micro ch 17

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

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

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

vaccines to protect against diphtheria and tetanus

part of cell wall of G- bacteria and released only on disintegration of cell

certain signs and symtoms such as increased body temp, body weakness and aches, and general malaise

damage to circulatory system and shock occur

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

sweat and fatty acids in sebum that contain antimicrobial agents and low water content make its veritable desert

phagocytosis

form of nonspecific resistantce in body

phagocytes are large cells that originate in bone marrow, circulte in bloodstream, then leave circulation, and develop in tissues

• macrophages;
• found in spleen, bone marrow, lymph nodes, and brain

• 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

inflammation

irritant sets to motion and limits extent of injury [dilation of blood vessels increases flow of blood at site of irritation]

• 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

• proteins and polysaccharides,
• lipids and nucleic acids can be antigens

cuz amino acids represent a great array of bilding blocks, allowing for huge variety of combinations

• macrophages
• 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

• -B lymphocytes (B cells)
• -T lymphocytes (T cells)

antibody-mediated immunity

cell-mediated immunity

• from stem cells [primitive cells in yolk sac and bone marrow]
• stem cells develop to lymphopoietic cells, which take on two paths

• 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

with surface receptor proteins on membranes and become immunocompetent. move thru circulatory system to coloize organs of lymphoid system, where join T cells

enable B cells and T cells to recognize specific antigenic determinant and bind to it

• B cells- antibody molecule, called IgD
• T cell - composed of two chains linked one another

• B cell - bacteria and viruses
• T-cell - fungi and protozoa

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

macrophage have these that must match with MHC receptors on surface of T-cell

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)

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

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.

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

type of T cells form in lymphoid tissues that provide resistance to the event which the pathogen reenters body in future.

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

multiply rapidly, developing to plasma cells

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

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

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

• 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

• - IgM,
• - IgG
• - IgA,
• - IgE,
• -IgD

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

• 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

• -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

• 1. naturally acquired active immunity
• 2. artificially acquired active immunity
• 3. naturally acquired passive immunity
• 4. artificially acquired passive 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

• 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

• 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.

• 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