Biology - AS- OCR- Fighting disease + health

the effect of disease, bacteria and toxins and the bodys defence against them, also the various diseases and there symptoms and causes.


1) ATTRACTION- phagocytic cell comes into contact wth a foreign body is marked by an antibody and attracted to the cell surface receptors

2) RECOGNITION/ATTATCHMENT - the foreign body will either directly attatch to the cell or its marked antibody will attatch to to cell surface receptors

3) ENDOCYTOSIS - pseudopodium takes place and the foreign body begins to be taken into the cell and engulfed by phagocyte membrane making a phagocytic vacuole within the cell.

4) FUSING - phagocytic vacuole fuses with lysosomes within the cell to form a secondary lysosome

4) KILLING/DIGESTION - hydrolytic enzymes in lysosomes are emptied into phagocytic vacuole and foreign body is digested

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NEUTROPHIL                                       MACROPHAGE

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  • 60% of all white blood cells
  • smaller than macophages
  • numbers increase rapidly (mitosis) during infection
  • move through capillary walls and circulate tissue
  • short life
  • chemotactic (respond to the production of hisamine by cells under attack from foreign bodies)
  • lobed nucleus
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  • Only 4% of white blood cells
  • Larger than Neutrophils
  • Few circulate blood
  • Mainly in organs such as lungs, kidneys, lymph nodes
  • Long lived
  • Initiate immune system response
  • Cell to cell recognition
  • Also known as 'monocyte' (when circulating blood)
  • Bean shaped nucleu
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globular proteins- "immunoglobulins".

chains are joined by disulphide bridges.

Antibodies can...

  • 1) mark foreign bodies by binding to there antigen (they can then bind to cell surface receptors)
  • 2) prevent foreign bodies from entering a cell
  • 3) immobilise bacteria by attaching to flagella
  • 4) agglultinate (gather together) by sticking together foreign bodies in a clump
  • 5) form membrane channels in bacteria cells allowing water to move in via osmosis and cell eventually bursts
  • 6) can neutralise toxins and make harmless.
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  • Lymphocytes are for the bodys specific immune response
  • Lymphocytes are smaller than phagocytes
  • Large nucleus that fills most of the cell
  • The two types are B and T lymphocyte cells.
  • Specific lymphocytes are specialised to respond to one antigen and therefore one type of infection.
  • T cells are the coordinators, and they stimulate B cells to divide and secrete antibodies into the blood
  • T cells then seek out and kill any of the body's own cells.
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B cells circulate between blood and lymph. Firstly, stem cells differentiate into B cells which then undergo maturation. During maturation specific genes code for specific antibodies- 10 million types of B cells each with different antibodies on there surface, each variety multiplies and forms 'clones'.


1) B cell comes into contact with the specific pathogen where its antibody binds to the pathogens antigen.

2)Once bound they differentiate and clone themselves by mitosis into PLASMA cells and MEMORY cells.

B PLASMA CELLS - clone themselves and release antibodies to locate and attatch to pathogen's antigens.

B MEMORY CELLS- remain in the lymph nodes

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T cells work differently to B cells. Though they are similar that they both clone themselves and differentiate, however are activated by binding to the antigen rather than via antibodies.


1) a body cell is invaded by the foreign body and the cell displays the pathogens antigens on its surface -antigenic presentation

2) T cells with the appropriate specific receptors bind to the antigens surface

3) The cell then differentiates into KILLER cells and HELPER cells and clone by mitosis. Some of each then differentiate and develop into MEMORY cells

T HELPER- Secrete cytokines which stimulate B Cell division and activate macrophages

T KILLER- Secrete perforins which punch holes in membranes of infected cell killing the cell along with pathogen.

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IMMUNITY- secondary immune response

ACTIVE IMMUNITY- the body has already encountered the antigen and therefore has an immunological memory (memory cells) so can defend the body alot quicker and effectively.

ARTIFICIAL IMMUNITY- Via vaccination containing attenuated (weak), dead or subcellular fragment (proteins from the pathogen) antigens. Or alternately an inactivated toxin or parts of the pathogens DNA. This then triggers a quicker immune response.

PASSIVE IMMUNITY- immunity conferred by antibodies from a source outside the individuals body (naturally/artificially passive) -e.g the placenta, mother to child.

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