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Concept Dis. Ch 5

Immunity, Hypersensitivity, Allergy & Autoimmune Diseases

defense mechanisms for dealing w/pathogenic microorganisms & other harmful substances inflammatory response & acquired immunity
nonspecific response to any harmful agent, includes phagocytosis by neutrophils & macrophages inflammatory reaction
develops after contact with pathogenic defense mechanisms for dealing w/pathogenic microorganisms & is capacity to react to lrg # of foreign antigens acquired immunity
humoral & cell-mediated immunity are the 2 types of acquired immunity
humoral immunity assoc w/production of antibodies that can combine w/& eliminate forge in material(s)
humoral immunity is body's major defense against many bacteria & bacterial toxins
cell-mediated immunity characterized by formation of population of lymphocytes to attack/destroy foreign material
cell-mediated immunity is a mechanism by which body rejects transplanted organs & eliminates abnormal cells arising during cell division
acquired immunity is often associated w/stage of altered reactivity to bacterial products/foreign material leading to intense inflammatory reaction at site of contact w/antigen
hypersensitivity state of abnormal reactivity to a foreign material
person who displays hypersensitivity to antigen/its products usually possesses some degree of immunity as well
many disease are associated w/development of an acquired immunity without being capable of demonstrating hypersensitivity
normally people develop immune response to non-self antigens
lymphocytes accidentally programmed to react to self-antigen, during prenatal development are destroyed/inactivated suppressing their function
autoantibodies antibody formed against one's own cells/tissue components
autoimmune diseases associated with formation of cell-mediated or humoral immunity against one's own cells or tissue components
when our immune system attacks us it produces groups of destructive lymphocytes & injurious antibodies directed against own cells/tissues
autoimmune disease can cause considerable organ/tissue damage
important cells of immune system that respond to foreign antigens are lymphocytes and macrophages/related cells that process antigen & present to lymphocytes
immune system cells communicate & product their effect by secreting soluble peptide(protein) messengers
lymphokines soluble substance (cytokine) liberated by lymphocytes
cytokines gen. term for any protein secreted by cells that functions as intercellular messenger, influencing cells of immune system
secreted by macrophages & monocytes, lymphocytes & other cells cytokines
monokines soluble substance (cytokine) liberated by monocytes
interferons broad-spectrum antiviral agent manufactured by various cells in body
interleukins chemical messenger that sends regulatory signals between cells of immune system
Interleukin-2 lymphokine stimulating growth of lymphocytes
tumor necrosis factors cytokine that can destroy foreign/abnormal cells
named because they can destroy tumor cells, by functions not restricted to only tumor cells tumor necrosis factors
precursor cells of lymphocytes are initially formed from stem cells in bone marrow
development of lymphocytes into their two groups depends on where they undergo further development & "learn" their functions
where they undergo further development & "learn" their functions is a process called developing immune competence
precursor cells that migrate to thymus for maturation/development into cells forming a specific lymphocyte called T (thymus-dependent) lymphocytes
T lymphocytes are a type of lymphocyte associated with cell-mediated immunity
lymphoid cells remaining within bone marrow to differentiate & develop are destined to become B (bone-marrow) lymphocytes
B lymphocytes are a lymphocyte that differentiates into plasma cells
B lymphocytes are associated with humoral immunity
rearrangement of genes within developing B & T lymphocytes is programming process by which lymphocytes acquire immune competence
antigen receptors of B lymphocytes are immunoglobulin molecules
immunoglobulins are antibodies
T lymphocyte receptors develop differently but serve same functions as those on B cells
single lymphocyte can respond to only a single antigen
before birth B&T cells migrate and proliferate to form masses of mature lymphocytes in the spleen, lymph nodes & other lymphoid sites
CD (cluster of differentiation) antigens classify T cells into 2 groups based on protein molecules
lymphocytes containing CD4 antigens are called T4 lymphocytes
lymphocytes containing CD8 antigens are called T8 lymphocytes
lymphocytes do not remain localized, they continually re-circulate btwn bloodstream & various lymphoid tissues
___ of circulating lymphocytes are T lymphocytes 2/3
natural killer cells (NK cells) lymphocytes capable of destroying foreign or abnormal cells without prior contact w/cells
major targets of NK cells are cancer cells & virus-infected cells
destroy target cells as soon as encountered, by secreting destructive lymphokines NK cells
NK cells are on related to, but not part of, cell-mediated immunity because they activate & function more effectively when stimulated by lymphokines secreted by T cells
NK cells are on related to, but not part of, humoral immunity because some types possess cell membrane receptors for antibody molecules, making it easier to attach/destroy target cells coated w/antibodies
macrophages are monocytes that have left bloodstream to take-up residence in tissues throughout body where they phagocytose & process antigens
dendric cells widely distributed cells that process antigens & present to lymphocytes
T lymphocytes can only respond to processed antigens
B lymphocytes can respond to intact antigens by processing them & display antigen fragments on their cell membranes
first step in acquired immune reaction is recognition of foreign antigen
second step in acquired immune reaction is proliferation of lymphocytes programmed to respond to antigen, forming larger group of cells
cells formed in response to an antigen during second step in acquired immune reaction are clone cells
third step in acquired immune reaction is destruction of antigen by lymphocytes responding to antigen
epitopes small fragment of antigen displayed on cell membrane of antigen processing cell
antigenic determinants is another name for epitopes
when appropriately stimulated B lymphocytes proliferate & mature into antibody-forming plasma cells
when appropriately stimulated T lymphocytes proliferate forming diverse population of cells to regulate immune response & generate cell-mediated immune reaction to eliminate antigenic material
after initial contact with an antigen there is a lag phase of week/more before immune response is demonstrated
lag phase corresponds to time required for processing antigen & for lymphocytes to respond
some lymphoid cells retain a memory of foreign antigen that induced sensitization
later contact with the antigen provokes renewed proliferation of sensitized lymphocytes or antibody-forming plasma cells
main function of major histocompatibility (MHC) protein is to serve as carrier for processed foreign antigen fragments on the surface of cells to generate immune response
immune system response depends primarily on lymphocytes & antigen-producing cells
type of T cells attack and destroy infected cells cytotoxic
delayed hypersensitivity cells help suppress infections by attracting macrophages, cytotoxic T cells and NK cells
immunoglobulin that forms a complex pentamer is IgM
Immunoglobulins contain how many light chains? two
hypersensitivity reaction characterized by complement-activated & cell-tissue injury Immune Complex Disease & Cytotoxic Hypersensitivity
situations might make immune system suppression desirable development of autoimmune disease, organ transplantation, & Rh hemolytic disease
method of immune system suppression that works primarily by destroying normal cells including lymphocytes is radiation
Grafting of foreign tissue can provoke an immune response because the tissue contains HLA antigens
autoimmune diseases of the connective tissues are characterized by necrosis & degeneration of fibrous connective tissue
in response to displayed antigen-MHC Class II proteins by macrophage-like antigen processing cell T cells having corresponding antigen receptors proliferate & form clone group of identical T cells
macrophages are activated when they process & present antigen to T cells
macrophages secrete a cytokine that stimulates T cells to proliferate
B lymphocytes have immunoglobulin molecules on their cell membranes functioning as antigen receptors
the 2 major groups of T cells, regulator and effector T cells, function together to regulate immune response & act against foreign antigens
regulator T cells are T4 (CD4+) cells
T4 (CD4+) cells function as helper & suppressor T cells
helper T cells promote immune response by secreting cytokines that activate effector T cells & B cells
suppressor T cells promote immune response by producing cytokines to inhibit excessive immune system stimulation
inhibits immune response & increases vulnerability to infection, i.e. AIDS loss/destruction of helper T cells
cytotoxic & delayed hypersensitivity T cells are the two types of effector T cells
T8 (CD8+) produce cytokines that destroy foreign/abnormal cells displaying antigen fragments combined with MHC Class I antigens cytotoxic T cells
T4 (CD4+) respond to antigen processing cells presenting foreign antigen fragments combined w/MHC Class II antigens delayed hypersensitivity T cells
delayed hypersensitivity T cells produce cytokines that activate & stimulate macrophages, cytotoxic T cells, & NK cells
delayed hypersensitivity T cells stimulate macrophages to secrete interferon & TNF
NK cells destroy virus infected cells & cancer cells through cytokine-mediated cell destruction with no prior contact with antigen required
immune response genes genes on chromosome 6 that control immune response to specific antigens
immune response genes regulate T & B cell proliferation in order to regulate intensity of cell-mediated immune reaction & synthesis of antibody molecules
immune response genes influence likelihood of acquiring autoimmune disease
classical pathway of complement activation triggered by antigen-antibody interactions
alternate pathway of complement activation triggered by bacterial cell wall material/products generated during inflammatory reactions
complement components interact to mediate inflammation, coat surface of invading bacteria, & generate attack complex
attack complex destroys target microorganism/abnormal cell by "punching holes" in cell membrane
immunoglobulins antibody protein
immunoglobulins differ in size, chemical composition & molecular weight bit all have same basic structure of 2 matched pairs of polypeptide chains joined by chemical bonds
variable part of the Ig molecule is the "prong" end of the molecule, which is different in each antibody
immunoglobulins can only react with specific antigen that induces its formation
the "handle" end of the Ig molecule does not combine with antigen by determines other properties of antibody, such as ability to activate complement or fix to surface of cell membrane
IgM four-chain unit structure usually consists of a cluster of five individual units
IgA four-chain unit structure usually consists of a pair of units
antibody molecule junction of its constant & variable parts is flexible, called hinged region
hinge region allows variable end of Y-shaped molecule to adapt to configuration of antigen that it is binding
enzyme treatment of Ig breaks a molecule into three fragments
variable region of Ig molecule treated with enzyme yields two fragments called Fab fragments, antibody combining fragment
antibody combining fragment consists of light chain & associated part of the heavy chain
after enzyme treatment the corresponding fragment, to Fab, is constant region of molecule, called Fc fragment/constant fragment
IgM forms a large cluster efficient in combining with large particle antigens, such as fungi
IgM is often called a macroglobulin because of its large size & high molecular weight
IgM molecules can also be found as monomeric molecules attached to cell membrane surface of B lymphocytes functioning as antigen receptors
IgG is the principle type of antibody molecule formed in response of infectious agents
IgA produced by antibody-forming cells located in respiratory & gastrointestinal mucosa & present in secretions of both
functions by forming antigen-antibody complexes that cannot be absorbed preventing antigens from inducing sensitization
found in cell membranes of B lymphocytes & present in minute quantities in blood IgD
present in small quantities of normal individuals blood, but concentrated in allergic individuals IgE
immunity resistance to disease
hypersensitivity state of abnormal reactivity to foreign material
I: immediate hypersensitivity IgE fix to mast cells & basophils; later contact w/antigen triggers mediator release & clinical manifestations
II: cytotoxic hypersensitivity reactions antibody binds to cell/tissue antigen, complement activated damaging cells, causing inflammation & destruction antibody-coated cell by phagocytosis
III: immune complex disease circulating antigen-antibody complexes form, activating complement & causing inflammatory reaction
IV: delayed (cell-mediated) hypersensitivity sensitized T cells release lymphokines attracting macrophages & other inflammatory cells
localized response: hay fever, food allergy; systemic response: bee sting anaphylaxis I: immediate hypersensitivity
lupus erythematosus, RA, some types glomerulonephritis III: immune complex disease
tuberculosis, fungus/parasitic infections, contact dermatitis IV: delayed (cell-mediated) hypersensitivity
anaphylaxis severe generalized IgE-mediated hypersensitivity reaction characterized by marked respiratory distress & fall in BP
atopic person genetic predisposition to certain allergic conditions
allergen substance capable of inducing allergic reaction in predisposed individual
desensitization method of inducing diminished response to allergens by inducing formation of specific IgG & IgA antibodies
anaphylactoid reaction hypersensitivity reaction resembling anaphylaxis but not caused by IgE antibodies
in Type I reaction IgE attaches to cell membrane by means of Fc end (handle of fork) of molecule
in Type I reaction, upon 2nd exposure to sensitizing antigen, the antigen attaches to free antibody combining sites (prongs of fork) on IgE molecules
in Type I reaction union of antigen & antibody cause cells to release cytoplasmic granules filled w/histamine, prostaglandins & other potent chemical mediators
in Type I localized reactions are called allergic reactions
in Type I systemic reactions are called anaphylaxis
in an allergy the allergic manifestations are localized to tissues exposed to allergens
desensitization induces formation of specific IgG & IgA antibodies which act by combining w/allergen before can affix to cell-bound IgE & trigger release of mediators
prompt treatment with epinephrine & other appropriate agent is essential anaphylaxis reaction
Mantoux skin test is used to detect infection w/tubercle bacillus based on presence or absence of delayed hypersensitivity reaction to proteins of tubercle bacillus
only indicates prior infection w/organism & development of cell-mediated immunity; not indicative of active tuberculosis Mantoux skin test
radiation, immunosuppressive drugs impeding cell division/function, adrenal corticosteroid hormones, & immunoglobulin preparations are main types of immunosuppressive agents commonly used by physicians
exerts immunosuppressive effect by destroying lymphoid tissue radiation
cytotoxic drugs act by suppressing growth & division of lymphocytes
cytotoxic producing cell necrosis or destruction
lymphoid tissue is especially susceptible to inhibitory effects of cytotoxic drugs
antimetabolites substance that competes with or replaces another substance (metabolite) required for cell growth/multiplication
cyclosporine suppresses immune system in patient's receiving organ transplant
suppress inflammatory response, impair phagocytosis and inhibit protein synthesis corticosteroids
act by interfering with generation of cytotoxic T cells, cytokines & autoantibodies injections of immunoglobulins
rejection immunologic process characterized by destruction of transplanted organ
certain HLA types appear to be associated with an increased susceptibility to specific autoimmune diseases
many autoimmune diseases occur more frequently in women
infection in person w/chronic autoimmune disease may cause flare-ups of disease
manifestations of autoimmune disease depend on which cells/tissue components are targeted for attack by the immune system
autoantibody-associated tissue injury results when antibodies become attached to cell membrane of target cells, activating complement-mediated destruction, assisted by activated macrophages & killer lymphocytes
antigen & antibody may combine to form immune complexes deposited in tissues & induce type of complement-mediated tissue injury
cell-mediated destruction of target tissues is caused by sensitized T lymphocytes that secrete lymphokines, which generate destructive inflammatory reaction in target tissue/organ
instead of destroying target tissues, sometimes autoantibodies derange function of target
group of diseases characterized by necrosis & degeneration of collagen fibers throughout body connective-tissue/collagen diseases
Created by: lfrancois