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ability of a parasite to penetrate tissues and cause structural damage; type of virulence factor
microbial poisons that affect the establishment and course of disease by increasing microbe's virulence
two types of toxins:
exotoxins and endotoxins
- protein molecules, manufactured mainly G+ bacteria, produced by botulism organism, clostridium botulinum.
- inhibits release of neurotransmitter called acetylocholine at junction where nerve cells meet muscle cells; inhibition leads to paralysis
body's response to exotoxins?
special antibodies called antitoxins
combines with toxin and neutralizes it
an altered toxin, where chemical agent used to alter the toxi nand destroy its toxicity
toxoid molecules used as?
vaccines to protect against diphtheria and tetanus
part of cell wall of G- bacteria and released only on disintegration of cell
endotoxins manifest itself by...
certain signs and symtoms such as increased body temp, body weakness and aches, and general malaise
damage to circulatory system and shock occur
nonspecific resistance to disease, affected by these determinants..
nutrtion, fatigue, age, sex, and climate
form of nonspecific resistance that means the diseases affecting one species will not affect another
poor source of carbon for microbes
the skins have these...
sweat and fatty acids in sebum that contain antimicrobial agents and low water content make its veritable desert
form of nonspecific resistantce in body
cells involved in phagocytosis called?
phagocytes are large cells that originate in bone marrow, circulte in bloodstream, then leave circulation, and develop in tissues
highly specialized phagocytes
- found in spleen, bone marrow, lymph nodes, and brain
what happens when a macrophage encounter a microbe?
- encloses microbes with cell membrane, infolds membrane to form phagocytic vesicle or phagosome.
- then pinches off and fuse with lysosome
- -bacterium disintegrates thru activity of lysosomal enzymes
nonspecific defensive response that occurs when irritant such as microbe is present
irritant sets to motion and limits extent of injury [dilation of blood vessels increases flow of blood at site of irritation]
signs of inflammation.
- rubor [red color from blood accumulation]
- calor [warmth from heat of blood]
- tumor [swelling]
- dolor [pain from injury to local nerves]
- chemical substances capable of stimulating immune system and provoking immune response
- -large, complex molecules, not normally found in body and refer to 'nonself'
- -milk proteins, bee venom proteins, hemoglobin molecules, baccterial toxins, and chemical substance found in microbial flagella, pili, and cytoplasm
most common antigens=
- proteins and polysaccharides,
- lipids and nucleic acids can be antigens
proteins are potent antigens
cuz amino acids represent a great array of bilding blocks, allowing for huge variety of combinations
antigens easily phagocytized by..
- antigen itself doesnt stimulate immune system, but by antigen molecule called antigenic determinant (or epitope)
contains 6-8 amino acid molecules or monosaccharide units
- cornerstones of immune system
- -distributed thru-out body and comprise organs of lymphoid system, includes lymph nodes, spleen, tonsils, and adenoids
- -small cells, each with large nucleus
two types of lymphocytes
- -B lymphocytes (B cells)
- -T lymphocytes (T cells)
B cells responsible for
T cells are responsible for
- from stem cells [primitive cells in yolk sac and bone marrow]
- stem cells develop to lymphopoietic cells, which take on two paths
whats the two path that lymphopoietic cell will take?
- 1. move to thymus, then modified by addition of suface receptor proteins or destroyed. destoryed ones are one's that respond to self. modified lympopoietic cells emerge as T cells
- 2. B cells . mature in site that has not been determined with certainty in humans. in embryonic chick, site idenitified as bursa of Fabricius
B cells mature...
with surface receptor proteins on membranes and become immunocompetent. move thru circulatory system to coloize organs of lymphoid system, where join T cells
surface receptor proteins
enable B cells and T cells to recognize specific antigenic determinant and bind to it
surface recptor proteins in B cells? T cells?
- B cells- antibody molecule, called IgD
- T cell - composed of two chains linked one another
B cell and T cell oversees...
- B cell - bacteria and viruses
- T-cell - fungi and protozoa
cell-mediated immunity CMI
body's ability to resist infection thru activity of T-lymphocyte recognition of antigen peptides presented on macophages and dendritic cells and on infected cells
major histocompatibility proteins (MHC proteins)
macrophage have these that must match with MHC receptors on surface of T-cell
match up with MHC completed, ...
inactived T-cells assume to activated form, cytotoxic T cell. transition acquires help of helper T cell . antigenic determinants and MHC protein must match with helper T cell. (CD4 receptor)
helpter T cell after attachment...
multiplies and clones and secretes highly charged proteins aka lymphokines[aka cytokines]
stimulate cytotoxic T cells to enlarge and divide, yeild host of cells capable of killing infected cells
Cytotoxic T cells travels..
leave lymphoid tissues to lymph and blood vessels seeking infect individuals, finds them and releases number of active substances, include toxic protein called perforin
toxic protein inserts to membrane of microbes or infecte cell and dissolves it.
cytotoxic T cell releases
lymphokines, which are glycoprotein molecules used to enhance defensive capabilities of body
third lymphokine that mobilizes other T cells in area and encourages their conversion to cytotoxic cells
memory T cells
type of T cells form in lymphoid tissues that provide resistance to the event which the pathogen reenters body in future.
antibody-mediated immunity AMI
aka humoral immune response. immune reaction of producing antibodies directed against antigens in body fluids
antibodies react with toxin molecules in bloodstream, also with microbial antigens and wiht viruses in body fluid
once B cells activated,
multiply rapidly, developing to plasma cells
plama cells are...
large, complex cells having no suface protein receptors, sole purpose is to produce antibodies. and antibody molecules fill the blood, lymph, saliva, sweat, and all body secretions
some B cells do not become plasma cells but...
memory B cells
memory B cells-
remain in lymphoid tissues for years, should antigens reenter body, memory cells will revert to plasma cellsa nd produce antibodies wihout delay
structure of antibodies.
consists of 4 polypeptide chains: 2 identical heavy (H) chains and two identical light (L) chains. joined together by chemical linkages to form Y-shaped
polypeptide chain -
- both have constant and variable regions
- constant regions - amino acids identical among differ types of antibodies
- variable regions - amino acids differ of antibody types
- -Susumu Tonegawa
- -incalculable number of gene combinations acct for variety of antibody moelcules body produces
5 differ types of antibodies.
- - IgM,
- - IgG
- - IgA,
- - IgE,
first type of antibody to appear in circulatory system after B cell stimulation, the largest
- gamma globulin
- major circulating one,
- appears about 24-48 hours after antigenic stimulationg and cont the antigen-antibody interaction begun by igM
- provides long0term resistance to disease
- maternal antibody that crosses placenta and renders immunity to child
- serum IgA
- -second form of IgA accumulates in body secretions aka secretory IgA
- -provides resistance in respiratory & gastrointestinal tracts, by inhit attachment of parasites to tissues
- -located in tears and saliva in colostrum, first milk secreted by mothers
- -consumed by child, provides resistance to gastrointestinal disordres
in allergic reactions by sensitizing cells to certain antigens
- membrane antibody - cell surface receptor on B cells
- functions and significance - unclear
interacts till the antigen is altered resulting in death of microbes with the antigen.
other antibodies react with antigens on surface of bacteria. action causes clumping (agglutination) of microbes and enchances phagocytosis
antibodies that react with dissolved antigens and conert them to soild precipitates, this form of antiges are usually inactive and more easily phagocytized
antigen-antibody interaction involving complement system
- by Jules Bordet
- -complement system is a series of over 20 proteins that function in cascading set of reactions. set into motion by interaction of antigen and antibody molecules
- -takes place on surface of cell
- -increases permeability of cell membrane and induces cell to undergo lysis thru leakage of lfiud from cytoplasm
type types of immunity.
- -innate immunity
- -acquired immunity
inborn capacity for resisting disease
- depends on acitivity of T cells, antibodies, and other factors originating in immune system.
- -an active and a passive immunity
- if it develops when immune system responds to antigens and forms antibodies
- -takes several hours or day to develop, but remains for long period of time
- if it develops when antibodies enter body from otuside source
- -comes immediately when antibodies enter body, last only weeks
active and passive further subdivided to 4 types.
- 1. naturally acquired active immunity
- 2. artificially acquired active immunity
- 3. naturally acquired passive immunity
- 4. artificially acquired passive immunity
naturally acquired active immunity
- follows a bout of illness
- Memory T or B cells reside in lymphoid tisses remain active for year and produce IgG immediately if pathogen enters
artificially acquired active immunity
- develops after exposure to antigens in vaccine
- -antigens may be toxoids, inactivated ciruses, synthetic viral parts, bacteria parts or other compents
- -vaccines promote long-term immune response in form of memory T or B cells and IgG antibodies
naturally acquired passive immunity
- aka congential immunity
- -develops when IgG antibodies pass from mother's bloodstream to fetal circulation via placenta and umbilical cord
- -stays with child 3-6 months and fades as child's own immune system kicks in.
artificially acquired passive immunity
- arises from injection of antibody-rich serum into circulation
- -form of therapy is used for serious viral diseases and toxin-related disease such as botulism and tetanus
- -serum injected aka gamma globulin
- -injections sometimes seen as foreigners by body