Immunology 3.1.1.

Antibody Antigen An antigen stimulates an immune response from a specific antibody Antibody can only take part in an immune response if the correct antigen presents itself

Pathogens A micro organism that is capable of causing infectious disease - bacteria - fungi - virus Once inside the cells a pathogen releases toxins

FIRST LINE OF DEFENSE Physical barriers = first line of defence - non specific - response to pathogens always the same - immediate response - skin, mucosal surfaces, digestive system, blood - phagocytosis

SECOND LINE OF DEFENSE Immune system = second line of defence - highly specific - slower response - more powerful and effective - provides memory - white blood cells = lymphocytes, cell mediated = T cells and humoral – B cells

Inflammation First sign of an immune response - ‘Alarm chemicals’ released - blood vessels enlarge and capillaries become ‘leaky’ this allows white blood cells to pass move freely - Redness, swelling, heat and pain all caused by extra blood carrying immune systems cells Alarm chemicals signal further immune response from white blood cells

Phagocytosis Second stage of immune response Neutrophils and macrophages - squeeze through the capillary wall to access the infected tissue - attracted to the pathogen via chemotaxis (cells move down the concentration gradient)

Phagocytosis Chemotaxis = the bacteria is attracted to the phagocyte 2. Ingestion = Phagocyte begins to engulf the bacteria 3. Phagososome = Phagocyte surrounds the bacteria in a vesicle known as a phagosome 4. Phagolysosome = Lysosomes inside the phagocyte, containing digestive material is attracted towards the phagosome and fuse together 5. Digestion = Digestive enzymes break down the bacteria via hydrolysis reaction 6. Bacteria is destroyed, residual body is formed containing indigestible material Discharge = waste materials are pushed out of the body Phagocyte presents antigen markers on its surface to trigger an antibody response

When you get pus and goo from a wound, it’s the removal of dead neutrophils presenting there digested material as waste

Third line of defence Lymphocytes = T cells and B cells Both created in the bone marrow - T cells mature in the thymus gland - B cells mature in the bone marrow Both circulate in the blood looking for foreign antigens Both stimulated by complementary shaped receptors, causing clonal selection (enlarge and divide)

Cell mediated response T cells - Killer T cells: combine with antigens and release powerful chemicals (lymphokines) that can directly kill pathogens - Helper T cells: Co-operative with B cells in antibody production. They also promote further inflammation and phagocytosis - Memory T cells: Remain in the blood system after pathogens have been killed to prevent re-infection

Humoral response B cells: differentiate into mostly plasma cells and some memory cells (prevent re-infection) Remember they don’t leave the bone marrow, but produce antibodies which can travel in the blood to the infected site Complementary shape to fit the antigens as this shape initiated clonal selection in the first place

Antibodies Attach to antigens and ‘tag’ the pathogen, making it more visible to other cells (killer T and phagocytes) = neutralisation Many antibodies-antigen complexes join together creating a ‘clump’ of easily recognisable pathogens = agglutination

Immunological memory Plasma cells and T cells die after a few days Memory B cells and Memory T cells survive Each memory cell can only recognise the specific antigen already defeated Upon secondary infection an immune response is quicker and more powerful

Monoclonal antibodies Antibodies specifically targeted To treat disease e.g. cancer Animal is injected with disease and an immune response is triggered Antibodies are collected and grown in vitro Drugs can be attached to the antibodies making them more effective They can then be injected into humans

Artificial immunity Vaccines Injecting small artificially weakened pathogens into the body to allow an immune response Do not say ‘safe dose’ Memory cells are created If real disease is encountered, immunological memory exists and the body is ready to fight off the disease

Natural immunity Pathogen in encountered naturally Natural activation of the immune system involving T cells and B cells Natural immunological memory

Passive immunity Breast feeding Placental transfer Injection of cells from another person/animal Short term immunity B cells and T cells are non activated Memory cells are not created

Active immunity Trigger of immune response Cell mediated Memory cells created

Natural immunity Artificial immunity Active immunity Cell mediated immune response involving B cells, T cells and antibodies as a result of infection. Memory cells are created. Cell mediated immune response triggered by a vaccination. Involves B cells and T cells , Memory cells created Passive immunity Antibodies passed on from mother to baby through breast feeding, and mother to foetus through placenta. Short lived immunity with no memory cells created. Monoclonal antibodies passed on from an animal or human. Short lived immunity which no memory cells created.