The immunobiology of Fc receptors

Published on January 31, 2021   39 min

Other Talks in the Series: The Immune System - Key Concepts and Questions

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I'm Professor Mark Cragg. I'm a professor of experimental cancer biology at the Antibody and Vaccine Group in the Centre of Cancer Immunology in the University of Southampton. The talk that I'm going to give today is around the immunobiology of Fc receptors.
Fc receptors bind the Fc domain of antibodies. I'm sure you're all aware of the structure of an antibody. It's this Y-shaped molecule which has Fab domains which do the binding of the antibody, which bind to different epitopes and antigens, which carry the variable regions, whereas we also have the stem part of the antibody molecule, known as the Fc or fragment crystallizable. It's that fragment crystallizable, the Fc domain, which is bound by Fc receptors. Importantly, Fc receptors are able to bind to different classes of antibody. You can see that there are a number of different classes of antibody, IgA, D, E, G, and M, and each of them have different functions within the immune system. For example, IgA protects mucous membranes, whereas IgM is a key component of the primary immune response, and IgG of the secondary antibody response. But it's important to recognise that several of their key functions are actually mediated by Fc receptors.
In the mouse system, there are a whole host of Fc receptors that can bind to those different antibody molecules. There are a whole series which are isotype-specific. For example, a polyIgR is an Fc receptor which can bind to IgM molecules and also IgA molecules. In contrast, we have receptors such as Fc epsilon receptor I (FcεRI) and Fc epsilon receptor II (FcεRII), which bind only to IgE molecules. We also have a whole series of receptors which bind to the Fc gamma receptors, which bind to IgG, and I'm going to be spending a lot of time talking about those in the later slides. It's also important to say that there's an intracellular Fc receptor called TRIM21, which binds antibodies when they've been internalised (after they have bound to viruses for instance), and that stimulates an antiviral response. But we're not going to get into that particular Fc receptor in any great detail.