14.4 Flashcards
(21 cards)
What is humoral immunity? & What type of cell primarily mediates it?
(1) Immunity involving antibodies,
(2) which are soluble in blood and tissue fluid
(3) B lymphocytes (B cells)
What key characteristic do B lymphocytes have for them to achieve humoral immunity? (2)
(1) Each B cell produces a specific antibody
(2) that responds to one specific antigen
Define the term “antigen”
(1) a protein on the surface of a
(2) pathogen, foreign cell, toxin, or damaged or abnormal cell
Describe the process of clonal selection in B cells (6)
(1) A B-cell with a specific antibody that exactly fits the antigen that entered the body
(2) attaches to the complementary antigen.
(3) The antigen is taken into the B cell by endocytosis, are processed then presented on its surface membrane.
(4) Specific T helper cells bind to these processed antigens & stimulate the B cell.
(5) The stimulated B cell divides by mitosis to form a clone of identical B cells.
(6) All cloned B cells produce the antibody specific to the foreign antigen
NOTE: B-cells with the appropriate antibody binds to the antigens of a pathogen. Antibodies are not produced in response to the pathogen. They are present from birth. Being present, they simply multiply in response to the pathogen.
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After clonal expansion, the B cells become either memory cells or plasma cells.
What is the main function of plasma cells? (3)
What is their lifespan? (1)
(1) they secrete antibodies, usually into blood plasma,
(2) which destroy the antigens.
(3) it’s responsible for the primary immune response of the body.
(1) they’re short-lived - they only live a few days
After clonal expansion, the B cells become either memory cells or plasma cells.
What is the role of memory cells in immunity? (4)
HINT: the graph of the difference between the secondary & primary immune response (figure 1 in page 183)
(1) they’re responsible for the secondary immune response
(2) When they encounter the same antigen at a later date, they divide rapidly & develop into plasma cells & more memory cells (to produce antibodies faster).
(3) an increased quantity of antibodies is secreted at a faster rate in the secondary immune response than in the primary immune response.
(4) so the memory cells provide long-term immunity against this specific pathogen.
Describe the process of humoral immunity. (7)
(1) the surface antigens of an invading pathogen are taken up by a B cell via endocytosis
(2) the B cell processes the antigens & presents them on its cell surface membrane
(3) Helper T cells attach to the processed antigens on the B cell, thereby activating the B cell
(4) The activated B cells divide by mitosis to give a clone of plasma cells
(5) The cloned plasma cells produce & secrete the specific antibody that exactly fits the antigen on the pathogen
(6) The antibody attaches to antigens on the pathogen & destroys it
(7) some B cells develop into memory cells. These can respond to future infections by the same pathogen by dividing rapidly & developing into plasma cells that produce antibodies. This is the secondary immune response.
NOTE: to visualize the process of humoral immunity, check figure 2 on page 184
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What are antibodies made of? (1)
Protein(s)
Describe the secondary immune response and how it differs from the primary response. (2)
(1) The rapid & enhanced response to a second exposure to the same antigen
(2) there’s a faster rate of antibody production & a higher concentration of antibodies in the secondary response compared to the primary response
How can antigenic variation affect the body’s response to infection? (2)
(1) Changes in the antigens on the surface of pathogens can lead to memory cells not recognizing the altered antigens,
(2) potentially reducing the effectiveness of the secondary response
Describe the structure of antibodies. (7)
(1) they’re made up of 4 polypeptide chains.
(2) of these 4 chains, 2 are light & short and 2 are heavy & long
(3) these chains are connected by disulfide bridges
(4) has a specific binding site that fits very precisely onto a specific antigen to form ANTIGEN-ANTIBODY COMPLEXES
(5) The binding site is part of the variable region
(6) The rest of the antibody is the constant region
(7) which binds to receptors on cells such as B cells
In antibodies, each ___(1)___ site consists of a sequence of __(2)__ __(3)__ that form a specific ___(4)___ structure that binds directly to a specific ___(5)___.
(1) binding
(2) amino
(3) acids
(4) tertiary
(5) antigen
Antibodies do not directly destroy the antigens on foreign cells & microorganisms, but they prepare the antigen.
How do antibodies lead to the destruction of pathogens and foreign cells? (2)
(1) They cause agglutination (clumping) of antigen-presenting cells, making it easier for phagocytes to locate them
(2) They act as markers, stimulating phagocytes to engulf cells
What is agglutination? (1)
Why is agglutination possible? (1)
(1) it is the clumping of cells or particles
(1) Because each antibody has 2 antigen-binding sites
Explain why the secondary immune response is much more rapid than the primary one. (5)
(1) In the primary response, the antigens of the pathogen have to be ingested, processed and presented by B cells.
(2) Helper T cells need to link with the B cells that then clone, with some of the cells developing into the plasma cells.
(3) These processes occur consecutively and therefore take time.
(4) In the secondary response, memory cells are already present, and the only processes are cloning and development into the plasma cells.
(5) Fewer processes means a quicker response.
Contrast the cell-mediated and humoral responses to a pathogen. (4)
(1) CM : involves T cells
H : involves mostly B cells
(2) CM : No antibodies
H : antibodies produced
(3) CM : first stage of immune response
H : second stage of immune response (after CM)
(4) CM : effective through cells
H : effective through body fluids
Plasma cells can produce around 2000 protein antibodies each second. Suggest 3 cell organelles that you might expect to find in large quantities in a plasma cell, and explain why. (3)
(1) Rough endoplasmic reticulum - to make & transport the proteins of the antibodies
(2) Golgi apparatus - to sort, process, & compile the proteins
(3) Mitochondria - to release the energy needed for such massive antibody production
TASK: Draw & label the structure of antibodies. (7)
Check out that slide Ms Antonia printed for you that showed the detailed structure of antibodies OR check figure 4 on page 185.
All of these below must be correctly labelled:
(1) Light chains
(2) Heavy chains
(3) Antigen-binding sites
(4) Variable region
(5) Constant region
(6) Receptor binding site
(7) Disulfide bridges/bonds
ADDITIONAL TASK: Blurt by drawing the process of Humoral Immunity and label your diagram. (7)
Check answer from Figure 2 from Page 184
