This document provides a comprehensive overview of immunology, detailing the immune system's defense against pathogens. It explores the host-pathogen relationship, discusses key immunological terms, and outlines the innate and adaptive immune systems. The innate system, present from birth, is highl...
IMM Lecture 1: Introduction to Immunology
Primary function of the immune system – Defence against virulent pathogens
The Host - Pathogen Relationship
• Pathogen - Micro-organism with potential to cause disease
• Commensals - micro-organisms with which we co-exist and which are essential to our
wellbeing
• Opportunistic Pathogen (‘pathobiont’) - Normally not disease causing but becomes
pathogenic under certain conditions
Edward Jenner, smallpox and vaccination
smallpox disfigures and can be lethal.
Milk maids rarely got smallpox, but they did get cow pox blisters.
Birth of vaccinology - inoculation with cow pox pus protected from smallpox.
1796 Jenner: inoculation with Vaccinia à protection from smallpox
Vaccination prepares the immune system to eradicate an infectious agent before it causes
disease.
• Widespread vaccine use has saved many lives
• Classic examples: rabies vaccine and eradication of smallpox
Key Terms in Immunology
• Antibody – molecules that confer “anti-toxic” activity in serum.
• Antigens – substances that stimulate antibody generation.
• Leukocytes: “Leuko” = white (Greek) white blood cells
• Lymphocytes – a subset of leukocytes involved in adaptive immunity (from Lymph Node)
• Thymocytes – immature T lymphocytes in the thymus
• Humoral – of the “humors” or body fluids as opposed to Cellular.
• Cytokines – hormones for immune responses: lymphokines; interleukins; chemokines;
interferons
Where is the immune system?
Everywhere!
Made in the bone marrow.
Waiting in blood and tissues
Pathogens come in a variety of shapes and sizes and live both intra- and extra-cellularly.
Virus – 0.01-0.1um
Bacterial 1-10um
Protozoa 5-100um
Worms 5-5000mm
The immune system has evolved to deal with all these pathogens!
Recognises the presence of non-host entities.
Destroys and removes invaders
Vertebrates have two complementary systems.
1. Innate
Genetically programmed responses - we generally have the same components /
molecules.
Cellular components
Humoral
2. Adaptive
, Generation of a library of anti-microbial receptors
Adaptive and learning
Unique to you! - not genetically specified.
Cellular and humoral
The Innate Immune System
• Inbuilt immunity to resist infection
• Present from birth
• Not specific for any particular microbe
• Not enhanced by second exposure- i.e. Has no memory – (being
challenged currently)
• Uses cellular and humoral components.
• Is much less effective without adaptive immunity (in vertebrates).
Also involved in the triggering and amplification of adaptive immune
responses
A phylogenetically ancient system - in vertebrates and non-vertebrates, plants
• Essential for survival - A non-functional innate system is fatal.
• How does it work?
– Humoral factors (i.e. chemical weapons)
• Anti-microbial, e.g. reactive oxygen and nitrogen species; anti-
microbial peptides (AMPs)
• Blood clotting factors
• Chemo-attractants
• Inflammatory mediators
– Cellular
• Phagocytosis - ‘Cellular eating’
• Inflammation (increased blood supply)
Effectors of Innate Immunity
• Epithelial cells (barrier function, mucous secretion)
• Leukocytes (macrophages, granulocytes, NK cells, dendritic cells)
• Serum proteins (complement, soluble lectins, interferons)
• “Pro-inflammatory” Cytokines & Chemokines
First line of defence: Epithelial barriers
• Skin. Formidable barrier. Pathogen can only penetrate when
breached, e.g. wound, burns, insect bite.
• Mucosal epithelia (e.g. the gut, the airway) secrete mucus. Beating of
cilia causes mucus flow and thus expulsion of micro-organism.
Mucosal Immunity: structural barrier (innate immunity & adaptive immunity)
• Functions within seconds of contacting a pathogen.
• A mechanical, selectively permeable barrier between the ‘outside’
and ‘inside’
• Produce natural antibiotics - cationic antibacterial peptides.
• May possess motile cilia.
• Rapidly renewable
• Produce cytokines - proteins that influence the behaviour of other
immune cells.
• Produce chemokines - proteins that attract other cells.
• May produce mucins.
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