Week 6 - The innate response, the adaptive response Flashcards
What are the different types of pathogen?
DNA viruses, RNA viruses, bacteria, fungi, protozoa, worms
What are the main differences between innate and adaptive immunity?
innate - fast, non-specific, fixed
adaptive - slow, specific, responsive
Where are the complement proteins made?
in the liver
Where are complement proteins found?
blood, lymph and extracellular fluid
What is the function of the complement system?
to mark out a pathogen that has penetrated the epithelial barrier by coating it with complement proteins that makes them more easily phagocytosed
What are the inactive forms of the complement system called?
zymogens (infection triggers complement activation)
What is the most important complement protein?
C3
a deficiency in C3 can lead to successive severe infections
the end result of complement activation is the cleavage of C3 into C3a and C3b
What is the function of C3b?
attaches to the surface of a pathogen (complement fixation)
tags the pathogen for destruction by phagocytes
What is the function of C3a?
to act as a chemoattractant to recruit effector cells to the site of infection (anaphylatoxin)
What pathway works at the start of infection?
alternative pathway
What are the three pathways of complement activation?
alternative, lectin and classical
What are the four main outcomes the the complement system?
opsonisation, cell lysis, recruitment of inflammatory cells, clearence of immune complexes
What triggers the classical pathway of complement activation?
C-reactive protein or antibody binding to specific antigen on surface of pathogen
What triggers the lectin pathway?
mannose-binding lectin binds to pathogen surface
What receptor on the macrophage binds to C3b?
CR1 (complement receptor 1)
What is the function of C5b?
to initiate the formation of the membrane-attack complex
What antibodies activate the classical pathway?
IgG and IgM
What pathways provide antibody independant ‘innate’ immunity?
alternative and lectin
What is opsonisation?
a process in which bacteria and other cells are made available for phagocytosis
What are immune complexes?
insoluble lattices of antigen bound to antibody that trigger inflammation
How can immune complexes be cleared?
activated C3 can interupt the lattice making them soluble
C3 and C4 bind to CR1 on erythrocytes which transport the immune complex to the liver and spllen to be phagocytosed
What complement components from the membrane-attack complex?
C5 - C9
How is the complement system regulated?
by 8 complement inhibitors
CD59 - prevents formation of MAC by locking into it as it forms
What cell produces antibodies?
effector B lymphocytes (plasma cells)
What stimulates a B cell to proliferate and differentiate into a plasma cell?
the binding of an antigen to an immunoglobulinon its membrane
What are the five classes of immunoglobulin?
IgA, IgD, IgE, IgG and IgM
What is the most abundant antibody found in blood and lymph?
IgG
What is the structure of an antibody?
four polypeptide chains
two identical heavy chains and two identical light chains
What antibody is transferred to a newborn baby via breast milk?
This is an example of what type of immunity?
IgA
passive
What antibody is transferred to the foetus through the placenta?
IgG
another example of passive immunity where active immunity is transferred in the form of ready made antibodies
What is the function of peptidases?
to digest proteins
hydrolyse oligopeptides to aminoacids
Where are peptidases found?
on the brush border
What are the fat soluble vitamins?
A, D, E, K
What antibody do B lymphocytes secrete when they are first activated?
IgM - larger surface area
