Immune System Flashcards
what are the functions of the immune system
- surveillance of the body
- recognition of foreign material
-destruction of entities deemed to be foreign
what is innate/natural/non-specific immunity stimulated by
-structures common to groups of related microbes
-cannot distinguish between fine differences of foreign substances
what is acquired immunity
- very specific response to a distinct macromolecule
- remembers macromolecules and response more vigorously the second exposure
what is the relationship between the innate immune system and acquire immunity
influence each other
what are the agranulocytes
-monocytes/macrophages
-lymphocytes
what are the granulocytes
-neutrophils
-eosinophils
-basophils
what is the order of abundance of blood cells
- neutrophils
- lymphocytes
-monocytes
-eosinophils
-basophils
describe the leukocytes compared to RBCs
all are nucleated and are larger and less numerous
describe all granulocytes
polymorphonuclear
what is the function of innate immunity
-protective
- neutralizes harmful agents
-removes dead tissue
- initiates the tissue repair process
what do damaged cells in innate immunity release and do
release inflammatory mediators which stimulate the inflammatory process but they can also injure normal tissue
where do mediators of the innate immune system act
locally and systemically
what are the cardinal signs of acute inflammation
-rubor
- calor (heat)
- dolor (pain)
- swelling
-loss of function
- edema
what is activated in the complement system
C3a and C5a
what do C3a, C5a, histamine, bradykinin, and serotonin cause
-fluid leakage as exudate
-vasodilation
what do neutrophils cause
-chemokines -> ingestion of bacteria -> cytokine secretion -> recruitment of macrophages and lymphocytes -> selectins -> endothelial stickiness and integrins
what is phagocytosis an essential part of
inflammation and acquired immunity
what particles do cells engulf
non-self or damaged particles
what is phagocytosis of innate immunity accomplished by
mostly neutrophils and macrophages
what is the difference in ability to phagocytize between macrophages and neutrophils
macrophages can phagocytize for more and larger material and are already in the tissue
how does a phagocyte recognize its “meal”
-phagocytes contain toll-like receptors (TLRs) that can recognize generic PAMPS and DAMPS
- rough surface
what should native substances have on their surface to repel phagocytes
protein coats
how is a cell marked for phagocytosis
a target will have an immunoglobulin/antibody attached to it
what part of the immune system secretes Interferons
innate immunity
what secretes INF and what does it do
-virally infected cell secretes it
- causes uninfected cells to produce enzymes that inhibit viral replication which prevents the spread of the virus to neighboring cells
what does the complement system consist of
30 distinct components that are in plasma in an inactive form and must be cleaved to become active
what is the complement system activated by
substances on the surface of microbes
what does the cascade of reactions in the complement system lead to
- enhancement of inflammation
-opsonization of pathogens - formation of a MAC that lyses pathogens
what immune system is the complement system activated by
both innate and acquired
what cell types require activation in acquired immunity
B and T lymphocytes
what type of immunity are B cells involved in
humoral
what type of immunity are T cells involved in
cell-mediated
what are helper T lymphocytes also called
CD4+
what are cytotoxic T lymphocytes also called
CD8+
what are antigens
molecules capable of inducing an acquired immune response by binding to B cell and T cell receptors and the production of antibodies against them
what type of molecule are antigens
surface peptides or polysaccharides
what is an epitope
molecular group on the antigen that is recognized by the immune system
what do antigen presenting cells do (APCs)
present antigens on their surface via MHC class II molecules
what do APCs bind to and activate
T helper cells -CD4
what do T helper cells (CD4) activate
humoral and cell-mediated immunity in acquired immunity
what are the antigen presenting cells and what do they do
- macrophages: ingest the pathogen and induce an inflammatory response if appropriate
-lymphocytes - dendritic cells: ingest the antigen and migrate to the nearest lymphoid organ
describe cell mediated immunity
activated T cells (NK cells, Cytotoxic T, CD8) result in killing of infected cells and stimulation of phagocytosis of bacteria and fungi
describe humoral immunity
activated B cells develop into plasma cells that secrete immunoglobulins. the antibodies neutralize toxins and viruses and enhance phagocytosis of bacteria
where do activated T and B cells initiate a response
in secondary lymphoid tissues
what do macrophages kill
bacteria
what do NK cells kill
virus infected cells and tumor cells
what do cytotoxic T cells kill
tumor cells and virus infected cells
what do T and B lymphocytes do upon activation
replicate a lot into clones and are secreted into the lymphatic circulation. then they cycle through the blood, tissue, and back to the lymph working as effector cells to eliminate the antigen
what causes Naive T cells to be made into T cell clones
cytokines
what are plasma cells
B cells that secrete antibodies
where are MHC class II cells found and what are they involved in
found on antigen presenting cells such as macrophages, dendritic cells and are involved in presenting antigens to T helper cells for cell mediated immunity
what do MHC class 1 do
code for markers that display unique characteristics of self and foreign antigens when the cell is infected
what does the interaction between MHC class II and T helper cell cause
activation of the T cell and creation of T cell clones
what does the interaction between MHC class I and cytotoxic T cell cause
destruction of an infected cell when it presents a foreign antigen
what are the actions of T lymphocytes
-growth and proliferation of cytotoxic and suppressor T lymphocytes
-growth and proliferation of B lymphocytes
-stimulates activation of more T helper cells
- activation of macrophage system
what does activation of the macrophage system cause
-attract and slow/stop macrophage migration away from inflamed regions
- stimulate more efficient phagocytosis
what cells have MHC Class I on their surface
all nucleated cells
what do cytotoxic T cells do after binding antigens
-secrete perforin molecules that punch holes in the membrane of the target which causes the cell to swell and lyse
- release of granzymes into the target through perforin channels that stimulate apoptosis
what do cytotoxic cells do after secreting substances
they can unbind and move to another cell
what do suppressor T cells do
-suppress functions of cytotoxic and helper T cells
-secrete inhibitory cytokines
- limit the immune systems ability to attack ones own tissues and add to immune tolerance
what are B cells activated by
intact antigens and activated T helper cells
what do B cells look like when activated
they enlarge and look like lymphoblasts
what can B cells differentiate into
plasmablasts which become plasma cells
where are immunoglobulins secreted
into the lymph and carried into the blood for circulation
what is the FAB region
the antigen binding region of the immunoglobulin
what does the Fc region of the immunoglobulin determine and what is it also called
-AKA constant portion
- determines diffusivity through membranes, complement attachment, and other biological properties
what does the heavy chain determine
Ig classification
what receptors do phagocytes contain and what does this cause
Fc receptors so antibody binding to an antigen leads to enhanced phagocytosis
what immunoglobulin is most abundant in the blood
IgG
what are the immunoglobulins
-IgG
- IgE
-IgA
-IgM
- IgD
what does IgG do
-complement activation
-opsonizes bacteria
-neutralizes bacterial toxins and viruses
-antibody dependent cell mediated cytotoxicity mediated by NK cells and macrophages
what is the primary antibody in the secondary response
IgG
what type of reactions is mediated by IgG
type 2 and type 3 hypersensitivity reactions
what type of reactions are mediated by IgE
type 1 hypersenstivity reactions
what does IgE do
defends against parasitic infections
what cells are activated by IgE
basophils, mast cells and eosinophils
where is IgA synthesized
by plasma cells in exocrine glands
what is the most abundant Ig in the body
IgA
what type of immunity does IgA mediate
mucosal immunity and neonatal immunity
what Ig is the most potent activator of complement
IgM
what is the largest Ig
IgM
what is the first Ig produced in response to an antigen
IgM
what is IgM secreted as
membrane bound as a monomer but can also be a pentamer
what do B cells begin to express on their surface when they reach maturity
IgM and IgD
where is IgD located and what does it do
-membrane bound, receptor on B lymphocytes surface
-aids in recognition by B lymphocytes
what happens to B cells after antigen activation and why
-they undergo antibody class switching to produce IgG, IgA, or IgE antibodies to allow daughter cells from the same activated B cell to produce different types of abs
describe the secondary immune response compared to the primary response
it is faster, stronger, and longer
what does binding of antigen binding site of an antibody with an antigen cause
-neutralization
-agglutination
-precipitation
what does exposed Fc portion following antigen binding by antibody cause
-complement fixation
- opsonization
-activation of NK cells
what immunoglobulins activate the complemetn system
IgM and IgG
what is tolerance
immunologic unresponsiveness to self antigens
where is tolerance seen
- clonal deletion occurs within the fetal thymus and bone marrow - central tolerance
- clonal anergy is when cells that are self antigenic become non functional -peripheral tolerance
what happens when self tolerance fails
autoimmune disease
what percentage of autoimmune diseases occur in women
90%
what are the theories for why immune tolerance fails
-failrue of regulation of self reactive lymphocytes
-exposure of T lymphocytes to antigens previously sequestered from the immune system
- molecular mimicry by invading pathogens
- modification of self antigens
-inappropriate expression of class II MHC molecules
where does molecular mimicry occur
in rheumatic fever where strep mutans resembles a portion of cardiac myosin
what are some autoimmune diseases we have learned about and what is targeted
- rheumatic fever
-myasthenia gravis- Ach disorder - lupus- targets red and white blood cells, platelets, etc
- Rheumatoid arthritis
- sjogrens syndrome
- multiple sclerosis - targets myelin sheath
- type 1 diabetes
-graves disease
what happens in the type 1 reaction
-IgE antibody is induced
-binds to mast cells and basophils
- the allergen cross links bound IgE and induces degranulation of mast cells and basophils
what happens in the type 2 reaction
antigens on a cell surface combine with antibody; this leads to complement mediate lysis
what happens in the type 3 reaction
antigen antibody immune complexes are deposited in tissues, complement is activated and polymorphonuclear cells are attracted to the site. they released lysosomal enzymes causing tissue damage
what happens in the type 4 reaction
helper T lymphocytes sensitized by an antigen release lymphokines upon second contact with the same antigen. the lymphokines induce inflammation and activate macrophages, which in turn release various mediators
where are mast cells and basophils most concentrated
in the lung, skin and GI tract
what does the release of secretory products from mast cell granules (histamine) do
increases vascular permeability, vasodilation, bronchial and visceral smooth muscle contraction, salivary and bronchial secretions and inflammation
what is the effect of a type 1 reaction do to respiratory resistance and BP
increases respiratory resistance and decreases BP
why can type 1 reactions be life threatening
bronchoconstriction and vasodilation causing hypotension and anaphalyxis
how long does a type 1 rxn take
within minutes
how long can IgE remain in the tissues
for years
what happens in type 1 hypersensitivity reactions if re exposed
the allergen contract the mast cells and stimulate degranulation and person can react immediately upon exposure
what is the late phase reaction in type 1 hypersensitivty reactions
-inflammatory infiltration of eosinophils, basophils, neutrophils and lymphocytes 2-4 hours after degranulation of mast cells and basophils
what are the treatment/preventative options for type 1 allergic responses
-avoid the allergen
-take drugs that block the action of lymphocytes, mast cells or chemical mediators
-undergo densitization therapy
what does desensitization therapy consist of
- controlled injections of the antigen
-works by producing IgG antibodies rather than IgE
what are IgG antibodies considered to be
blocking antibodies
if you are allergic what type of antibodies do you produce in response to environmental allergens
IgE
what type of things trigger IgE antibody production
-hay fever
-asthma
-drug insensitivity such as penicillin
-food allergies
- urticaria
-anaphylaxis
what are the most common food allergies
peanuts
-fish
-cow milk
-eggs
-shellfish
-soybeans
what are type 4 hypersensitivity reactions mediated y
T cells
what happens in a type 4 hypersensitivity reaction
-helper and cytotoxic T cells are activated and produce a cell mediated immune reaction which stimulates macrophage recruitment and inflammation
how long does it take for type 4 hypersensitivity reaction to kick in
delayed 1-2 days
where are type 4 hypersensitivity reactions restricted to
tissue area exposed to the pathogen
what is a common example of a type 4 hypersensitivity reaction
contact dermatitis
how do helper t cells and cytotoxic T cells respond upon repeat exposure in type 4 hypersensitivity reactions
increased response on repeated exposures
