Diseases and immunity

Diseases and immunity

LO:Define the key words: PathogenTransmissible diseaseActive immunityPassive immunityExplain the process of vaccinationExplain the specificity of antigensState the types of body defence

Pathogen = Disease causing organism

Transmissible diseaseIs a disease in which the pathogen can be passed from one host to another

Diseases can be transmitted:direct contact, e.g. through blood or other body fluids,indirectly, e.g. from contaminated surfaces or food, from animals, or from the air

Defence systemsMechanical barriers:- skin and hairs in the noseChemical barriers:mucus and stomach acidCells:phagocytosis and antibody production by white blood cells

can be enhanced by vaccination

Discuss the importance of:

hygienic food preparation, good personal hygiene, waste disposal and sewage treatment

in controlling the spread of disease

White blood cells: phagocytes, lymphocytesDistinguish between self and non-self cellsProduce antibodies

Molecules on the surfaces of cells that are not found in other organisms = antigens (e.g. blood system)

The response of lymphocytes to the presence of a foreign antigen = immune response

LymphocytesProduce antibodies; memory cellsantibodies lock on to antigens leading to direct destruction of pathogens, or marking of pathogens for destruction by phagocyteseach pathogen has its own antigens, which have specific shapes, so specific antibodies which fit the specific shapes of the antigens are neededPhagocytesphagocytosis

Memory cellsRemain circulating in the body for a long timeIf the same antigen is reintroduced a few weeks or months later, memory cells divide rapidly and develop into plasma cellsBasis of immunological memoryLast for many year, lifelong,

Phagocytosis

Immunity

Active immunitydefence against a pathogen by antibody production in the body is gained after an infection by a pathogen, or by vaccination

Passive immunityshort-term defence against a pathogen by antibodies acquired from another individual, e.g. mother to infantNo memory cells are producedImportant for new-borns: get all antibodies from the mother

Vaccinationprocess of vaccination:harmless pathogen given which has antigensantigens trigger an immune response by lymphocytes which produce antibodiesmemory cells are produced that give long-term immunity

Autoimmune diseases some diseases are caused by the immune system targeting and destroying body cellsType 1 diabetes