgA antibodies.
• These receptors play a significant role in mucosal defense mechanisms against pathogens.