Biology- immune system

• Lymph nodes filter out bacteria and viruses from the lymph.
• Lymph is a clear fluid that contains white blood cells (lymphocytes) and other substances such as proteins and fats.
• 1. In the second line of defence the receptors on the macrophages detect the chemicals on the pathogen and move to it via chemotaxis
• 2. The macrophage then engulfs the pathogen via endocytosis and this means it is now a phagosome
• 3. The lysosome then enters the pathogen by the cytoskeletons and then it releases the hydrolyctic enzymes which destroys the pathogens cell wall, this is now a phagolysome
• 4. The antigen are then moved to the macrophanges cell surface membrane and makes a antigen-presenting cell
• The other 2nd line of defence is when a person gets cut and what happens is the mast cells break and realses histamine
• 2. The histamine makes the Capillaries more permeable so more macrophages can pass through, it also makes the arteroles more diastolic so more blood can flow through
• The three symptoms of a cut is red, inflammation, heat, pain
• the first stage of an allergic reaction is that the allergen binds with the antibody on the B cell and activates them
• The skin contains a tough physical barrier called keratin
• B-cells mature in the bone marrow and are involved in humoral response
• T cells move to the bone marrow to the thymus to mature and are involved in cell mediated response
• Cell mediated response- the antigen on the antigen-presenting cell is recognized by T cells
• Cell mediated response part2- T cells are activated by antigen presenting cells (APCs)this is clonal selection
• Cell mediated response 3-the t helper cells release cytokines which stimulate the production of antibodies by attracting more macrophages
• CMR part4: the t helper cell divided my mitosis, this is called clonal expansion
• CMR 5- the clonal expansion of t cytotoxic cells secrete perforin to destroy infected cells as it creates pores so it makes the membrane more permeable, killing the cell
• in humoral response a b-cells receptor binds to a complementary antigen on the pathogen and it then engulfs the pathogen by phagocytosis , and leaves the antigen in its cell surface membrane
• HR part 2-a T helper cell that has the same receptor as a b-cell can bind to the presented antigen, this activate T cell causing it to release cytokines which activates b- cells
• HR part 3- the b-cell undergoes mitosis to make b- plasma and B- memory cells
• HR part 4- the plasma cells make antibodies to destroy pathogen and b- memory cells can divide into plasma cells in re-infected with the same pathogen
• • Passive immunity-short lived immunity that is acquired through the transfer of antibodies from another individual
• Active immunity- long lasting immunity that is acquired through exposure to a pathogen to trigger an immune response
• Natural passive- babies receiving mothers antibodies through breast milk
• Artificial passive- injection of preformed antibodies e.g. anti venom or rabies vaccine
• Natural active- being infected by a communicable disease
• Artificial active- vaccinations
• In vaccines the antigens from dead pathogen are detected by t helper cells which activate b cells by clonal selection
• After a vaccination b plasma cells that manufacture monoclonal antibodies and b memory cells that trigger secondary response is produced
• In secondary response there is a rapid increase in the number of lymphocytes and antibodies and a higher con in blood so a quicker response
• Live attenuated vaccines contain live weakened viruses/bacteria that cannot cause disease
• Ethical issues of vaccines-can have side effects, some people may not choose to have a vaccination and it may not be available world wide
• HIV- human immunodeficiency virus
• AIDS-acquired immunodeficiency syndrome- is a disease caused by the human immunodeficiency virus (HIV)
• Monoclonal antibodies is found in pregnacy test as it binds to hCG in a women’s urine
• Phosphodiester bonds are formed between adjacent molecules
• Cells that identify non-self cells are lymphocytes
• Each cell has its own specific molecule on its surface cell membrane which acts as a marker to identify it for example, an antigen, so lymphocyte can recognise the cell by its antigen, which is a protein and has a 3-D structure which is unique
• because of molecules antigens, a lymphocyte can recognise it, for example, pathogens that have antigens cancer, cells or toxins