unit 4 aos 1 revision immunity

self vs non-self antigens

self antigens are molecular markers on the surface produced by your own body, featuring your unique genetic sequence. immune system will typically recognise these as tolerable (known as self-tolerance)

non-self antigens are molecular markers originating outside of the body, where the immune system recognises as foreign.

how are antigens presented to initiate an immune response?

APCs such as dendritic cells and macrophages will travel to the lymph nodes and/or spleen (secondary lymphoid organs) once phagocytosed a pathogen or foreign substance, and present their specific antigen markers on an MHC-II marker found on the outer cell membrane. a helper t cell with a matching specific t cell receptor (TCR) with bind to the MHC-II marker on the APC.

If NK cells miss virally infected, mutated or cancerous cells, cytotoxic T cells will scan MHC-I markers to ensure they are presenting healthy self-antigens. If they present non-self antigens, or mutated self antigens, that match their specific TCR, then they will elicit an immune response (perforin and granzymes release by tc cell = apoptosis)

cellular pathogens

pathogens which can grow and reproduce independently.

• bacteria (e.g. tuberculosis, pneumonia)

• fungi (e.g. yeast, athletes foot)

• parasites (e.g. tapeworm, hookworms)

• protists (e.g. malaria, giardiasis)

non cellular pathogens

pathogens which cannot grow and replicate independently and require a host cell.

• virus (inject their genetic code into host cell to hijack cell machinery for mRNA and protein production) (e.g. influenza, HIV)

• prion (an abnormally folded protein lacking DNA or RNA, inducing normal functioning proteins to misfold into the infectious shape) (e.g. mad cow disease, cjd)

primary lymphoid tissue

lymphoid tissue which are the sites for T and B cell maturation and generation. Both T and B cells are produced in the bone marrow, and B cells will remain in the bone marrow and mature here. T cells will mature in the thymus.

secondary lymphoid tissue

spleen and lymph node, where naive T and B cells are situated ready to be activated by binding to a matching specific antigen to undergo clonal expansion and elicit an immune response.

role of th cells

coordinate the immune responses by releasing cytokines to activate other cells such as macrophages, naive b cells and naive tc cells.

role of tc cells

to find, target and eliminate the body’s infected cells using specific markers to assist them in finding specific antigens found on the infected cells they need to destroy.

natural passive vs active immunity

natural passive immunity refers to receiving antibodies from mother to child (e.g. placenta during pregnancy, or breastfeeding), while natural active immunity refers to the body’s own generated antibodies from being infected with a pathogen, (e.g. catching a cold)

artificial passive vs active immunity

artificial passive immunity refers to receiving antibodies from an artificial external source, such as injections (e.g. anti-tetanus, antivenom), while artificial active immunity refers to the body being introduced to a pathogen via vaccination to develop its own antibodies for that specific pathogen (e.g. Covid-19 vaccine).

outbreak

relates to an uncontrolled occurrence of an infectious disease in a small geographic location/region.

epidemic

uncontrolled spread of a disease within a geographic location

pandemic

uncontrolled spread of a disease that crosses borders (worldwide)

endemic

consistent occurrence of a disease in a certain region

monoclonal antobodies (mAbs)

lab-made proteins designed to mimic your body's natural immune system. They act as highly targeted guides that lock onto specific proteins or antigens on diseased cells, helping your immune system find, block, or destroy them. Typically used for cancer therapies or suppressing autoimmune diseases

how are mAbs made

an animal (typically a mouse) is injected with a specific antigen, to elicit an immune response in its body and produce specific antibodies for the given antigen. Then the mouse spleen is harvested to get the specialised b cells which contain the antibody. The b cells are then fused with myeloma cells (immortal cancerous b cells) to undergo division infinitely. These cells are screened to ensure only the true hybrid cells are kept, which are then cloned infinitely. Scientists will also ensure that mouse protein structures are replaced by human structures so they are not rejected by the patient’s body.

mAbs treating cancer

can be made to bind to specific tumour markers to elicit an immune response

mAbs treating autoimmunity diseases

can be made to block and neutralise cytokines to interrupt the transmission of their signals to cells and tissues.