12 Immunity Flashcards
what is the immune response?
a response to the presence of a foreign antigen involving the activation of lymphocytes and the production of antibodies
what is the definition of the primary defences?
mechanisms that have evolved to prevent the entry of pathogenic organisms
give some examples of barrier defences
skin
- keratinocytes prevent entry of pathogens
- blood clotting prevent entry of pathogens to blood
eye
- conjunctiva protected by lysozyme
airways
stomach
- mucus layer
- HCl to maintain optimum enzyme pH and destroying pathogens in food
vagina
- low pH
give some examples of inflammatory defences
tissue injury –> release of histamine
dilation and leaking of local arterioles
capillaries become more permeable
outline the process of phagocytosis
{phagocytes = neutrophils + macrophages}
pathogens release chemicals/damaged mammalian cells release cytokines
phagocyte moves down chemical concentration gradient towards pathogen via chemotaxis
pathogen is attached to receptors on CSM of phagocyte
phagocyte surrounds and engulfs the pathogen in a phagosome
lysosomes containing hydrolytic enzymes fuse with the phagosome creating a phagolysosome
enzymes break down and digest the pathogen
useful products absorbed; unwanted are exocytosed
antigens presented on CSM to alert T helper cells
where are T cells produced and matured?
produced in bone marrow
matured in thymus gland
where are B cells produced and matured?
produced AND matured in bone marrow
what is maturation of B and T cells?
addition of receptors
what are the four types of T cells?
helper
- detect antigens and secrete cytokines
- stimulates B lymphocytes to produce B plasma and memory cells in clonal selection and expansion
killer
- destroy infected cells by producing a protein that punches a hole in the CSM
regulatory
- supressor - maintain tolerance to self-antigens
- prevent AI diseases
memory
- remain and circulate in blood and tissues
- co-ordinate a response on reinfection
what is the function of B cells? what are the two types?
to search for the antigen that matches their receptors (clonal selection)
stimulated by T helper cells to divide in clonal expansion
plasma
- produce monoclonal antibodies which bind with the antigen to form an antigen-antibody complex, immobilising the antigen
memory
- recognise pathogens and co-ordinate more antibodies for response to secondary infection
what are antibodies?
soluble glycoproteins that bind to complementary antigens on the surface of the pathogen
where do antibodies come from?
B plasma cells
what is neutralisation?
antibodies combine with viruses/bacterial toxins to prevent them entering/damaging cells
what is agglutination?
antibodies immobilise pathogens by clumping them together to stop them entering the cell and making them easier to be phagocytosed
what is immobilisation?
antibodies stop movement of bacteria by attaching to flagella
what are lysis-antibodies?
antibodies that bind to foreign bodies and attract complement proteins which ‘punch’ pores in the CSM
what is opsonisation?
the constant region of the antibodies attaches to receptors on CSM on phagocyte
the variable region attaches to antigens on pathogen ∴ it can be engulfed
why is a secondary immune response more effective than primary immune response?
clonal selection and expansion takes a long time
differentiation of T/B cells takes time
production of antibodies by plasma cells
more memory cells @ secondary response
what is the Mantoux/tuberculin test used to diagnose?
tuberculosis
in the Mantoux test, how big must the induration be for a normal healthy person to have TB?
> 15 mm
in the Mantoux test, how big must the induration be for someone with a weakened immune system to have TB?
> 5 mm
what are the two ways in which we screen for HIV?
point of care
- finger prick/mouth swab
- results in 11 - 28 days
blood samples
- tests for both antigens and antibodies
- results in 11 - 28 days
outline the ELISA test
capture molecule is fixed to a surface
target antigens bind to a capture molecule
detecting antibodies added and bound
solution rinsed - non-captured detecting antibodies washed away –> negative result
if not, substrate added and bound
enzyme changes colour –> positive result
change in colour marked in optical density
antigen concentration x optical density plotted in calibration curve
what is hypersensitivity?
an undesirable reaction produced by the immune system
what is sensitisation?
initial contact with the allergen triggers the primary immune response
plasma cells produce ImmunoglobulinE antibodies, which bind to receptors on mast cells
how does exposure to an allergen cause an inflammatory response?
allergen binds to variable region on IgE on mast cells
stimulated to produce histamines
blood vessels vasodilate and ‘leak’ plasma
what is active immunity?
activation of B and T lymphocytes in response to the presence of pathogenic antigens, resulting in the production of antibodies and memory cells
what is the difference between natural and artificial active immunity?
natural = primary immune response to natural infection to a pathogen
artificial = deliberate introduction of antigens to stimulate primary immune response (i.e. vaccination)
what is passive immunity?
no activation of lymphocytes and no memory cells produced
presence of antibodies ONLY
what is the difference between natural and artificial passive immunity?
natural = e.g. from mother to foetus across placenta/breast milk
artificial = injection of antibodies from another source
