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2012.03.26 - Bio 1202 Lecture Review Notes.docx

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Western University
Biology 1202B
Gardiner/ Murphy

Biology Lecture Review Notes Lecture 11 Adaptive Immune System  Hematopoietic stem cells form all the blood cells o They are the cells of the immune system (for organs, tissues and cells that work to prevent and heal disease) o All of the differentiated cells look much different from one another  Adaptive immune system – specifically recognizes foreign molecules and removes them from the body o Foreign molecules can be free, found on the surface of a virus, cancer cells, pollen, or transplanted organs o Since the reaction is specific, it may take several days to become effective o Makes a memory for the foreign material, so ready to attack if it returns in the future o Plays a big role in transplant rejection  Adaptive immunity o Antigen – any foreign substance (endogenous or exogenous) that can create an adaptive immune response  Endogenous – normally found within the body  Exogenous – normally found outside the body  Examples: bacteria, viruses and parasites o Antigens are recognized by two types of lymphocytes:  B lymphocytes (B cells) – released into the blood and carried to capillary beds for the tissues and organs of the lymphatic system  Differentiate from stem cells in the bone marrow  T lymphocytes (T cells) – released into the blood and carried to the thymus (an organ of the lymphatic system), where they differentiate  Produced by the division of stem cells in the bone marrow o Leukocytes (WBC) in mice were killed by irradiation (so they were unable to generate an immune response) and injecting lymphocytes from normal mice into these irradiated mice restored the adaptive immune response, but other injected cells did not  Demonstrates that these cells recognize antigens  There are two types of adaptive immunity responses: o Antibody mediated immunity (AMI) or humoral immunity o Cell-mediated immunity (CMI) o Both have similar mechanisms, which include:  Lymphocyte recognizes and binds to antigen  Lymphocyte divides to produce a large # of clones  Activated lymphocyte clears antigen from body  Activated lymphocytes differentiate into memory cells that circulate in the blood and lymph ready to initiate a rapid immune response upon seeing same antigen, thus development of immunological memory  Antibody mediated immunity (AMI) – body produces proteins called antibodies, which destroy or neutralize an antigen o Antibodies are symmetrical and composed of light (shorter) and heavy (longer) chains of amino acids  The amino acid chains are held together by disulphide bonds  Antibody in a B-cell is made up of 4 chains  Antibody in a T-cell is made up of 2 chains o Antigens bind to the end of the antibody because they recognize them as complementary sequences (the antibodies are very specific for specific antigens)  Each B and T cell has antigen specific identical receptors on its plasma membrane called B cell receptors (BCR) and T cell receptors (TCR) respectively o Each B or T c
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