Immunology Flashcards
Where do all immune cells originate?
bone marrow
Where do T cells mature?
thymus
What are polymorphonuclear leukocytes? Give the 3 classes.
immune cells that have granules containing enzymes that are released during immune response
neutrophils
eosinophils
basophils
Give the classes of mononuclear leukocytes
monocytes (differentiate to macrophages)
B cells (differentiate to plasma cells)
T cells (differentiate to T-regs, T-helper, cytotoxic)
What are the classes of T-helper cells?
Th1 and Th2
Where do B cells and T cells accumulate?
lymph nodes
What are dendritic cells?
antigen presenting cells in tissues
What is complement?
proteins that can be activated directly by pathogens or indirectly by pathogen-bound antibodies
Where is completed secreted?
liver
What are the 3 modes of action for complement?
direct lysis
attract more leukocytes to site of infection (chemotaxis)
coat invading organisms (opsonisation)
What creates hinge region on antibodies?
disulphide bonds
How does antibodies circulate?
in the blood, either:
free in plasma or
bound to B cells
What is the Fab region and what is its purpose?
antigen binding site of antibody
binds epitopes of antigen
When are Fab regions initially determined?
by a process called VDJ recombination during maturation in the bone marrow
What is avidity?
overall strength of binding between an antibody and an antigen
When is avidity increased?
avidity for antigen is increased during infection through somatic hypermutation in the germinal centres of secondary organs
What is the Fc region and what is its purpose?
fragment crystallisable region
area that binds Fc receptors on immune cell surfaces
also binds complement to aid in opsonisation of pathogens for phagocytosis
What are the functions of antibodies?
neutralisation of toxins
opsonisation of pathogens
complement activation via classical pathway
What are the two mechanisms of action of antibodies
direct attack on invaders or
activation of complement system
How do antibodies attack invaders directly?
- AGGLUTINATION: multiple large particles with antigens on their surface are bound together in a clump
- PRECIPITATION: the molecular complex of antibody and antigen (i.e. toxin) is so large it comes out of solution
- NEUTRALISATION: antibodies cover the toxic sites of the antigen
- LYSIS: some antibodies can attack the cell membrane directly and rupture
What are the 5 antibodies and where are they found?
IgG- most abundant serum antibody)
IgA- mucus secretions (secretory IgA), serum, coats neonate gut
IgM- too big to cross vascular endothelium so kept in blood
IgD- mature to form mIgD found on mature B cells
IgE- 50% in blood, rest bounds to mast cells and basophils
What is the function of IgG?
- main antibody in adaptive immunity (secondary/ memory responses)
- highly specific
- 4 subclasses
- can cross placenta
What is the function of IgA?
- first line of defence
What is the function of IgM?
- highest capacity to activate complement
- initial contact with antigen to form principle immune response
- 10 sites for antigen binding- very good at “mopping up” antigen in blood supply
What is the function of IgD?
no functions have been identified yet
What is the function of IgE?
- binds to basophils and mast cells
- antigen binding to IgE stimulates histamine release from basophils and mast cells
- hypersensitivity reactions
- defence against parasitic reactions
Whats the function of cytokines?
small proteins that are crucial in controlling the growth and activity of other immune system cells and blood cells
What are the main cytokines?
interferons
interleukins
colony stimulating factors
tumour necrosis factor
What do interferons do?
induce a state of viral resistance in uninfected cells and limit spread of viral infection
What are the three types of interferons and where are they produced?
produced by virus infected cells:
IFNapha
IFNbeta
produced by activated Th1 cells:
IFNgamma
What do interleukins do?
can be pro-inflammatory (IL1) or anti-inflammatory (IL10)
can cause cells to divide, to differentiate and to secrete factors
What do colony stimulating factors?
direct the division and differentiation on bone marrow stem cells (leukocyte precursor)
What are the type of tumour necrosis factor and what does it do?
TNFalpha and TNFbeta
mediate inflammation and cytotoxic reactions
