Disease and Immunity

Communicable- infectious diseases such as; Malaria, Influenza, Cholera, Tuberculosis, HIV/AIDS Non-communicable include diabetes, arthritis, lung cancer scurvy, emphysema not caused by pathogens and non-infectious. Lifestyles affecting human health- smoking, poor diet, lack of exercise, alcohol, stress A pathogen is a disease causing organism. Fungi- Eukaryotic e. g. athlete’s foot Bacteria- Prokaryotic e. g. TB Virus- Akaryotic e. g. HIV Pathogens can be transmitted by direct contact, airborne, waterborne, food, insects and animals Pathogens cause disease by producing toxins and damaging cells.

Cholera This is a serious water borne and food borne bacterial infection Sufferer suffers from dehydration and diarrhoea. A toxic protein is released by the cholera bacteria into the small intestine. Toxin damages the carrier proteins in the plasma membrane of the epithelial cells lining the small intestine. This produces a large release of chloride ions into the gut lumen. This decreases the water potential of the gut The water potential gradient causes the intestinal cells to lose large amounts of water into the gut lumen

Oral rehydration solutions contain sodium glucose and water. Increases uptake of sodium and glucose into the epithelial cells by making use of the sodium-glucose co-transport proteins. Lowers the water potential inside the cells Water following from the lumen by osmosis Ethical issues For- may be faster relief from symptoms, may benefit others later Against- may be less effective than previous, cost Defence against disease Lysosome enzyme in tear Cilia and mucus in trachea Sweat glands in skin Acidic pH of stomach Phagocytosis

There immune system is divided into non-specific and specific response. Non-specific- is always the same and is effective against a wide range of pathogens and substances considered non-self. Phagocytosis is the term used to describe how a phagocyte engulfs a foreign substance. 1. Phagocyte engulfs pathogens 2. They are enclosed in a vacuole 3. This vacuole fuses with lysosomes 4. Lysosomes contain hydrolytic enzymes 5. These hydrolyse the pathogen The phagocyte places antigens from the pathogen on its cell surface to become an antigen presenting cell, i.

e. let other cells know. The specific immune response is brought about by white blood cells called lymphocytes. The response is specific because each lymphocyte only recognises one antigen. An antigen is a protein on a cell membrane causing an immune response, involving antibodies. An antibody is a protein produced by a B cell in response to a particular antigen. It combines with the antigen forming an antigen-antibody complex and causes it to be destroyed. The cell mediated response 1. Pathogens invade body cells

2. Phagocyte places antigens from the pathogen on its surface 3. Receptors on certain specific T helper cells fit exactly into these antigens 4. T cells divide rapidly by mitosis to form clones 5. Cloned T cells; kill infected body cells, develop into memory cells for future infections The humoral response 1. Involves B cells and antibody production 2. The cell surfaces of B cells contains receptors which bind to non- self antigens 3. Specific lymphocyte with complementary receptor attaches to antigen 4.

Divides rapidly by mitosis to give a clone and identical lymphocytes. 5. Cloned cells become plasma cells which secrete antibodies that destroy pathogens 6. Or produce large numbers of memory for future encounters In this way they provide long term immunity against the original infection. Known as the secondary immune response and is more rapid and of greater intensity. Antigenic Variability Influenza viruses and some other viruses have lots of different strains.

The antigens on each strain are different and this is known as antigenic variability These will not correspond to the memory cells from previous infections and so the body reacts to the pathogen as a new infection and produces a primary response. Monoclonal antibodies Are of one type/ have the same structure and will therefore bind to one specific antigen. They are produced by one clones of one B-cell =. Antibodies that can be produced outside the body have great use. E. g. in immunoassay- calculates the amount of a substance in a mixture. Used in

pregnancy kits, testing for drugs and AIDS test. Ethical issues- involves using mice to produce antibodies by causing cancer in them For- benefits humans in future, new medicines/drugs to use, mice are in least possible state of suffering. Against- suffering in mice (animal cruelty), animals have no choice Vaccination A vaccine contains antigens and stimulates production of antibodies, plasma cells and memory cells Vaccination is the introduction of a weakened pathogen into the body with the intention of stimulating active immunity/ antibody production against a particular pathogen.

It can protect whole populations. For a vaccine to be successful enough of the population needs to be immunised- herd immunity. Problems with taking a vaccine orally: Could be broken down by enzymes in the gut Molecules may be too large to be absorbed into the blood Ethical issues regarding vaccines: Involves animal testing Should vaccines be compulsory? Can people opt out? On what grounds? In case of an epidemic who would get vaccinated first? Testing on human volunteers- vaccine may not work On whom should vaccine be carried out