Chapter 43: Immune System Flashcards
Pathogens
foreign invaders that try to co-opt organismal resources; cause disease
immune system
necessary to avoid/limit infection
innate immunity
active all the time, non-specific. Found in all animals and plants
acquired immunity
adaptive immunity; enhanced by previous infection, highly specific. Found in vertebrates
barrier defenses
skin, mucous membranes, secretions
Internal defenses
phagocytic cells, natural killer cells, antimicrobial proteins, inflammatory response
humoral response
antibodies defend against infection in body fluids
cell-mediated response
cytotoxic cells defend against infection in body cells
innate immunity in insects
barrier: waxy chitin exoskeleton
low pH and lysozyme: digest microbes in gut
hemocytes in hemolymph: phagocytosis and various chemical protections
antimicrobial peptides: disrupt pathogen plasma membrane
innate immunity in vertebrates
barrier: skin epithelium, mucus coverings over exchange surfaces
lysozyme in saliva, mucus, teats, etc.
sweat lowers skin pH, low stomach pH
toll-like receptors
Toll-like receptor (TLR)
receptors that recognize pathogen bits
macrophages
white blood cell; phagocytosis engulf and digest microbes
interferons
antimicrobial peptide; produced by cells infected by viruses, signal other cells to produce anti-viral compounds
complement system
antimicrobial peptide; activated by microbial substances, leads to bursting of cells
lymphatic system
organs to trap foreign particles; tonsils, spleen, appendix
inflammatory response
release of signaling molecules following infection/injury; causes warmth, swelling, formation of pus
mast cells
release histamine; causes vessels to dilate, become more permeable
pyrogens
part of systemic inflammatory response; causes localized increase in temperature
natural killer cells
can recognize and destroy diseased cells; look for cells that do not produce class I MHC surface proteins and kill them
lymphocytes
white blood cells; have an enhanced response to infections the body has previously encountered (immunological memory)
B-cells
type of lymphocyte; mature in bone marrow. secrete soluble receptors (antibodies) that bind to foreign molecules
T-cells
type of lymphocyte; move from bone to the thymus. detect and kill infected cells or help activate other lymphocytes
immunological memory
lymphocytes activate by binding to specific foreign molecule as a response to infections previously encountered
antibodies
soluble antigen receptors from b-cells
antigens
foreign molecules recognized by lymphocytes; small molecules, parts of large molecules; may be on the surface of pathogens
antigen receptors
receptors in plasma membrane of T & B lymphocytes
plasma cells
some B lymphocytes that produce soluble antigen receptors (antibodies)
epitope
small part of antigen that is recognized by antigen receptor
b-cell antigen receptor structure
Y- shaped, two identical heavy chains, 2 identical light changs. each chain has constant (C) and variable (V) regions
T-cell receptor structure
alpha and beta chains, constant (C) and variable (V) regions but with 1 antigen binding site
MHC
major histocompatibility complex; make proteins that present antigens on cell surface
Class I MHC
in almost all cells; bind foreign peptides synthesized in cell, recognized by cytotoxic T cells
Class II MHC
in macrophages, B cells, etc (antigen presenting cells), bind foreign fragments acquired through phagocytosis; recognized by helper T cells
light chain
composed of 3 regions: variable, joining, constant
recombinase
enzyme randomly links a variable to a joining region, increasing variability/options
heavy chain
similar to a light chain, but with even more options; variable, joining, and constant regions
self tolerance
the self-reactivity of a lymphocyte
clonal selection
division of B cells into many memory b cells and plasma cells
effector cells
type of daughter cell; short lived, attack antigen/pathogen
memory cells
type of daughter cell; long lived, with same antigen receptor
humoral immune response
activation and clonal selection of effector B cells; secrete antibodies that circulate in blood and lymph
primary immune response
first exposure; production of plasma cells and memory cells which leads to immunological memory
secondary immune response
second exposure; faster response, relies on increased numbers after first exposure
helper T-cells
enhance humoral and cell-mediated responses; stimulates B cells and cytotoxic T cells
cytotoxic T-cells
effector T cells; secretes proteins that rupture cell membrane
activation of B cells
requires interaction with helper T cells
neutralization
antibodies bind to virus, bacterium or toxin to interfere with pathogen function
opsonization
binding sites for macrophages on pathogen
complement proteins
form ‘membrane attack complex’
vaccination
introduction of antigens to build immunity
passive immunization
antibodies passed from mother to fetus
artificial passive immunization
inject antibodies directtly
blood groups interaction
different blood groups make different antigens; ie. if type A person gets B blood, B antigen lymphocytes will attack them
tissue rejection
transplanted tissues make foreign MHC proteins; targeted by immune response
allergies
hypersensitive response to antigens, results in inflammation
autoimmune diseases
diseases caused by immune system turning against the body
immunodeficiency
lowered effectiveness of immune system
antigenic variation
pathogens change in epitope expression to thwart immunological memory
latency
some viruses persist without making viral particles
HIV (human immunodeficiency virus)
causes AIDS; both evades and damages immune system
