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41 Cards in this Set
- Front
- Back
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Two types of lymphocytes involved in adaptive immunity |
Originate from stem cells in bone marrow T cells: mature in thymus B cells: mature in bone marrow Also Natural killer cells (third type) are active |
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3 main functions of the lymphatic system for homeostasis |
1. Lymphatic capillaries take up excess tissue fluid and return it to bloodstream 2. Small lymphatic absorb fats from digestive track and transport to bloodstream (lacteals) 3. Lymph cells defend the body against disease |
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Lymph |
Tissue fluid Derived from plasma nutrients, electrolytes, and oxygen Contains cellular products secreted by cells, hormones, enzymes and waste Also has white blood cells |
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Lymphatic vessels |
Lacteals: lymphatic capillaries closed end vessels, simple squamous epithelium Travel to larger lymphatic vessels like cardiovascular system Like stations where lymph is screened and filtered |
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Lymph movement |
Skeletal muscle contraction helps to move lymph Flows in one direction: lacteals to large lymphatic vessels to 2 ducts (thoracic duct and right lymphatic duct) |
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Thoracic duct |
Lymph below thorax, left arm, left side of had and neck into left subclavian vein |
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Right lymphatic duct |
Lymph from right arm, thorax, right side of head and neck into right subclavian vein |
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Lymphoid organs |
Red bone marrow Thymus gland (located behind sternum above heart) |
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Red bone marrow contains |
Site of blood cells production from stem cells B and T cells produced in bone marrow B cells mature in bone marrow |
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Thymus gland |
T cells migrate from bone marrow and mature here T cells that react to the body’s own cells undergo apoptosis (distinguish self from non self) Only 5% of T cells leave thymus |
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Secondary lymphoid organs where some lymphocytes become activated |
Spleen: mostly red pulp that filters blood with white pulp as lymphatic tissue Lymph nodes: cleanse lymph, packed with B and T cells, engulf pathogens |
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Afferent lymphatics |
Bring to |
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Efferent |
To bring out |
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Antigens |
Any foreign substances that elicit a response from B or T cell Large molecules, proteins or polysaccharides on surface of viruses or bacteria T it B cells bind to antigens via antigen receptors specific to the molecules of pathogen |
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Epitope |
Small accessible part of an antigen, bind to receptors Individual B or T cells are specialized to recognize one one particular epitope on an antigen Antigen receptors of B and T cells have similar components but encounter antigens in deodorant ways |
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B cell antigen receptors (IgD) |
Y-shaped with 2 identical heavy chains and 2 identical light chains linked by disulfide bridges Constant regions of the chains vary little Variable regions differ greatly, these provide antigen binding sites |
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Antigen receptor |
2 identical antigen-binding sites on each B-cell antigen receptor One B cell produced many B cells that are identical and unique to antigen epitope |
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B cell activation (antibodies) |
B cell binds to epitope and gives rise to plasma B cells (soluble form of a protein called an antibody or immunoglobulin (lg) Antibodies have same Y shape as B cell antigen receptors bit are secreted, not membrane bound |
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Antibodies structure (5) |
Immunoglobulin (Ig): all have different heavy c chain regions IgD: only one that has transmembrane tail IgA: dimer can bind 2, found digestive system IgE: longest heavy chain, clears out parasites IgG: most abundant in blood and plasma. 2nd in line to be produced IgM: can join 5 receptors, 1st to develop |
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Table |
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T cell receptor |
Consists of two polypeptide chains (alpha and beta) Tip of chain is variable region for one binding site Rest of molecule is constant region |
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T and B cells receptors function differently |
Antigen receptors of B cells bind to epitope of of intact antigens and toxins in body fluids Receptors of T cells bind only to fragments of antigens that are presented on surface of infected cell (host cell engulfs pathogen and then exposes receptor) |
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T cell recognition (antigen presentation) |
Pathogen is consumed by host cell, enzymes cleave antigen into smaller peptides Each peptide (antigen fragment) binds to an MHC molecule inside the cell T cell now recognizes fragment on host cell |
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Major histocompatibility complex (MHC) |
Proteins that Bind fragments to surface of cell Different classes (I and II) attract different T cells |
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Major histocompatibility complex (MHC) |
Proteins that Bind fragments to surface of cell Different classes (I and II) attract different T cells |
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4 major characteristics of the adaptive immune system |
1. Immense diversity of lymphocytes and receptors (detect pathogens never before encountered) 2. Self-tolerance: lack of reactivity against animals own cells 3. B and T cells proliferate after activation 4. Immunological memory: stronger and rapid response to a previously encountered antigen |
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Adaptive immunity |
A mature lymphocyte encounters and binds to a specific antigen Follow by proliferation of the lymphocyte and the formation of immunological memory |
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B and T cell diversity |
Each person makes: >1 million different B cell antigen receptors >10 million different Tcell antigen receptors 20,000 protein coding genes in human genome Numerous diversity of receptors |
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Receptor diversity and self-tolerance arise as a lymphocyte matures |
Many different chains can be produced from the same gene by rearrangement of the DNA sequence of the V, J, and C regions An immunoglobulin gene encodes the light chain of the Bcell receptor Rearrange DNA is transcribed and translated to form antigen receptor |
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A receptor light chain is encoded by 3 segments |
The V and J segments encode variable region C segment encodes constant region Light chain gene contains a single C segment, 40 different V segments, and 5 J Segments |
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Assembling of light chain |
A functional Ig gene requires rearranging DNA Functional gene is built from one copy of each type of segment (pieces can be combined in 200 different ways) |
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Recombinase |
An enzyme complex that act randomly by linking on light chain V gene segment to one J gene segment in each B cell |
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Arrangement of heavy chains |
Undergo similar to light, but heavy chains so even greater: V gene: 123-129, Diversity gene: 27, joining gene: 9, constant gene: 11 In any given cell, there is only one light and one heavy chain gene that are rearranged Rearrangements are permanent and passed on to daughter cells when lymphocytes divide
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For total pop of B cells, number of combos can be up to 3.5x10^6 |
Mutations during VJ recombination in light chain and VDJ combination in heavy chain add more variation |
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Negative selection |
B and T cells with receptors to the body’s molecules are destroyed by apoptosis As lymphocytes mature in bone marrow or thymus, they are tested for self-reactivity |
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Clonal selection |
Multiple cell divisions once anB or T cell is activated Some cells from clone are short lived (effector cells) |
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Effector cells |
Short-lived Cloned cells that act immediately against antigen Effector B cells are plasma cells which secrete antibodies Effector T cells are helper cells and cytotoxic T cells |
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Long-lived memory cells |
Some cells from the clones Can give rise to effector cells of the same antigen is encountered again |
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Immunological Memory |
Responsible for long-term protection from prior infection or vaccination Primary immune response occurs: 1st exposure to antigen (7 day) Clone of lymphocytes is formed Secondary immune response: memory cells facilitate faster response from reservoir of T and B cells |
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Maturity chart |
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