Immunology

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Myeloid stem cell

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Determined by chemical mediators, differentiate into RBC's, megakaryocytes, macrophages, granulocytes, dendritic cells or mast cells

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Lymphoid stem cell

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Lymphoid stem cells further differentiate into dendritic cells, t-cells, b-cells, and NK lymphocyte cells

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Innate Immunity

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Begins immediately in response to tissue damage

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physical barriers
mechanical barriers
chemical barriers

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- Skin, mucous membranes
- Ciliary beating, blinking, sneezing
- pH of skin, stomach acid

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Phagocytosis

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Cells are attracted to a specific site of infections or tissue damage in order to engulf and destroy pathogen

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Cytokines

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Small signaling proteins
- signal increased expression in adhesion molecules
- attract leukocytes to infection site
- increase fluid that leaves circulation
- signal bone marrow to produce more leukocytes

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Chemokines

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molecules that set neutrophils and monocytes in motion via chemotaxis (signal via certain chemicals in their environment). Locally produced throughout body

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Adaptive immunity

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Highly specialized, systemic cell and processes that eliminate pathogenic growth
- Antigen specific, only in vertebras
- quicker and stronger response to repeat infection
- efficient enough that symptoms don't develop
- can be long lasting, but usually not permanent

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Adaptive immunity repsonse

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Synthesis of anti-body to antigen and promote elimination
- T-cell (CD4= T helper cells, CD8= T cytotoxic cells) killing of virus infected cells
- T-cell activation of macrophages to destroy phagocytized pathogens resistant to destruction

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Innate and Adaptive Immunity

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Work together to fight off infection
- Innate = fast, immediate response
- Adaptive = slow, more "potent" response

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Primary lymphoid organs

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White cells develop and mature:
- Bone marrow - B cells and Hematopoiesis
- Thymus - where T cells finish development

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Secondary (peripheral) lymphoid organs

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Function to bring together leukocytes and Ag
- Lymph nodes - collect Ag from tissue
- Spleen - blood born antigens encounter immune system
- MALT - mucosa-associated lymphoid tissue (respiratory tract, appendix, peyers patch (lymph tissue of gut))

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Trafficking of Immune Cells

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WBC = T and B cells, enter lymph node via HEV (high endothelial venuoles); hang out, do not need to be in contact with Ag to leave, can leave whenever and continue trough lymph circulation or bloodstream

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Lymphocytes

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Small round cells with a large nucleus
- Antigen specific leukocytes
- Adaptive are called B and T cells
- Each lymphocyte recognizes one specific antigen with receptor
- Each lymphocyte has ~100k identical copies of its membrane antigen receptor

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Membrane Immunoglobulin or B cell receptor or Antibody

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Antigen receptor on B-Lymphocytes (antibody)
- antibodies can bind both protein and non-protein Ag - the site on the Ag where it is bound is called the epitope

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T Cell Receptor

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The antigen receptor on T Lymphocytes
- TCR needs to be presented Antigen by an Antigen presenting cell for it to function (macrophages, b cells, and dendritic cells)

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Immune Repetoïre

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the ability of lymphocytes to undergo recombination to be able to be specific to millions of different Antigens creates a very large immune repertoire

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Mature Naive T and B cells

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Those that have not yet bound nor encountered foreign anti-bodies
- If a lymphocyte binds an Ag it proliferates into a clone of antigen eliminating effector cells (plasma, T cell, T helper)

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Primary response

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1-2 week response time needed for specific T and B cells to activate
- memory cells for this antigen are also produced at this same time

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Secondary response

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After repeat exposure to the same antigen the response is faster, stronger and longer lasting - due to expansion of memory lymphocytes formed during initial exposure

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Response to antigen

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In most cases the body is bombarded with antigens at any given time, the brisk immune response keeps microbial replication under control
- only after a certain threshold has been reached do symptoms present themselves

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Active adaptive immunity

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- Natural infection with the organism
- Vaccination with a killed or weakened (attenuated) pathogen, or inactivated (toxoid)
- takes 1-3 weeks to become established and may be very long lasting (years to lifetime)

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Passive adaptive immunity

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From an immune person by the transfer of antibodies
- starts protection as soon as the antibodies are transferred
- lasts only weeks as transferred antibodies are removed from circulation by process called turnover
- ex: anti-venom after a snake bite