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Lymphocyte homing: getting lymphocytes to the right place at the right time

Published on October 29, 2020   62 min

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

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0:00
Hello, my name is Ann Ager. I'm a professor of immunology in the Division of Infection & Immunity at Cardiff University. Cardiff is the capital of Wales, which is part of the United Kingdom. Today I want to tell you about how lymphocytes move around our bodies in order to protect us mainly from infection. The title of my talk is Lymphocyte Homing, getting lymphocytes to the right place at the right time.
0:31
I'm going to start by giving a couple of slides just to introduce and give an overview of, a very short overview of how the immune system works, and then I'll talk about how lymphocyte homing fits into that. Then I'll talk about the relevance of this to controlling cancer growth and autoimmunity.
0:53
This is the problem as it were. How would you start off an immune response to an infection? Let's use influenza infection of the lungs. I'm sure a lot of you in the audience will be familiar with this virus infection and the effects it can have on our bodies. The frequency of naive lymphocytes with a receptor, for example, to influenza virus, is very low. We are born with a full complement of lymphocytes, but every Lymphocyte has a unique receptor and it's either T cell receptor on T cells or B cell receptor on B cells which recognizes a single epitope or an epitope in an and antigen. But the frequency is very low, only one in 100,000. So naive T-cells must survey the antigen-presenting cells, which presents the epitopes. In the case of T cells, this is a peptide MHC complex on the surface of the dendritic cell. Naive T cells must survey these antigen-presenting cells in order to engage peptide MHC to become activated to actually initiate either a T cell response, a cellular response or a B cell, a humoral or antibody-dependent immune response in order to clear infection. Naive B cells, like T cells, have the frequency of naive B cells, but this specific receptor is very low and they have to encounter activated T cells to initiate a T cell dependent antibody response, and by that I mean a class which response from IgM switch response to IgG, IgA and IgE. Lymphocyte homing solves this problem by bringing together naive T cells, naive B cells and antigen-presenting cells, and they all meet up with each other in the secondary lymphoid organs, ie, the lymph nodes and spleen.
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Lymphocyte homing: getting lymphocytes to the right place at the right time

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