3.2.5 The Defensive Functions of Mammalian Blood Flashcards Preview

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Flashcards in 3.2.5 The Defensive Functions of Mammalian Blood Deck (55)
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 What is an antigen?

Molecules (usually proteins) that stimulates an immune response when detected by body


Describe how lymphocytes recognise self from non-self

  1. Each lymphocyte recognises a different chemical shape
  2. They collide with body’s own material (self)
  3. Some lymphocytes have receptors that fit body’s cells
    1. These either die or are suppressed
    2. Remaining fit only foreign material


Name the 4 main stages of immune response

  1. Phagocytosis
  2. Phagocytes Activate T-cells
  3. T-cells Activate B-cells, which divide into Plasma cells
  4. Plasma cells make more Antibodies to a Specific Antigen


Where are phagocytes found?

In blood and tissues


Describe phagocytosis (5)

  1. Phagocyte recognises (foreign) antigen
  2. Phagocyte engulfs pathogen
  3. Enclosed in vacuole/phagosome
  4. (Vacuole) fuses with lysosome
  5. Lysosome contains enzymes (lysozymes) that hydrolyse pathogen


Why does phagocytes moves towards pathogens?

∵ they're attracted to pathogen's chemical products


Phagocytes engulf pathogens by _____



Waste products removed by _____



How do lysozymes break down bacteria?

Hydrolyse the cell walls of bacteria


What do phagocytes do at the end of phagocytosis?

Phagocyte presents pathogen's antigens on its surface to activate other immune system cells


What do T-cells only respond to?

Antigen-presenting cells


Where do T-cells (aka T-lymphocyte) mature?

In thymus gland 


Describe what T-cells do

  1. Respond to antigens on foreign and infected cells
  2. Specific receptors on helper T cells bind to specific antigen presented by phagocytes (antigen-presenting cell)
  3. This activates T-cell: Binding triggers rapid mitosis = T cells are cloned


Name 4 things that the cloned helper T-cells do

  • Activate cytotoxic T cells 
  • Activate B-cells to divide and secrete their antibodies
  • Develop into memory cells 
  • Release chemical signals that activate and stimulate phagocytes


Describe how cytotoxic T-cells kill infected cells

  1. Produce protein called perforin that makes holes in cell-surface membrane
  2. Holes means cell membrane becomes freely permeable
  3. Control of substances no longer controls and cell dies


Why is the action of T-cells most effective against viruses?

∵ they replicate inside cells, sacrificing these body cells prevents viruses from multiplying and infecting more cells


What is the role of macrophages in stimulating B lymphocytes?

  • Antigen in membrane presented to lymphocytes
  • Produce cytokinins


What are B-cells (B-lymphocytes)?

White blood cell that's covered with antibodies


What are antibodies?

  • Proteins that bind antigens to form antigen-antibody complex
    • Stimulate immune response


Describe how T-cells activate B-cells, which divide into plasma cells

  1. When antibody on surface of B-cells meets complementary shaped antigen = binds to it
  2. This, together with chemicals released from helper T-cells, activates B-cell = divides by mitosis
  3. Clonal selection: form clones/produce plasma cells
  4. Make antibodies 
  5. Plasma cells produce memory cells


What do plasma cells do?

Secrete loads of antibodies specific to antigen

callled monoclonal antibodies


Describe what antibodies do to destroy pathogens

  1. Antibody has 2 binding sites = can bind 2 pathogens at same time
  2. Means pathogens & antibodies become clumped together = called agglutination
  3. Phagocytes bind to antibodies and phagocytose many pathogens at once
  4. Process leads to destruction of pathogens carrying this antigen in body


All antibodies have same _____ region

All antibodies have same constant region


What does the constant region allow antibodies to do?

To bind to receptors on B-cells


What does the hinge region allow antibodies to do?

Allows flexibility so molecules can group more than one antigens


Why are antibodies specific to one antigen? (3)

  • Variable region has specific primary structure
  • Tertiary structure of binding site is complementary to bind with these antigens
  • Forms complex between antigen and antibody


What is the primary response?

When antigen enters body for 1st time & activates immune system


Why is the primary response slow?

∵ there aren't many B-cells that can make antibody needed to bind to pathogen


Primary Immune Response

After being exposed to antigens, T- and B-cells produce ____ ___

memory cells


Memory cells remain in body for ____ time


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