immunology

• The nature of infection:

  • an organism replicating (the formation of biological viruses during the infection process in the target host cells)  inside the body, resulting in disease. Some organisms, including all viruses, some bacteria and some parasites, infect body cells. Others replicate in organs such as the gut, in the blood or the spaces between cells.
• -Disease means when a person has an illness that stops their normal body functions working properly.

  -Disease can be caused by infection. This is a disease that can spread between people.

  -Infectious diseases are divided into different categories on the basis of the type of pathogen (disease causing organism):

  •Bacterial diseases caused by bacteria

  •Viral diseases caused by viruses

  •Fungal diseases caused by fungi

  •Parasitic disease caused by parasites
• -Common vehicles: Contaminated food, water, blood, or other vehicles may spread pathogens. Microorganisms like E. coli and Salmonella enter the digestive system in this manner.
• -Airborne transmission: Pathogens can also spread when residue from evaporated droplets or dust particles containing microorganisms are suspended in air for long periods of time. Diseases spread by airborne transmission include measles
• -Vectors: Organisms such as fleas, mites, ticks, rats, snails, and dogs (vectors)can also transmit disease. The most common vector for human infection is the mosquito, which transmits malaria, West Nile virus, and yellow fever.
• Direct transmission includes:

  Physical contact, e.g. shaking hands

  Unprotected sexual contact

  Sharing needles

  Airborne particles breathed in, e.g. during a conversation. These can be droplets, such as water, or other particles such as dust or soot, that may have pathogens on them.

  Droplets spread by sneezes, coughs, or simply talking can transmit disease if they come in contact with mucous membranes of the eye, mouth, or nose of another person. E.g. tuberculosis and influenza are spread by airborne droplet transmission.
• indirect transmission includes;

  • vehicle transmission (taking in infected water or food) it is not direct because the food/water is acting as a vehicle for the pathogen
• antigens

  • every cell in the human body has markers to identify it
  • microorganisms(both pathogen and non-pathogen) have there unique markers
  • the markers are called antigen( which are macromolecules) and the allow cells to cell recognition
  • antigens are found on the cell surface membrane , bacterial cell wall or the surface of viruses
• • antigens are produced by the organisms own body cells and are know as self antigens
  • self antigens do not stimulate an immune response
  • non-self antigens stimulate a immune response
• non specific response

  non specific response is a generalized response to pathogen infection involving the use of several white blood cells and plasma protein
• eyes

  tears contain antibacterial enzymes lysosomes
• stomach

  acid to kill bacteria
• skin 


  provides a barrier, sweat contains antiseptic
• urine

  antibacterial properties
• ears 


  secrets was with antiseptic properties
• airway

  mucus secreting cells and ciliated cells help to trap and sweep away bacteria from the lungs
• inflammation 


  is a response of tissue to injury often injury caused by invading pathogens. it is characterized by increasing blood flow to the tissue causing increased temperature, redness, swelling and pain
• histamines

  is released by damages tissue causing vasodilation(widening of blood vessels which increase the flow of blood to the infected area and increase permeability of blood vessels
• inflammation

  • mas cells respond to inflammation and secret histamines
  • mast cells are a type of white blood cells that is found in the connective tissue all through the body especially under the skin, near blood vessels and lymph vessels , in nerves, and in the lungs and intestines
  • as a result of that antibodies, white blood cells ( phagocytes) and plasma leak our into the infected tissue and destroy the pathogen
• phagocytosis

  • this is where white blood cells call phagocytes
  • the phagocytes is attracted to the chemical signal on the pathogen
  • the pathogen binds to the surface of the phagocyte
  • the pathogen is then into the phagocyte within a vesicle called phagosome
  • it is digested by lysosome (enzyme) and destroyed
• b cells mature in the bone marrow and are involved in the humoral response
• t cells move from the bone marrow to the thymus gland where the mature, and are involves in the cell mediated response
• • antigen presenting cell (APC) is an immune cell that detects, engulf, and informs the adaptive immune response (specific immune response)about an infection
  • when a pathogen is detected, these APCs will phagocytose the pathogen and digest it to form different fragments of the antigen
  • antigen fragments will then be transported to the surface of the APC, where they will serve as an indicator to other immune cells
  • receptors on specific T cells fit exactly on to these antigens
  • this attachment activities the T cells to divide rapidly by mitosis and form clone of genetically identical cells
• helper T cells

  these co-operate with B cells (in antibody production) they also activate macrophages and inflammation.
• memory T cells 


  remain after the pathogen have been killed to stop re-infection(by storing data about the pathogens antigens)
• suppressor T cells

  these are basically are the off switch for the immune system, the come into play when the antigen have been dealt with
• killer T cells

  these combine with the antigen in the invading cell and release chemical (lymphokines) which kill the pathogen directly and some stimulate other lymphocytes to become active and can also increase inflammation (so there is more macrophages)
• humoral immune response

  -is associated with the b cells/lymphocyte where the roles of these cells is to identify the antigen or any foreign particles that prevent the circulation in blood or lymph

  -the immune response is also assisted with helper T cells which along with B cells get differentiated into plasma B cells that can produce antibodies
• plasma B cells 


  there are short lived cells whose main function is to produce a large amount of antibodies against a large a particular antigen. Their main function is during the infection itself, also known as the primary immune response
• memory B cells 


  are mainly involved in the secondary immune response, or the second time the body is infected by the same pathogen. memory B cells rapidly differentiate into plasma B cells in order to quickly produce antibodies against the pathogen. in doing so the second tine the infection occur, the body is able to fight it much more quickly and efficiently than the primary infection
• passive immunity 


  is provided when the person is given antibodies to a disease rather than producing then through his or her own immune system
• natural passive immunity 


  involves fetus or newborn receiving antibodies from the mother
• artificial passive immunity

  is acquired by the injection of antibodies from the blood of immune people or from non-human immune animals
• initial response to injury involves an inflammatory response which:

  • increases blood flow
  • increases metabolic rate
  • redness at the site of injury as a result of increased accumulation of fluid
  • swelling cause by increased accumulation of tissue fluid around the site of injury
• label this

  A) increase blood flow

  B) fluid releases into tissue

  C) extravasation of leukocytes to the site of injury

  D) fever and proliferation of leukocytes

  
• proliferation phase

  • tissue repair takes place. tissue repair is to remove damage tissue and toxin/waste product
  • clotting helps to reduce blood loss and prevents pathogens from entering. clotting also help to blind the edge of the wound together and creates scar tissue.
  • dead or damaged cells are removed by phagocytes in a process similar to the removal of pathogens
  • new tissue to replace damaged tissue. a cell called fibroblast replace the collagen lost by the injury
  • angiogenesis (growth of new blood vessels) meaning that the new tissue is supplied with blood and vessels
• • the maturing stage is the final stage of wound healing. there is a reduction in vascularisation and the scar beings to fade. the collagen laid down beings to form cross links which increase the tensile strength of the wound
  • tensile strength is a measure of the ability of the wound to resist pulling apart