ch 15 pt 1 ppt

Microbiology Chapter 15The Immune system: Specific defenses Specific immunityThe immune system is a network of cells and organs that extends throughout thebody and functions as the third line of defense against invaders. It is a specificresponse and it generates specific chemicals to counteract invaders.1. Foreign substances are antigens2. Proteins made by the body in response are called antibodies

Microbiology Chapter 15Two types of immunity:1. Active: the individual own immune system produces the immunityA. Naturally acquired: by diseaseB. Artificially acquired: vaccination

2. Passive: either have antibodies passed from mother to child or having immune globulin administered medically

Microbiology Chapter 15Antigens: The body can recognize materials as non-self or foreign material. These materials are called antigens.Generally protein or large polysaccharides, nucleic acids or lipids are antigenic only if combined with protein or polysaccharides

2. Any cell, part of a cell, or chemical that induces an immune response bythe B-cells or T-cells (lymphocytes), is called antigenic.

3. Usually large molecules 10,000 mw, in many cases the antigen is some particular part of a cell like a cell wall polysaccharide, capsule material,flagella, or fimbriae

Microbiology Chapter 15Antigens: The body can recognize materials as non-self or foreign material. 4. Viral protein, pollen, other protein (egg or milk protein) can cause an immune response and are antigenic.

5. Antibodies tend to react with specific parts of an antigen called and antigenic determinant or epitope. Size and shape; lock-key just like in enzyme substrate interactions.6. Small molecules that are too small to cause an immune response are called haptens. Penicillin is an example. By itself, too small to be antigenic, butit combines with serum proteins and then can become antigenic (penicillin allergy )

Fig. 15.8

Microbiology Chapter 15Antibodies are produced by Lymphocytes1. T or B cell lymphocytes recognize foreign material as antigens.2. They have receptor sites on their cell surface that bind antigens in order to eliminate them as foreigners.3. The antibody molecules are large proteins that are specific in size and shape to interact chemically with their particular antigen.Antibody structure: several kinds of antibodies (chart on pg ____)

Microbiology Chapter 15

G M A D E1. IgG Monomer, simple antibody, Y shaped, composed of two heavychains and two light chains,

a. The y ends have a variable region, amino acid sequence can vary, thus allowing specific interaction with their specific antigen theyhave two antigen binding sites

b. Constant region, on the molecules stem, this c region is calledconstant, it can be different (actually have 5 different c region types giving 5 different types of antibodies)

c. IgG- most prevalent ab, found in blood and it is called monomer forits simple shape

d. When acting on antigen, enhances phagocytosis, neutralizes toxins

e. Since it is small, it passes the placenta and provides passiveimmunity to infants

Microbiology Chapter 15G M A D E2. IgM Pentamer, composed of 5 monomers (5 Y monomer units)a. Large and stays in blood stream or attaches to blood cells

b. The first kind of ab to appear after an antigenic challengec. Involved in clumping (agglutination) reactions, works with complement and clumps antigens and cells, so the can be easily phagocytized

d. Kind of reaction seen with ABO blood grouping

Microbiology Chapter 15G M A D E3. IgA Secretory antibody, secreted along epithelium liningsa. Found in respiratory tract, GI tract, mothers milkb. Localized protection

4. IgD function not well known, found on b cell surfaces, may function in initiation of immune response (B cell activation)

5. IgE bound antibodies, found on surfaces of mast cells, stimulates inflammatory response, may be a trigger for allergic response

Microbiology Chapter 15The immune response: B cell immunity (Humoral immunity) **** Know for test ****

The B cells are lymphocytes that develop from stem cells located in the red bone marrow.

1. In embryonic development, stem cells differentiate into b cells2. Some move to thymus gland and become T cells3. Both B and T cells later migrate to other lymph tissue (lymph nodes, spleen)4. When B cells are exposed to antigens, they are activated, they start to divide and become a clone of many effector cells called plasma cells


The B cells are lymphocytes that develop from stem cells located in the red bone marrow.

5. The plasma cells produce the antibodies that counteract the specific antigen that activated the original B cells

6. Theory of antibody production Clonal selectiona. During development the B cells undergo tremendous geneticrecombination that results in literally millions of different receptor sites on their surfaces. These receptor sites are able to bind with the specific shape of specific antigens.

b. Because of the tremendous number of potential genetic combinations on the gene regions that code for these antigen recognition sites millions of possibilities result millions of genetically different B cells

Microbiology Chapter 15The B cells are lymphocytes that develop from stem cells located in the red bone marrow

c. Recognition an antigen enters the host, only one or a few b cells have a site on its surface that fits that antigen (better the fit, the betterthe immune response) antigenic selection antigen selects its B celld. The specific matching b cell is now activated and undergoes cell division into many cells (a clone) *****Clonal selection*****e. See pg ___ -know this for the test be able to diagram andexplain

Microbiology Chapter 15i. Recognition

ii. Activation

iii. Proliferation

iv. Differentiation (plasma cells, memory cells)

v. Production of antibodies (secreted into plasma)

vi. Memory cells long lived cells, survive and can respond very quickly if encounter antigen again (immunological memory)


The first reaction recognition - activation proliferation - etc. Takestime - This is the primary response 1 to 2 weeks (pg____)

Secondary response is very quick memory B cells can respondquickly to produce more b cells and antibodies, just a few days

How does the body know the difference between self and non-selfmaterial??

Still a mystery self tolerance, the forbidden clone?? Maybethe B and T cells that are exposed to self antigens are destroyed in fetal development when they pass through the thymus gland (clonal deletion)

Microbiology Chapter 15T cell responseT cells T lymphocytes, cell mediated immunity just touch on it a little

1. T cell activation is different than that of B cells2. The antigen that is presented to the T cell is first processed by antigen presenting cells usually a macrophage

a. Macrophage encounters antigen ingests it, digests it and then seperates it into antgenic determinantsb. Antigenic determinants migrate to the phagocyte cell surfacec. Antigens are held on surface of the phagocyte

Microbiology Chapter 153. The correct T cell encounters the antigen on the phagocyte and is activated4. T cells then can divide and differentiate into different types of T cells(be able to list and give a function)a. T-helper cells (Th) most prevalent, secrete lymphokines(interleukins chemical messengers between cells of the immune system) see pg ____

b. Cytotoxic T cells (Tc) destroy target cell when in contact(virus infected cell killed before virus can replicate)

c. T suppressor cells (Ts) may regulate the immune response, turns it off when not needed

d. Td delayed hypersensitive cells cause inflammationreaction associated with hypersensitivity, and some of the problems with tissue rejection

Microbiology Chapter 15Diagnostic ImmunlogyMany diagnostic tests in microbiology are based on immunology

1. Ag Ab reactions can b used to determine presence of infection or an exposure to an antigen2. Hiv test, Hep C are used to determine exposure to these viruses

3. Clinical immunology (serology) is the branch of immunology involved with identifying cause of diseases based on the presence of antigens or antibodies in serum of patients

4. a good diagnostic immunological test should meet two criteria

a. Specificity test will indicate the presence of only one particular antibody or antigen , wont react with even closely related Ag or Ab

b. Sensitivity can detect even tiny amounts of antibodies or antigens in serum


c. Titer the serum, with antibodies, is diluted and the dilutions are tested for antigens. The highest dilution that still tests positive (a visible reaction) with the antigen is the titer

5. Agglutination test: easy to see and read, type of test for blood types.a. Whole cells are tested for presence of antigens on their surfacesb. Antiserum is added, if positive (specific ag ab reaction), clumping or aggregation of cells occurs ( blood typing pg ___)c. A,B,O blood groups, rh factor testing ( Photo atlas, in lab, page 108-109)i. A a ag, antib abii. B- b ag, anti a abiii. AB both a and b ag and no anti a or b abiv. O neither a or a antigen, both anti a and anti b ab


6. Elisa test (EIA test) enzyme linked immunosorbent assay (pg 532)

a. Widely used in clinical labs, adaptable for direct assay to detect presence of antigen or indirect assay by testing for the presence of antibody

b. These tests can be easily automated and results determined by a computer

Direct ELISA (photo atlas pg 110 111) handout1. Ab for a specific Ag attached to the plastic microtiter well2. Test Ag is added, if it binds, then add enzme-linked abspecific for the test ag3. Then a substrate that is specific for that enzyme is added.This will produce a specific color change4. The enzyme and substrate are selected so that a specificcolor is produced that can be detected in the computer using optical density reader

Microbiology Chapter 15ii. Indirect like the HIV test. Known antigen is attached to the well. Test antiserum is added. If it is complementary to theantigen, it binds. p.532

Other tests: Complement fixation test pg 529 Fluorescent AB pg 530,Precipitin, Western blot test (confirmatory for HIV after ELISA)

ch 15 pt 1 ppt

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