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Microbiology Chap.15

Host Defenses 2: Specific Immunity and Immunization

TermDefinition
Specific Immunity The Third and final Line of defense
Specific Immunity Acquired only after an immunizing event example: Infection or Vaccination
Immunocompetence The body's ability to react to foreign substances
Immunocompetence Development of B and T LYMPHOCYTES
Two Characterizing features of the third line of defense specificity and memory
What does Specificity and Memory do in the third line of defense? Only recognize certain (specific) pathogens
Antigen anything foreign that activate B-cells and T-cells
Immunogen Any substance that induces a state of sensitivity or resistance after processing by the immune system of the body.
Major Histocompatibility Complex (MHC) series of glycoproteins (MHC molecules) found on the surface of all cells EXCEPT red blood cells
Red Blood Cells and MCH Red blood cells have its own markers
If MCH is ABSENT, what will happen to the cell? The cell will be destroyed by the immune system
MHC mark Self verses Self
MHC present antigens
Development of the Dual Lymphocyte System B-cells and T-cells work together
Development of the Dual Lymphocyte System High level of communication between the two cell types
Development of the Dual Lymphocyte System When antigens are presented, both B-cells and T-cells are activated
Steps of the Development of the Dual Lymphocyte System Step 1: Lymphocyte Development Step 2: Presentation of Antigens Step 3 and 4: T-cell Response
Step 1: Lymphocyte Development All lymphocytes arise from the same basic stem cell type
Where do Lymphocytes come from? come from pluripotential
What is Pluripotential? Stem cells having the developmental plasticity to give rise to more than one type. Example: undifferentiated blood cells in the bone marrow.
Step 1: Lymphocyte Development- Final Maturation for B-cells Occurs in specialized Bone Marrow sites
Step 1: Lymphocyte Development- Final Maturation for T-cells Occurs in the Thymus
Step 1: Lymphocyte Development- After maturation of B-cells and T-cells Both cell types migrate to separate areas in the lymphoid organs "going to the dump to shop"
Specific Events in B-cell Maturation Bone marrow sites harbor stromal cells Stromal cells nuture the lymphocytes stem cells and provide chemocal signals that initiate B-cell development B-cells circulate through the blood, "homing" to specific sites in lymph nodes, spleen, and GALT
Specific Events in B-cell Maturation Adhere to specific binding molecules where they come into contact with antigens
B-Cell Receptor Immunoglobulim receptors (Igs) Y-shaped arrangement Ends of forks (of y shape) contain pockets called the antigen binding sites Can be highly variable in shape to fit a wide range of antigens Variable regions (V)-folk Constant regions (C)-handle
Specific Events in T-Cell Maturation Directed by the thymus gland and its hormones Circulate between the lymphatic and circulatory system, migrating to specific T-cell areas of the lymph nodes and spleen Mature T lymphocytes express T-cell receptor and co-receptors (CD-4 or CD-8)
T-Cell Receptor Constant Region Variable Region Antigen binding site Co-Receptor Never Secreted; always attached
Immunological Diversity 500 gene segments that can be rearranged t produce diverse receptor types
Immunological Diversity *Different B and T cells are made which leads to specificity *By the time B and T cells reach the lymphoid tissue they are equipped to respond to a single, unique antigen *Each line of lymphocytes is termed a clone
Step 2: Presenttation of Antigens Perceived as foreign Antigenic Molecule
Antigenic Molecule: Proteins and polypeptides Enzymes, cell surface structure, hormones, exotoxins
Antigenic Molecule: Lipoproteins Cell membrane
Antigenic Molecule: Nucleoproteins DNA complexes to proteins but not pure DNA
Antigenic Molecule: Polysacchararides Certain bacterial capsules
Antigenic Molecule: Haptens small foreign molecules that are too small to elicit an immune response on their own *if linked yo a larger carrier molecule, them the combination develops IMMUNOGENICITY
Role of antigen processing and presentation *Produce APCs *Engulf the antigen and modify it so it is more immunogenic and recognizable - Epitope *After processing, the antigen is bound to the MHC receptor and moved to the surface of the APC so it is accessible to T lymphocytes
What is APC? APC (Antigen-presenting cells): cells that act upon and formally present antigens to lymphocytes *Macrophages *Dendritic cells (related to macrophages) *B cells
Step 3 & 4: B-Cell Response Activation of B Lymhocytes
Activation of B Lymhocytes *Clonal section and binding of antigen *Antigen processing and presentation *B-cell/ T-cell recognition and copperation (T- Helper) *B-cell activation *Clonal expansion (copies) *Antibody production and secretion *Plasma cells and memory cells
What are Memory Cells? Long term B-cells
What are Plasma Cells? Antibody producer factors that is fighting right now
Classes of Immunoglobulins (Igs) B cell receptors (weight and arrangement) IgM- 1st one made during an infection IgA- important in mucosal defense IgD- acts as a receptor IgG- most prevalent AB IgE- Allergies
Antigen- Antibody Interactions Principal activity of antibody: unite with , immobilize, call attention to, or neutralize the antigen for which it was formed
Antigen- Antibody Interactions : Opsonization plasma cells- antibody marks to kills
Antigen- Antibody Interactions: Neutralization not allowing microorganisms to attach
Antigen- Antibody Interactions: Agglutination accumulate; stick together which prevents it from doing what its suppose to do
Antigen- Antibody Interactions: Complement fixation antibodies cause complement and produce MACs (donuts) which cause them to die
Antigen- Antibody Interactions: Antitoxin Antibodies going totoxin don't allow it to find its target and it dies
Monitoring Ab Production: Primary Response *First exposure *Latent period- lack of antibodies synthesis *Synthesis of antibodies -first IgM, second IgG, then some IgM ad IgA *Titers (In immunochemistry, a measure of antibody level in a patient, determined by agglutination methods.)
Monitoring Ab Production: Secondary Response *Re-expossre to the same immunogens *Antibody synthesis, titer, and length of antibody persistence is rapid and amplified *primary due to memory cells
Step 3 & 4: T- Cell Response Cell-Mediated Immunity (CMI)
Cell-Mediated Immunity (CMI) *require the direct involvement of T lymphocytes throughout the course of the reaction *T cells require some type of MHC recognition before they can be activated *T cells stimulate other T cells, B cells, and phagocytes *Cytokine production
What is Cytokine production? production of chemicals produced by T- cells
T cell Activation and Differentiation *Recognize an antigen only with an MHC carrier *T cell is sensitized when an antigen/ MHC complex is bound to its receptors *The activated T cells then transform in preparation for mitotic divisions and differentiate into one of the subsets
T Helper Cells (T H) *Play a central role in regulating immune reactions to antigens *Involved in activating Macrophages -directly by receptor contact -indirect y by releasing cytokines
T Helper Cells (T H) *Secrete interleukin-2 (type of cytokine) *some secrete interleukin- 4,5, and 6 (help activate B-cells)
T Helper Cells (T H): Secrete interleukin-2 stimulates the primary growth and activation of many types of T cells
T Helper Cells (Th): secrete interleukin- 4,5, and 6 stimulate various activities of B-cells
Regulatory T Cells (Tr) *T-cells regualte *Maintain "Happy Medium" *Carry CD4 markers *Control Inflammation *Prevent Autoimmunity *Prevent immune response against normal flora
Cytotoxic T Cells (Tc) *Cytotoxicity *Target cells that Tc cells can destroy include: Virally infected cells, cancer cells, and cells from other animals and humans *After activation the Tc cell severely injures the target cell- secrerion of perforins and granzymes
What is Cytotoxicity? the capacity to kill a specific target cell
What are Perforins? Proteins released by cytotoxic T cells that produce pores in target cells
What is Granzymes? Enzymes secreted by cytotoxic T cells that damage proteins of target cells.
Natural Killer Cells (NKC) *Related to T- cells *Lack specificity for antigens *Circulate through the spleen, blood, and lungs *Probably the first killer cells to attack cancer cells and virus-infected cells
Vaccines Whole bacterial cell or virus -Killer cells or inactive viruses- dead -Live, attenuated cells or viruses- softened Antigenic molecules derived from bacterial cells or viruses
Whole bacterial cells or virus: Dead dead organisms are safest less effective immunogens wrong POE (portal of entry)
Whole bacterial cells or virus: Live live organisms offer better response mimic actual infection mutate back to virulent form
Created by: Jervetteg