Communicable diseases

• Airborne transmission occurs when pathogens are spread through droplets or dust particles in the air.
• The immune system of the body is highly complex, with white blood cells being the main component.
• The phagocyte surrounds the pathogen and releases enzymes to digest and break it down to destroy it.
• Once a pathogen has entered the body, the role of the immune system is to prevent the infectious organism from reproducing and to destroy it.
• Phagocytosis is a process where phagocytes engulf and digest pathogens, which can be non-specific or helped by antibodies which cause agglutination of pathogens.
• Production of antibodies and antitoxins are examples of immune responses.
• • The human body has a number of mechanisms that are the first line of defence against an infection
  • The non-specific defence systems of the human body against pathogens include:
  • The skin
  • The nose
  • The trachea and bronchi
  • The stomach
• Production of antibodies

  • Lymphocytes produce antibodies
  • Antibodies are Y-shaped proteins – each individual has the potential to make millions of different types of antibodies, each with a slightly different shape
  • The aim of antibody production is to produce the antibody that is specific(complementary) to the antigens on the surface of the pathogen
  • This is a specific type of immune response as the antibodies produced are specific to each pathogen's antigens
• It can take a few days to make the antibodies that are specific to a pathogen, giving the pathogen causing the infection enough time to make you feel unwell as its numbers in the body and the damage caused by them increase.
• Memory cells are lymphocytes that remain in the body after an initial infection with a particular pathogen, producing the specific antibodies against its antigens so that if you get infected by the same pathogen again in the future, the antibodies can be produced much quicker before the pathogen's numbers increase and it can cause damage to the tissues of the body.
• Some pathogens, usually bacteria, can produce substances which act as toxins that make you feel unwell.
• Lymphocytes can produce antibodies against these substances, which are called antitoxins.
• The antitoxins neutralise the effects of the toxin.
• Complement System - A series of proteins found in plasma that work alongside antibodies to kill bacteria and viruses. Complements form pores in the cell membrane of the pathogen leading to its destruction.
• Opsonisation - The antibodies attach themselves to the pathogen making it more visible to white blood cells called phagocytes. Phagocytes then engulf and destroy the pathogen through a process known as phagocytosis.
• Agglutination - Antibodies bind to the antigen on the surface of the pathogen causing them to clump together (agglutinate). This makes it easier for other cells to recognise and attack the pathogen.
• Phagocytosis is when white blood cells engulf and destroy invading microorganisms using their receptors on their surface.
• Macrophages are large phagocytes that patrol the body looking for foreign material such as dead or damaged tissue, debris from worn out red blood cells and pathogens.
• Antigens are molecules or structures present on the surface of microorganisms that trigger an immune response by the body's defence system.
• Macrophages are large white blood cells that engulf dead or dying cells and foreign particles such as bacteria.
• Antibodies are produced by B lymphocytes in response to specific antigens.
• Antibody-dependent cellular cytotoxicity (ADCC) - Antibodies bind to receptors on the surface of immune cells such as natural killer cells or macrophages. These immune cells recognise the bound antibodies and attack the pathogen.
• Immune memory is when B and T lymphocytes remember how to respond to a previous infection. This means they can quickly mount an effective response upon exposure to the same pathogen at a later date.
• Neutrophils are short-lived white blood cells that engulf and digest bacteria.
• The innate immune system provides immediate protection against infection without prior exposure to the pathogen.
• Active immunity occurs when your own immune system produces antibodies and memory cells following contact with a pathogen.
• Neutrophils are short-lived phagocytes which rapidly respond to infection by moving towards the site of inflammation where they can engulf and digest pathogens.
• Basophils release histamine during allergic reactions which causes vasodilation and increased permeability of capillaries allowing fluid to leak into tissues resulting in swelling.
• The complement system consists of proteins produced by the liver which work with antibodies to kill pathogens directly or mark them for destruction by phagocytes.
• Innate immunity includes physical barriers like skin and mucous membranes, chemical defences like acidity of stomach contents, enzymes in tears and saliva, and inflammation caused by histamine release.
• Adaptive immunity involves specific responses to particular pathogens and develops over time with repeated exposures.
• Bacteria can be killed through phagocytosis by macrophages.
• The complement system involves proteins called complement factors which work with antibodies to kill pathogens.
• Complement proteins can cause lysis (bursting) of bacterial cell walls.
• Complement proteins also attract neutrophils to the site of infection.
• Complement factors attach themselves to the surface of the pathogen making it more visible to phagocytes.
• The complement cascade involves three stages: activation, amplification and effector functions.
• The adaptive immune system consists of two main types of responses; humoral immunity and cell mediated immunity.
• Natural Killer Cells are white blood cells that destroy infected cells, cancerous cells, and virus-infected cells.
• Activation stage: Complement proteins are activated by binding to antibodies attached to the surface of a pathogen.