Immunology Part 1

IMMUNOLOGY

PHYSIOLOGY
1.    IMMUNOGENS	Chemical compounds that cause specific immune response
2.    ANTIGENS	Chemical compounds that BIND TO THE PRODUCTS of an immune response
3.    IMMUNOGEN-ANTIGEN	Compound associated with or secreted by parasitic bacteria, protozoa, fungi and viruses an of MW >5,000 daltons n  For the cmpd to be immunogenic,it must contain protein or peptide n  Insulin
4.    HAPTENS	Low MW cmpds that act as immunogens after COVALENTLY binding to a larger molecule or cell surface. After they stimulate the immune system in this complex, these compounds can act as ANTIGENS in the unbound or bound state n  May be present in environment (EX: Pentadecacatechol of poison ivy) n  Drugs such as PENICILLIN
5.    TOLEROGENS	Chemical compounds that elicit specific nonresponsiveness. This specific nonresponsiveness may be caused by the ability of the compound to be broken down by the body or by the route of administration of the compound n  Oral adminstration

 

 

Cells of the immune system
1.    B lymphocyte and T lymphocytes	Primary cells of specific immune responses. ANTIGEN-specific
Antigen Receptors of B-CELLS
Different B cells have different antigen specificities, but each B cell has ONE specificities n  B cells that recognize specific antigens divide to form new Bcells (memory B cells) and plasmacells (antibody-forming cells), which secrete free,soluble (humoral) antibody molecules into extracellular fluids   n  Virgin B cell have not responded to an antigen since their release into the circulation from bone marrow   Ø  Membrane antibodies:  IgM, IgD n  Memory B cells- derived by cell division from another B cell that has responded  to an antigen. Ø  Ig A, G,E
Antigen receptors of T-CELL
n  Have two (2) membrane proteins  (α and β or γ and δ),which define the antigen specifity of each T-cell and several other integral membrane proteins known as CD3 complex n  T-cells are CD3+   A.   Major Histocompability Complex *MHC) proteins. The antigens of Tcells do not recognize antigens alone. n  THEY NORMALLY RECOGNIZE PEPTIDE EPITOPES (fragment of antigens) that are  chemically combined with MHC proteins on the surface of other body cells à TWO MAJOR CLASSES 1.    Class 1 proteins- present on the surfaces of all body cells 2.    Class II proteins- present on the surface of special antigen-presenting cells APC B.    THYMUS GLAND Ø  T cells do not enter the circulation directly from bone marrow but first enter the thymus gland to mature. Most developing T-cells die in THYMUS. Ø  T-CELLS released from thymus into circulation= VIRGIN T CELL Ø  T-cells  that originate through cell division from the response of the other T cells are= MEMORY T CELLS or EFFECTOR T CELLS C.   GLYCOPROTEINS. Ø  T-cell classification by the presence of a membrane glycoprotein CD4—the helper or the presence of CD8 or the cytotoxic T cell. Ø  T-HELPER CELLS -          TH1 cells-activate other cells, including some TH cells, Tc cells and macrophages. Decrease ANTIBODY (Ab) production by inhibiting the formation of TH2cells -          TH2 cells- activate B cells and produce Ab. Inhibit formation of Th1 cells Ø  T-CYTOTOXIC CELLS -          Are able to KILL CELLS that are infected BY VIRUSES. Ø  T REGULATORY CELLS -          Most are CD4+ -          Suppress Immune response through the secretion of IL-10 and transforming growth factor B TGFB Ø  Cytokines

 

3.      NATURAL KILLER CELLS- large granular lymphocytes without specific T or Bcell antigen receptor. Their cytotoxicity is similar to that of CTL (Tc) cells.-

-          NK cells kills DESTROY TUMOR

-          Important in viral infections prior to dev’t adaptive immunity

4.      APC- essential for most immune response and are found in the sites at which these responses originate

a.     EX: MACROPHAGES, DENDRITIC CELLS

5.      Neutrophils, macrophages, eosinophils, basophils, platelets, and mast cells - -assist in ELIMINATING ANTIGENS FROM THE BODY.

FIVE CLASSES OF ANTIBODIES/IMMUNOGLOBULINS

1.      Ig M - first to be secreted during primary immune responses

-          Accounts 20% of the adult serum Ig

-          Can’t leave blood

-          MOST POTENT ACTIVATOR OF THE COMPLEMENT SYSTEM

2.    IgG – predominant serum immunoglobulin secreted at the end of primary immune response and during memory responses

-          can diffuse from blood into extracellular fluids; crosses placenta

-          Account 70% of adult Ig

-          OPSONIZES antigens for phagocytosis and activates the complement system

3.    Ig E – Binds to IgE receptors located on the cell surface, blood basophils ans on mucosal and connective tissue

-          To trigger secretion of inflammatory mediators

-          Mediates Allergic reaction

-          Less 1%

4.    Ig A- Secreted in large quantities across mucosal surfaces into GI, respiratory, lachrymal, mammary and genitourinary secretions, where it protects mucosa from colonization of bacteria and others

-          10%

5.    Ig D- NO KNOWN FUNCTION

-          less 1%

HYPERSENSITIVITY REACTIONS- exaggerated, inappropriate or prolonged immune responses that cause damage to otherwise normal tissue

FOUR TYPES

1.      Ig E mediated TYPE I- hypersecretion of IgE (tendency is heritable)

-          Does not usually occur on the first exposure to a specific allergen

-          TX:

o   Epinephrine Kits- reverses anaphylaxis

o   Competitive H1 antagonist

o   Cromolyn Na- inhibit mast cell degranulation

-          Note: Non- IgE mediated Type 1 reaction- anaphylactoid reaction

2.      TYPE II Hypersensitivity Reactions-  occurs through the production of Ig M and Ig G

-          Antigens: transfusion mismatches, Rh disease, drug allergens, autoimmune conditions

-          MAJOR SIGNS: Hemolytic anemia and thrombocytopenia

3.      TYPE 3 Reactions- persistence of immune complexes in the circulation or at local tissue sites when they are not removed after production of specific  antibodies ad antibody-antigen complexes

-          IMMUNE COMPLEXES ACTIVATE COMPLEMENT , cause  inflammation and induce positive chemotaxis in neutrophils.

-          SIGNS: Lymphadenopathy, splenomegaly, fever, rash

4.      Type IV Hypersensitivity reactions- prolonged inappropriate and appropriate immune responses mediated by ANTIGEN-SPECIFIC TH1 cells in concert with activated macrophages

-          Tuberculin test (Mantoux reaction)

-          Common antigens: Mycobacterium tb. M. leprae, Listeria monocytogenes