Week 2: How the immune system combats viral infection
Introduction
During the COVID-19 pandemic, you will have heard a lot about antibodies and how vaccines induce neutralising antibodies that protect against infection. But antibodies are just one element of immune defence. Do you remember hearing about T cells and immunological memory? This week you will learn more about these and about the range of adaptive immune responses that combat viruses and deal with virus-infected cells.
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Transcript: Audio 1 Introduction to Week 2
DAVID MALE:
Adaptive immune responses are mediated by leukocytes, including lymphocytes, which come in various types – Cytotoxic T lymphocytes and Natural Killer cells, or NK cells, recognise and destroy virus-infected cells. B lymphocytes make antibodies which block virus binding to target cells and help macrophages, NK cells and the complement system to recognise a virus and virus antigens on infected cells.
Antibodies come in different classes, which have different roles in protection. IgA antibodies are particularly important in protecting mucosal surfaces against respiratory viruses.
The adaptive immune system displays immunological memory, which is the basis of vaccination – by immunising with a harmless antigen or attenuated pathogen, the immune system is primed to make a strong response if it subsequently encounters the real pathogen. Long term immunity resides in memory B and T cells, which persist, distributed throughout the body, even when antibody levels have declined.
Audio 1 Introduction to Week 2
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By the end of this week you should be able to:
- describe how T cells and NK cells recognise and destroy virus-infected cells
- outline how B cells recognise antigens and make antibodies
- list the major functions of different classes of antibody and their roles in combating a virus infection
- understand how innate and adaptive immune defences act in complementary ways
- understand the basis of immunological memory, which underpins vaccination.