Topic 11 - Animal Physiology Flashcards
antigen
any substance that is recognized as “not-self” by the body
how do white blood cells distinguish between self and not-self?
- all body cells have the same genetic info and a common set of plasma membrane proteins
- any cells with those membrane proteins are “self” and any without those proteins are “not-self”
B lymphocyte
- plasma cells capable of synthesizing specific antibodies to bind to specific antigens
problem with using only B lymphocytes as immune defense
- B lymphocytes are few in number (just 1% of cells in the bloodstream)
- thus cellular communication methods are necessary to lead to the cloning of the appropriate B lymphocyte cell
polyclonal response
i. e. primary immune response
1. A macrophage (large phagocyte) encounters an antigen found on a pathogen
2. The macrophage engulfs the pathogen via phagocytosis and partially digests it
3. Molecular pieces of the pathogen are displayed on the cell membrane of the macrophage (antigen presentation)
4. Helper T cells (leucocytes) recognize the antigen and activate the relevant B lymphocyte
5. Upon activation, the lymphocyte begins a series of cell divisions (cell cloning)
types of cloned B cells
- plasma cells: immediately secretes antibodies to help fight off the primary infection
- memory cells: long-lived, doesn’t secrete antibodies, but retains information on the antigen to be used on secondary infection
true immunity
- occurs after the steps of the primary response
- as memory cells are long-lived, they can respond to a secondary infection more quickly and effectively
antibodies
- Y-shaped protein molecules
- produced by lymphocytes in response to a specific pathogen
- the main difference between each antibody lies in the 2 amino acids at the end of each Y fork
- they’re used to bind to a specific antigen and are identical to each other
ways antibodies help the immune system
- binds to pathogen and marks it for destruction
- binding pathogens together (agglutination) to help phagocytic cells locate them
how does a vaccine confer immunity without resulting in symptoms?
- vaccines are composed of the chemical components of a pathogen after the disease-causing abilities have been removed
- however, leucocytes still recognize the antigen as not-self
- so the primary immune response still takes place
how can diseases cross from one species of host to another?
- a protein to protein match must occur for a virus to recognize another species’ cell as a host cell
- this normally happens if the two species are in close contact for extended periods (i.e. long enough for viral mutations to occur)
why is the primary immune response also called a “polyclonal response”?
- a virus’ capsid (protein coat) is made up of multiple types of protein
- so it’s typically recognized as more than one antigen
- each of the protein types stimulate an immune response, so more than one B lymphocyte will undergo clonal selection
- once a polyclonal response occurs, it’s difficult to separate the different kinds of antibodies produced
monoclonal antibodies
antibodies of the same type (“pure”)
how are monoclonal antibodies produced?
- An antigen is injected into an animal
- The animal is given time to undergo a primary immune response
- After some time the animal’s spleen is harvested to obtain blood cells
- B leucocytes are isolated and grown together with myeloma cells under proper conditions, resulting in their fusion to form hybridoma cells (retains their function but with extended lifespan)
- The entire mix is transferred to an environment only the hybridoma cells can survive; each hybridoma cell is then isolated to be cultured in separate containers
- Each container is given the ELISA (enzyme-linked immunosorbent array) test to test for a specific protein – this test identifies which containers hold a pure colony of B cells that produce the specific antibody desired
example of monoclonal antibody usage
- pregnancy testing
- the hormone human chorionic gonadotropin (HCG) is only produced by the embryo
- so it can only be found in the bloodstream of pregnant women (and even then only in small amounts)
- hybridoma cells can be formed that produce antibodies specific to HCG
- those anti-HCG antibodies can be chemically bonded to an enzyme that catalyses a color change when the antibody encounters HCG
