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UMass Amherst MICROBIO 310 - Immunity

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Microbio 310 1st Edition Lecture 24 Outline of Last Lecture I. 27.1 Overview of Human-Microbial InteractionsII. 27.7 Entry of the Pathogen into the Host-AdherenceIII. 27.8 Colonization and InfectionIV. 27.9 InvasionV. 27.10 ExotoxinsVI. 27.11 EndotoxinsOutline of Current Lecture I. 28.1 Cells and Organs of the Immune SystemII. 28.2 Innate ImmunityIII. 28.3 Adaptive ImmunityIV. 28.4 AntibodiesCurrent Lecture28.1 Cells and Organs of the Immune System• 0.1% of blood cells are leukocytes– Include monocytes and lymphocytes (white blood cells)– Cytokines influence the development of stem cells• Whole blood is composed of plasma and cells – Plasma contains proteins and other solutesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• Serum is the portion of blood that is not cells or clotting proteins• The lymphatic system is a separate circulatory system that drains lymph fluid from extravascular tissues • Blood is pumped through arteries and capillaries and returns from the body through veins• In capillary beds, leukocytes and solutes pass from blood into the lymphatic system• Lymph nodes contain high concentrations of lymphocytes and phagocytes• Trust your gut-it’s the interphase between you and the outside world• Fearless poop pills- virus that makes mice not fear cat urine because the virus wants to be in the cat’s gut to continue its life cycle• Mucosa-associated lymphoid tissue (MALT)– Contains lymphocytes and phagocytes– Interacts with antigens and microorganisms • From gut• From respiratory tract• From other mucous membranes• White pulp of spleen also contains lymphocytes and phagocytes• Leukocytes are nucleated white blood cells (WBCs)– Lymphocytes are specialized leukocytes involved exclusively in adaptive immune response• Two types of lymphocytes:– B cells originate and mature in bone marrow– T cells originate in bone marrow, but mature in thymus (Thymus goes away as you age) o ~95% of pre-T-cells that enter the thymus are killed because they don’t work correctly. T-cells die if they don’t bind to antigens or bind to self-cells, causing an autoimmune disease.• Bone marrow and thymus are primary lymphoid organs• Myeloid cells are derived from a myeloid precursor cell– Can be divided into two categories:• Antigen-presenting cells (APCs) engulf, process, and present antibodies to lymphocytes– monocytes, macrophages, and dendritic cells• Granulocytes contain toxins or enzymes that are released to kill target cells– neutrophils, basophils, eosinophils28.2 Innate Immunity• Innate immunity (nonspecific immunity)– The non-inducible ability to recognize and destroy an individual pathogen or its products– Does not require previous exposure to a pathogen or its products– Involves recognition of common pathogen-associated molecular patterns (PAMPs) on pathogens– Mediated by phagocytes (phagocytes recognize and bind PAMPS)28.3 Adaptive Immunity• Adaptive immunity– The acquired ability to recognize and destroy a particular pathogen or its products– Dependent on previous exposure to the pathogen or its products– Directed toward an individual molecular component of the pathogen (antigen)– Following first antigen exposure, a primary immune response occurs– Stimulation of specialized antigen-reactive immune leukocytes (lymphocytes: T and B cells)– Each lymphocyte produces a unique protein that interacts with a single antigen• T cells: T cell receptors (TCRs)• B cells: antibodies or immunoglobulins (Igs)– Begins with interactions of immune T cells with antigens on infected cells– T cells can recognize antigen only when presented on self-proteins called major histocompatibility complex (MHC) proteins• T lymphocyte subsets– T-cytotoxic (TC) cells• Recognize antigen presented by MHC I protein on an infected cell• Kill antigen-bearing target cells directly using Perforin (makes holes in membrane) and Granzyme– T-helper (TH) cells• Interact with peptide–MHC II complexes on the surface of antigen-presenting cells• Act through cytokines to promote immune reactions– TH1 cells• Initiate inflammation/swelling and immunity by activating macrophages • Positive TB test = swelling– TH2 cells• Stimulate antigen-reactive B cells to produce antibodies28.4 Antibodies• Antibodies (immunoglobulins) are soluble proteins made by B cells in response to exposure to non-self antigens• B cells display antibodies on their cell surfaces that directly interact with antigens to cause B cells to ingest pathogen via phagocytosis• B cells then produce many pathogen-derived peptide antigens that are presented to antigen- specific TH2 cells• TH2 cells do NOT interact directly with pathogens, but stimulate other cells (e.g., antigen-reactive B cells, which uptake and degrade pathogens)• Activated B cells differentiate into plasma cells that produce soluble antibodies (primary antibody response)• Subsequent exposure to the same antigen induces memory (secondary antibody response)• Several different classes of antibodies exist and are distinguished from one another by their amino acid sequence, half-life, distribution in different locations, and structure• Each antibody class has a specific function:– IgM and IgG are found in blood– IgA is found in secretions from mucous membranes– IgE is involved in parasite immunity and allergies – IgD is found on the surface of B cells• Antibodies provide targets for interaction with proteins of the complement system, resulting in destruction of antigens through lysis or opsonization• Antibodies can bind to pathogens• Antibodies can bind to toxins and inactivate the


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UMass Amherst MICROBIO 310 - Immunity

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