Chapter 12 - Body Defences Flashcards
Immunity
-body’s ability to resist or eliminate harmful materials or abnormal cells
Immune System Functions
-defend against invading pathogens
-removed ‘worn-out’ cells
-identify and destroy abnormal cells
-amount appropriate immune response
Bacteria
-a target of immune system
-non-nucleated, single-celled microorganisms
-tissue damage and cause diseases by releasing enzymes
Viruses
-target of immune system
-have DNA or RNA
-cannot carry out metabolism or reproduce without a host cell
Skin
-first line/barrier of defence
-exposed to external environment
-physical barrier
-produce antimicrobial chemicals
Mucous Membranes
-first line/barrier of defence
-sticky secretions
Saliva
-help combat bacteria
-good bacteria convert nitrate to nitrite which is swallowed
-nitrite converted to nitric oxide and killed by bacteria
Lymphoid Tissues
-tonsils & adenoids
-provide protection against inhaled pathogens
-cilia trap debris in mucus that contains antibodies
Alveolar Macrophages
-scavenge air sacs in the lungs
Neutrophils (Leukocytes)
-highly mobile phagocytes
-engulf and destroy unwanted materials
Eosinophils (Leukocytes)
-secrete chemicals that fight parasites
-allergic reactions
Basophils (Leukocytes)
-release histamine and heparin
-allergic reactions
Monocytes (Leukocytes)
-transformed into macrophages (phagocytic specialists)
B Lymphocytes (Leukocytes)
-transformed into plasma cells
-secrete antibodies
T Lymphocytes (Leukocytes)
-cell-mediated immunity
-produced from lymphoid colonies in lymphoid tissues
Lymphoid Tissues
-tissues that produce, store, process lymphocytes
-resident macrophages remove microbes
Bone Marrow
-B cell maturation
-origin of all blood cells
Thymus
-T cell maturation
-secretes thymosin hormone
Spleen
-exchanges lymphocytes with the blood
Innate Immune Responses
-nonspecific, rapid, limited response
-first line of internal defence
-work immediately when exposed to threatening agent
-non-selectively defend against foreign invaders
-mark as foreign by recognizing molecular properties (sugars, lipids) rather than species
Elements of Innate Immune Response
-neutrophils
-macrophages
-plasma proteins
Adaptive Immune Response
-specifically targets foreign material
-body has taken time to prepare to attack
-ultimate weapon
Antibody-mediated Immunity
-part of the adaptive immune response
-production of antibodies by B-lymphocyte derivatives (plasma cells)
Cell-mediated Immunity
-part of adaptive immune response
-production of activated T-lymphocytes
-directly attack unwanted cells
Inflammation (Innate Immunity)
-nonspecific response to tissue injury and foreign invasion
-bring phagocytes and plasma proteins to invaded area
-destroy invaders
-remove debris
-prepare for healing
Natural Killer Cells (Innate Immunity)
-lyse viral-infected and cancer cells
Interferon (Innate Immunity)
-viral infections
Inflammation Steps
- Break in skin introduces bacteria, macrophages engulf pathogens while secreting cytokines and chemotaxins
- Mast cells release histamine
- Histamine dilates local vessels, cytokines cause neutrophils and monocytes to stick to vessel wall
- Chemotaxins attract neutrophils and monocytes which squeeze out of vessel wall and migrate to infection sites (diapedesis)
- Monocytes enlarge into macrophages which engulf and destroy pathogens
Chemotaxis
-chemicals released initiate rolling (margination) and migration
Diapedesis
-emigration of leukocytes
Phagocytosis
-recognize certain carbohydrates or lipids on bacterial wall after contact
-aided by opsonins (prepare for eating)
Pus
-collection of phagocytotic cells and dead tissues
Opsonins
-not the name of a specific chemical
-the action of agents to help phagocytosis
Histamine
-released from mast cells
-induces local vasodilation
-increases capillary permeability
Interleukin-1 and 6 (TNF)
-from macrophages
-induce fever and promote inflammation
-enhance proliferation and differentiation of B and T lymphocytes
Perfect Tissue Repair
-cell division replaces lost cells with same kind of cells
Non-regenerative Tissue Repair
-nerve and muscle tissue
-lost cells replaced with scar tissue
Complement System (Innate Immunity)
-plasma proteins attack cell membranes
-nonspecific response
-composed of plasma proteins
-produced by liver
-circulate in inactive form
Complement System Steps
-cascade sequence of events
-C1-C5 activate each other
-C5-C9 assemble to form the membrane attack complex (MAC)
Membrane Attack Complex (MAC)
-hole punch
-embed in membrane
-leaky membrane
-victim cell swells and bursts
-killing without phagocytosis
Complement System - Primary Mechanism
-activated by antibodies to kill foreign cells
-classical pathway
Alternative Pathways
-activated by exposure to carbohydrate chains on surface of microorganisms
Complement Proteins
-act as opsonins
-promote vasodilation and vascular permeability
-stimulate release of histamine
Antiviral Effect (interferon)
-inhibit virus multiplication
-trigger virus-blocking enzymes
-released nonspecifically
-provide general rapid defence
Natural Killer Cells
-naturally occurring lymphocyte like cells
-nonspecifically destroy infected cells
-lyse cell membranes upon first exposure
Antigen
-large, foreign, unique molecule
-induces an immune response
-more complex molecule = greater antigenicity
Surface Receptors
-each lymphocyte has
-bind with one particular antigen
Antibody Mediated Immunity (B Cells)
-bind with antigen
-differentiate into plasma and memory cells
Plasma Cells
-B cells that differentiate
-produce antibodies
-B cells have receptors, when an antigen binds, the cell activates and divides into Plasma cells
Memory Cells
-B cells that differentiate into dormant cells
-exposure to antigens wake up cell and start the immune response
-secondary response is quicker and longer lasting (induced by disease or vaccination)
Plasma Cells
-produce antibodies that combine with specific antigens
IgM (Immunoglobulin/antibody subclass)
-B cell surface receptor for antigen attachment
-secreted in early stages of plasma cell response
IgG (Immunoglobulin/antibody subclass)
-most abundant immunoglobulin in blood
-produced in large amounts when exposed to same antigen
Antibodies
-y shaped molecule
-four linked polypeptide chains
Tail of Antibody
-determine functional antibody properties
-constant region
-identical to subclasses
Tip of Antibody
-identical antigen binding fragments (Fab)
-on tip of each arm (unique to each antibody)
Antibodies in Action
- Neutralization: antibodies neutralize toxins
- Agglutination (clumping of antigenic cells) and Precipitation (if the soluble complex is too large for solution) - prevents escaping cells
- Compliment System is Activated: inactive C1 complement molecule is activated by binding with antigen + antibody
- Phagocytosis is enhanced (opsonization): phagocyte attaches to receptor
- Natural Killer cell stimulated
Clonal Selection
-diverse B lymphocytes (produced during fetal development) synthesize antibodies against particular antigens
Clone
-identical antibodies cells formed by offspring of ancestral B lymphocytes
-not acquired
-mature in thymus
Active Immunity
-self-generated
-results from exposure to antigen
Passive Immunity
-borrowed immunity
-results from transfer of preformed antibodies
-immediate protection
Preformed Antibodies
-natural or human intervention
-breastmilk
-grow and inject antibodies
T Lymphocytes
-defence against most viral infections
-regulatory role in immune mechanisms
-cell-mediated immunity
-directly bind to targets (don’t secrete antibodies)
Cytotoxic T Cells (aka CD8 or killer T cells)
-release chemical that destroy targeted cells that are infected with a virus (host cells)
-kill cell directly or through enzymes
-require class 1 MHC + antigen
Helper T Cells (CD4 cells)
-secrete chemicals that amplify activity of other immune cells
-not killer cells
-augment immune system
-secrete cytokines
-require class 2 MHC + antigen
Memory T Cells
-memory pool
-primary (lymphoid tissues) and secondary responses
Major Histocompatibility Complex (MHC)
-membrane bound glycoproteins
-individual uniqueness
Antigen Presentation
-allows T cells to recognize antigens on the surface of cells
Class 1 MHC Molecules
-expressed on surface of all nucleated cells
Class 2 MHC Molecules
-expressed on immune system cells
-macrophages, dendritic cells, activated B cells
Perforin Molecules
-release granzymes to induce apoptosis
-released virus is phagocytized
