cell recognition and the immune system.

• Antibodies are proteins that are specific to antigen which they bind to
• antibodies are specific to an antigen as they have a complimentary shape
• antibodies bind to antigens to form a antigen-antibody complex
• antibody Quaternary structure :

  • made up of multiple amino acid chains ( as its a protein) connected by disulphide bridges
  • has some constant regions that bind to receptor on immune cells
• antibody tertiary structure ( unique )

  • two variable regions which are the antibody’s binding site
• agglutination : antibodies cause microbes to clump together making it easier for phagocytes to engulf more of them at once.
• antibodies can neutralise toxins
• antibodies can bind to viruses and stop them attacking to their host cells
• antigenic variability is how influenza viruses change over time
• Antigenic drift : smaller changes in viral surface proteins accumulate gradually , allowing the virus to escape immune recognition
• there are two antigenic variabilities :

  • antigenic shift
  • antigenic drift
• Antigenic variability is the ability of influenza viruses to change their surface proteins over time , hindering immune recognition
• antigenic shift : when influenza viruses from different animals combine together to create a new strand the immune system cannot recognize
• Immunity - when the body's immune system can kill a pathogen before it can cause any harm due to cell memory
• Lymphocyte is a type of white blood cell (immune response: )
• two types of lymphocytes:

  • cell-mediated responses involving T lymphocytes
  • humoral responses involving B lymphocytes
• lymphocytes distinguish the body's own cells as self and those that are foreign as non-self
• If lymphocytes could not distinguish self and non-self cells , they would destroy the organisms own tissues
• each type of cell have specific surface molecules that identify it
• proteins are the most important specific surface molecules as they have an enormous variety and a highly specific tertiary structure
• apoptosis - any lymphocytes that show an immune response to these self-antigens undergo programmed cell death
• two types of white blood cell : phagocytes and lymphocytes
• phagocytes ingest and destroy pathogens through phagocytosis
• lymphocytes are involved in immune responses
• phagocytes are attracted to the chemical products and damaged abnormal cells of pathogens , causing them to move towards the pathogens
• phagocytes have several receptors on their cell surface membrane that recognise and attach to chemical on the surface of the pathogen
• phagocytes engulf the pathogen to form a vesicle called a phagosome
• lysosomes move towards the phagosome and fuses with it
• enzymes called lysozymes are present in the lysosome
• lysozymes destroy the ingested bacteria by hydrolysis of their cell walls , the soluble products of the pathogen are then absorbed into the cytoplasm of the phagocyte
• antigens are a protein that are is any part of an organism or substance that is recognised as non-self by the immune system and stimulates an immune response
• the presence of an antigen triggers the production of an antibody as part of the body's defence system
• phagocytosis is a non-specific response as it occurs whatever the infection
• specific responses react to specific antigens , are slower in action but they provide long-term immunity
• specific immune response depends on a type of white blood cell called a lymphocyte
• lymphocytes are produced by stem cells in the bone marrow
• B lymphocytes mature in the bow marrow
• B lymphocytes are associated with humoural immunity
• Humoural immunity involves antibodies that are present in body fluids or ' humour ' such as blood plasma
• T lymphocytes mature in the thymus gland