ch. 43 part 2 Flashcards
cytokines are released from the ________ to activate the helper T cell
macrophage/dendritic cell
activation of B cell in humoral response
- entered antigen taken in by receptor-mediated endocytosis
- MHC 2 presents antigen on B cell surface
- activated helper T cell recognizes antigen and releases cytokines
- activated B cell divides into memory and plasma cells
plasma B cells
secrete antibodies that go out and identify/mark foreign pathogen
how many antibodies does each plasma cell release
over a trillion over 4-5 days
- 2,000 per second
what do antibodies do
mark pathogens for inactivation/destruction
- don’t kill them
3 processes performed by antigens
- neutralization
- opsonization
- antigen-antibody complex
- agglutination
- precipitation
neutralization
antibodies bind to viral surface proteins, preventing infection of a host cell
opsonization
antibodies bind to antigens on bacteria, triggering phagocytosis
positive feedback system of opsonization
- dendritic cells/macrophages present antigens on surface to become antigen-presenting cells
- stimulates humoral immunity
- opsonization enhances antigen presentation and humoral immunity
antigen-antibody complexes
may bind to complement protein, which triggers cascade of complement protein activation to form membrane attack complex
membrane attack complex
forms pore in the membrane of the foreign cells, leading to its lysis
how can humoral immunity kill infected cells
- viral infected cells often display part of virus on infected cell surface
- if antibodies specific for epitopes on these viral fragments, they bind to viral proteins
- natural killer cells induce infected cells to undergo apoptosis
agglutination
antibodies often have 2 receptor sites for antigens on pathogens, and binds to 2 antigens. this creates a clump, which is easier to engulf by macrophages
precipitation
binds to free-floating antigens and clumps them together, which are then engulfed by macrophage
how many different forms/classes of immunoglobulins can B cells express
5
different forms of immunoglobulins
- similar antigen-binding specificity
- different heavy chain C regions
- IgD is membrane bound
- IgA, IgE, IgG, and IgM are soluble
cytotoxic T cells
use toxic proteins to kill cells infected by viruses or other intracellular pathogens
what do cytotoxic T cells recognize
fragments of foreign proteins produced by infected cells
what does an activated cytotoxic T cell secrete
proteins that disrupt membranes of target cells and trigger apoptosis
CD8 protein function
between cytotoxic T cell and virus-infected cell, determines if infected cell needs to be killed or not
- helps recognize if class I MHC
what does cytokines interleukin 2 do
stimulates production of specialized helper T cells and cytotoxic T cells to eliminate threat
what tells the cytotoxic T cell to kill an infected cell
signal from helper T cell attached to macrophage
what is released in the gap between the cytotoxic T cell and infected cell
vesicles containing perforins
what do perforins do
create channels that allow water to rush into the cell
how are viruses eliminated
through humoral response (antibodies/opsonization) and through cell-mediated cytotoxic response
basis of immunization
projection provided by second immune response
why are antigens artificially introduced into the body?
to generate adaptive immune response and memory cell formation
how are immunizations carried out
vaccines - preparations of antigens from many sources
active immunity
develops naturally when a pathogen invades the body and elicits a primary or secondary immune response
- actually exposed to antigen
passive immunity
provides immediate, short-term protection
- conferred naturally when IgG crosses placenta from mother to fetus or when IgA passes from mother to infant in breast milk
ex. of natural active immunity
infection
ex. of artificial active immunity
vaccination
ex. of natural passive immunity
maternal antibodies
ex. of artificial passive immunity
monoclonal antibodies
- antibodies from immune animal injected into a non immune animal
what are antibodies produced by an animal after exposure to an antigen products of
different clones of plasma cells
monoclonal antibodies
can be prepared from single clone of B cells grown in culture
- identical
- specific for 1 epitope
- used in many types of medical diagnoses
why are blood transfusions and tissue transplants sometimes complicated?
cells transferred from one person to another can be attacked by immune defenses
what is done to minimize rejection of a transplant or graft?
- use donor tissue with MHC molecules as similar as possible to the recipient
- recipient takes medicines that suppress immune responses
antigens on red blood cells
- A - A antigen
- B - B antigen
- AB - A and B antigens
- O - neither antigen
what kind of blood antibodies exist in the body
antibodies to non self blood types
allergies
hypersensitive (exaggerated) responses to antigens called allergens
localized allergies
- IgE antibodies produced after first exposure to allergen attach to receptors on mast cells
- next time allergen enters body, it binds to mast-cell-associated IgE molecules
- mast cells release histamine/inflammatory chemicals that bring about typical allergy symptoms
acute allergic response
can lead to anaphylactic shock within seconds of allergen exposure
anaphylactic shock
life-threatening reaction
what can counteract an allergic response
injection of epinephrine
autoimmune disease
immune system loses tolerance for self and turns against certain molecules of body
ex. of autoimmune diseases
- lupus erythematosus
- rheumatoid arthritis
- insulin-dependent diabetes mellitus
- multiple sclerosis
exercise and immune system function
- moderate - improves function
- exhaustion - leads to frequent infections
effect of psychological stress on immune system
disrupts it by altering interactions of hormonal, nervous, and immune systems
inborn immunodeficiency diseases
result from genetic or developmental defect in innate/adaptive defenses
acquired immunodeficiency diseases
develops later in life due to exposure to chemical/biological agents
how are some pathogens able to prevent recognition
change epitope expression through antigenic variation
human influenza virus
- mutates rapidly
- new flu vaccines made each year
what do human viruses often exchange genes with?
viruses of domesticated animals
- human immune systems then unable to recognize new viral strain
latency
inactivate state of some viruses in a host
herpes simplex viruses
can be present in a human host without causing symptoms
human immunodeficiency virus (HIV)
- infects helper T cells
- high mutation rate that promotes antigen variation - persists in host
what happens over time to untreated HIV infection
avoids adaptive immune response and abolishes it
what does HIV infection lead to
acquired immunodeficiency syndrome (AIDS)
AIDS symptoms
highly susceptible to opportunistic infections and cancers that a normal immune system would usually defeat
how does the frequency of certain cancers increase
when adaptive immunity is inactivated
what percent of human cancers involve viruses
15-20%
what is human papilloma virus associated with
cervical cancer
