The Immune Response Flashcards
What are the 6 features of the innate immune system?
- Natural skin flora prevents pathogenic bacteria colonising surface by outcompeting
- Skin and connective tissue is a barrier
- Localised inflammation localise breaks in the barrier
- Phagocytosis engulf pathogens
- Clothing prevents bleeding and entrance of pathogens into the wound
- Lysosome is an enzyme that kills bacteria eg in tears
- Ciliated epithelium have mucous membranes trapping microbes from inhaled air
What does adaptive mean?
The body produces a specific response to each antigen so the body is adapting. Lymphocytes provide this response, derived from stem cells in bone marrow.
Describe the humoral response.
Results in the production of antibodies. B lymphocytes mature in the spleen and lymph nodes the receptors on cell membranes respond to foreign protein and they divide making plasma cells releasing antibodies and memory cells which remain dormant and divide to form more B lymphocytes if the antigen comes again.
What are antibodies?
y shaped glycoproteins molecules called immunoglobulins. They have quaternary structure as each molecule is made of 4 polypeptides held by disulphide bonds. The variable portions are specific to each antigen. An antigen molecule binds to an antibody and each antibody molecule can bind to two antigen molecules. Microbes with antigens on their surfaces are clumped together ie they agglutinate.
Describe the cell mediated response.
Refers to the activation of phagocytic cells, B and T lymphocytes. T lymphocytes are activated in the thymus gland. The receptors on cell membranes respond to antigens and they divide, making T memory cells which remain dormant and divide to make more, t killer or cytotoxic T cells which kill pathogenic cells with the antigens by lysing them, and t helper cells which release chemicals like cytokines.
What do cytokines stimulate?
- phagocytic cells including macrophages, monocytes and neutrophils to engulf pathogens and destroy them
- B and T lymphocytes to undergo clinal expansion ie to divide rapidly into genetically identical cells forming a large population of cells specific to a particular antigen
- B lymphocytes to make antibodies
What is the primary immune response?
On the first exposure to an antigen there is a short latent period in which microphages engulf the foreign antigen or the cell/virus to which it is attached and incorporate antigenic molecules into their own cell membranes. This is antigen presentation. T helper cells detect these antigens and release cytokines. The b plasma cells secrete antibodies for about 3 weeks.
What is the secondary immune response?
Relies on memory cells. On reexposure to even a small amount of the antigen after a short latent period, memory cells undergo clinal expansion but faster than the primary response. Antibodies are made more quickly and are up to 100 times more concentrated. They remain at high concentration in circulation for longer and no symptoms develop.
What is active immunity?
The body makes its own antibodies in active immunity stimulated by either infection or vaccination. It is long lasting because it produces memory cells
What is a vaccination?
The cell mediated and humoral responses are initiated even though there is no harmful pathogen. Vaccines can be antigens isolated from the pathogen, weakened or ‘attenuated’ strains of the pathogen, inactive or killed pathogen or inactive toxin.
How do vaccines cause active immunity?
The vaccine is recognised by the body as being non-self and the immune system responds as if a pathogen was present. This is active as the body is making its own antibodies. Over time the number of memory cells decrease if the body isn’t exposed to the antigen again. So in some cases boosters are given to make more memory cells.
What is passive immunity?
The body receives antibodies produced by another individual. This can be from mother to foetus across the placenta or to baby in breast milk.
When are antibody injections/ig replacement therapy given?
- when rapid resistance is needed and there isn’t time for an active immune response to develop
- cases of primary immune deficiency disease and cases of acquired immunity conditions where patients don’t make enough antibodies so can’t provide enough protection.
Protection is short lived.
What makes a vaccination successfully protect?
The antigen must be highly immunogenic meaning a single dose would cause a strong response from the immune system. It would rapidly make a large number of antibody molecules
There should only be one antigenic type (serotype) of the pathogen.
Why is the flu A virus ineffective?
Flu a has many serotypes as it undergoes genetic recombination and frequent mutation. The memory cells may not be stimulated in a subsequent exposure due to mutation. A different vaccine would therefore be needed for each antigenic type.
