BIOL 2020U Lecture Notes - Mitosis, Antigen Presentation, Macrophage

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29 Jan 2013
Antibody (immunoglobin protein)
Secreted by B-lymphocytes and produced in response to a specific (foreign) non-self
B-lymphocyte's receptor site matches the non-self-antigen
Each antibody is produced by one type of B-lymphocyte for only one type of antigen
An antibody is Y-shaped
o The two ends of the Y are called the Fab fragments
o The other end is called the Fc fragment
o Fab fragment is responsible for the antigen-binding properties
o Fc fragment is the effector component and triggers the immune response
B cells divide and form memory cells and antibody-secreting plasma cells:
o Agglutination makes pathogens clump together
o Antitoxins neutralise toxins produced by bacteria
o Lysis digests bacterial membrane, killing the bacterium
o Opsonisation coats pathogen in protein that identifies them as foreign cells
Types of Immune Response
Lymphocytes undergo maturating before birth, producing different types of lymphocytes
Humoral response - B lymphocytes
o Produce and release antibodies into blood plasma
o Produce antibodies from B plasma cells
o Recognize foreign antigen directly
Cellular response - T lymphocytes
o Bind to antigen carrying cells and destroy them and/or activate the humoral
o Recognize foreign antigens displayed on the surface of normal body cells
Primary response produces memory cells which remain in the circulation
Secondary response new invasion by same antigen at a lower state. Immediate
recognition and distraction by memory cells -faster and larger response usually prevents
B-Lymphocytes: The Humoral Response
Response for pathogens not entering our cells (e.g. bacterium)
Each B-lymphocyte recognizes only one specific antigen / need T-helper cell to be
Maturation / B-cells develop to give many different variants / specific immune system
responds to
any type of pathogen entering the body
Primary response:
o Pathogen is ingested by macrophages / macrophage displays the pathogens
surface non-self antigen on its surface (antigen presentation)
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