micro quiz

• Immunology is the scientific study of the immune system and immune responses
• The primary functions of the immune system are to:

  – Differentiate between “self” and “nonself”

  – Destroy that which is “nonself”
• Cells involved in immune responses originate in bone marrow; three lines of lymphocytes are derived from lymphoid stem cells of bone marrow: B lymphocytes (B cells), T lymphocytes (T cells), and natural killer cells (NK cells).
• There are two categories of T cells:

  – Helper T cells and cytotoxic T cells
• There are two major arms of the immune system:

  – Humoral immunity— where special glycoproteins called antibodies are produced by B cells to destroy specific microbes

  – Cell-mediated immunity— involves a variety of cell types, with antibodies playing only a minor role, if any
• Fill in the blanks

  A) antibodies

  B) humoral immunity

  C) macrophages

  D) T helper cells

  E) cytotoxic T cells

  F) delayed hypersensitivity T cells

  G) natural killer cells

  H) killer cells

  I) granulocytes

  
• Acquired immunity —immunity that results from the active production or receipt of antibodies during one’s lifetime
• Active acquired immunity:

  • Antibodies are produced within the person

  • Usually provides long-lasting protection
• Passive acquired immunity:

  • Antibodies are received that were produced by another person(s) or by an animal

  • Usually provides only temporary protection
• Two types of active acquired immunity:

  – Natural active acquired immunity —occurs naturally

  – Artificial active acquired immunity —artificially induced
• Artificial active acquired immunity results when a person receives a vaccine
• A vaccine is defined as material that can artificially induce immunity to an infectious disease, usually following injection or ingestion of the vaccine.
• Most vaccines are made from living or dead pathogens or the toxins that they produce.
• Vaccines stimulate the recipient’s immune system to produce protective antibodies (i.e., antibodies that will protect the person from disease).
• Types of available vaccines:

  – Attenuated vaccines

  – Inactivated vaccines

  – Subunit vaccines

  – Conjugate vaccines

  – Toxoid vaccines
• Passive Acquired Immunity

  • Antibodies produced in one person are transferred to another person to protect the latter from infection— provides temporary protection.
• Natural passive acquired immunity

  • Small antibodies, IgG, present in mother’s blood cross the placenta to reach the fetus

  Artificial passive acquired immunity

  • Antibodies from an immune person are transferred to a susceptible person (e.g., hepatitis B immunoglobulin).
• Antigens

  – Foreign organic substances that are large enough to stimulate the production of antibodies

  – Substances capable of stimulating antibodies are said to be antigenic (or immunogenic).

  – A bacterial cell has many molecules (antigenic determinants) on its surface that are capable of stimulating the production of antibodies.
• Antibodies

  – Proteins produced by lymphocytes in response to the presence of an antigen

  – Belong to a class of proteins called immunoglobulins— globular glycoproteins in the blood that participate in immune reactions
• Fill in the blanks

  A) Antigen-binding site

  B) Light chain

  C) Disulfide bond

  D) Carbohydrate

  E) Fc fragment

  F) Heavy chains

  G) Variable

  H) Constant

  
• Antibodies

  – The amount and type of antibodies produced by a given antigenic stimulation depend on the nature of the antigen, the site of antigenic stimulus, the amount of antigen, and the number of times the person is exposed to the antigen.

  – The majority of antigens are referred to as T-dependent antigens because T cells are required in their processing; the processing of T-independent antigens requires only B cells.
• Fill in the blanks

  A) B cell with specific antigen donor

  B) B cell binds to antigen

  C) Activated B cell multiplies

  D) B memory cells

  E) Plasma cells

  F) Antibodies

  
• • Antibodies

  – The processing of either T-dependent or T-independent antigens results in B cells developing into plasma cells, which are capable of secreting antibodies.
• The initial immune response to an antigen is called the primary response; it takes 10 to 14 days for antibodies to be produce
• The increased production of antibodies following the second exposure to a particular antigen is called the secondary response.
• Immune responses to antigens in the blood are usually initiated in the spleen; responses to microbes and other antigens in tissues are generated in lymph nodes located near the infected area.
• Antibodies are a class of glycoproteins called immunoglobulins; five types— IgA, IgD, IgE, IgG, and IgM.
• All antibodies are immunoglobulins, but not all immunoglobulins are antibodies!
• Fill in the blanks

  A) Nonsecretory IgA

  B) Heavy chain

  C) Disulfide bonds

  D) Light chains

  E) IgD

  F) IgE

  G) IgG

  H) J chain

  I) Secretory piece

  J) Secretory IgA

  K) IgM

  
• Long-lived, antibody-producing cells called hybridomas are produced by combining a single plasma cell and a rapidly dividing tumor cell.
• Hybridomas are capable of producing large amounts of specific antibodies called monoclonal antibodies.
• Monoclonal antibodies are used in immunodiagnostic procedures (i.e., immunologic procedures used in laboratories to diagnose diseases).
• Monoclonal antibodies are being evaluated for possible use in fighting diseases, killing tumor cells, boosting the immune system, and preventing organ rejection.
• When an antibody combines with an antigen, an antigen– antibody complex (or immune complex) is formed.
• Antigen–antibody complexes are capable of activating the complement cascade, which results in some of the following effects:

  – Activation of leukocytes

  – Lysis of bacterial cells

  – Increased phagocytosis as a result of opsonization
• Antibodies are unable to enter cells.
• Cell-mediated immunity (CMI)

  – A complex system of interactions among many types of cells and cellular secretions (cytokines)

  – An arm of the immune system capable of controlling chronic infections by intracellular pathogens (e.g., certain bacteria, protozoa, fungi, and viruses)
• – Examples of cells that participate in CMI: macrophages, TH cells, TC cells, NK cells, and granulocytes
• Natural Killer (NK) Cells

  – NK cells are a subpopulation of lymphocytes called large granular lymphocytes.

  – They resemble lymphocytes, but lack typical T or B cell surface markers.

  – Do not proliferate in response to antigen and appear not to be involved in antigen-specific recognition.

  – NK cells kill target cells, including foreign cells, host cells infected with viruses or bacteria, and tumor cells.
• Hypersensitivity refers to an overly sensitive immune system