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Chapter 25 - Immunology
- from SECTION 2 - MOLECULAR PATHOLOGY
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- By Wolfgang Prinz, BSc (Hons), MBA, PhD, formerly senior lecturer in the Divisions of Medical Biochemistry and Physiology, University of the Witwatersrand, is now an honorary member of staff of the Division of Molecular Medicine and Haematology. His main research interest is monoclonal antibodies., Mieneke Smit van Dixhoorn, a senior lecturer in the Division of Immunology, University of the Witwatersrand. She graduated from Leiden University in 1998 with a PhD in experimental IgA nephropathy and her post-doctoral work has focused on gene expression in xeno-transplantation, resulting in 20 peer-reviewed publications. She is a former Friedland Fellow., Elizabeth Mayne, MB BCh is currently a registrar in the Division of Molecular Medicine and Haematology but knows secretly that all medicine is really just about immunology. In her spare time, she studies the history of the Ancient Near East and Psychology., Ahmed A Wadee, obtained his BSc (Hons) at the University of Toronto and has both masters and PhD degrees from the University of the Witwatersrand.
- Edited by Barry Mendelow, University of the Witwatersrand, Johannesburg, Michèle Ramsay, University of the Witwatersrand, Johannesburg, Nanthakumarn Chetty, University of the Witwatersrand, Johannesburg, Wendy Stevens, University of the Witwatersrand, Johannesburg
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- Book:
- Molecular Medicine for Clinicians
- Published by:
- Wits University Press
- Published online:
- 04 June 2019
- Print publication:
- 01 October 2008, pp 289-310
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- Chapter
- Export citation
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Summary
INTRODUCTION
Immunology can be defined as the study of the reactions of a host when foreign sub stances are introduced into the body. Foreign sub stances that induce immune responses are referred to as antigens and are usually infectious agents. However, antigens may also be harm less environmental substances, such as pollen, which could trigger a response in certain individuals.
Early studies in immunology concentrated largely on the body's ability to protect itself and com bat antigens. As knowledge of the field accumulated, the scope of immunology has broadened significantly to include the study of molecular mechanisms and the genetic basis for the immune response, recognition of the body's response to self-antigens in autoimmune diseases, the phenomenon of hypersensitivity and the manipulation of the immune system to suppress graft rejection and increase immune surveillance against cancerous cells. The defence systems are divided into two broad categories: innate immunity (representing non-specific defences) and adaptive immunity (specific defences).
INNATE IMMUNITY
The innate immune system works on the basis of pattern recognition of several highly con - served structures present on or in different micro-organisms. The innate system present in all classes of plants and animals provides an immediate defence, which is not long-lasting.
The most important line of defence in the body is the physical barrier which is provided by intact skin and mucosal surfaces. The physical barrier is supplemented by:
• Continuous movement, for example the movement of cilia in the respiratory tract
• Commensal bacteria, especially in the gastrointestinal tract (GIT)
• Secretion of antimicrobial substances such as surfactant in the lungs, lysozyme in tears and hydrochloric acid in the GIT.
Once a pathogen has penetrated these physical barriers, it is recognised as foreign. This relies on certain pattern recognition molecules, such as the toll-like receptors (TLRs). These surface receptors bind to a host of diverse microbial pro ducts including components of bacterial cellular membranes such as lipopolysaccharide (LPS) from Gram-negative cell walls and peptidogly cans from Gram-positive cell walls. Receptor binding results in intracellular signalling and the release of pro-inflammatory mediators.