Ch.15 adaptive immune system Flashcards
how is adaptive immunity developed?
by exposure to foreign antigens or by vaccination
is adaptive immunity broad or specific?
highly specific
what components does adaptive immunity include?
cells of mononuclear phagocyte system (macrophages and dendritic cells) and cytokines
why are memory cells important to adaptive immunity?
produce strong immune responses upon re-exposure to pathogens
vaccination relies on the abilities of which cells?
memory cells
what happens if a person only has adaptive immunity?
the adaptive immunity has no chance to be informed of infection, so microbes grow out of control
what happens if a person only has innate immunity?
the innate immunity initially helps control the microbial population, but without the intercession of the adaptive immune system, the population will eventually rise
cell-mediated immunity
response toward intracellular pathogens
intracellular pathogens
microbes that have breached the cell membrane and are already inside the cell
example of intracellular pathogen
viruses
humoral immunity
attack against extracellular pathogens
extracellular pathogens
microbes that are free in the tissues, organs, or bloodstream
steps of adaptive immunity
- dendritic cells find invaders and present them to naive helper T cells and naive cytotoxic T cells
- naive helper T cells and naive cytotoxic T cells become activated
- cytotoxic T cells differentiate into active cytotoxic T cells
- helper T cells deliver cytokines to activate macrophages to increase killing power and become more phagocytic, and activate naive B cells to begin the humoral immune response
- naive B cells differentiate into plasma cells which produce antibodies to bind to free-floating antigens (extracellular pathogens)
what are the 3 steps involved in adaptive immunity?
- activation of B and T cells
- proliferation and differentiation of B and T cells
- effector action (action that takes place to elimination infection) and consequence
adaptive immunity involves activity of what type of cell?
lymphocytes
what are the 2 main types of lymphocytes?
B lymphocytes (B cells) and T lymphocytes (T cells)
where do B cells mature?
bone marrow
Where do T cells mature?
thymus
what are the 2 types of adaptive immune responses?
- cell-mediated immune responses
- antibody immune responses
primary lymphoid organs
- bone marrow
- thymus
secondary lymphoid organs
- lymph nodes
- spleen
- tonsils
- MALT
- SALT
what does MALT stand for?
mucosa-associated lymphoid tissue
what does SALT stand for?
skin-associated lymphoid tissue
secondary lymphoid organs are the only place where what can occur?
where adaptive immune responses can be initiated
where do lymphocytes gather to contact antigens?
secondary lymphoid organs
where do hematopoietic stem cells reside and what do they give rise to?
bone marrow; all blood cells including lymphocytes
where are mature lymphocytes formed?
bone marrow
once B and T cells are mature, where do they gather to wait to encounter an antigen?
secondary lymphoid organs
peyer’s patches
tissues in intestinal wall that inspect samples on intestinal content
peyer’s patches are part of what secondary lymphoid organ?
MALT
MALT plays a crucial role in ____________, preventing _____________
mucosal immunity; preventing microbial invasion by mucous membranes
M cells
specialized intestinal epithelial cells that transfer material from intestinal lumen to peyer’s patches
antigens
molecules that the body recognizes as foreign and worthy of attack
how are antigens recognized?
by 3D epitopes on antigens
epitopes
certain regions of an antigen molecule that stimulate immune responses
what are the 2 classes on MHC proteins?
MHC class 1 and MHC class 2
MHC class 1
present on all cells except RBCs
MHC class 2
- present on antigen-presenting cells (APCs)
- include B cells, macrophages, and dendritic cells
what does MHC stand for?
major histocompatibility complex
cytotoxic T cells and helper T cells have numerous copies of what?
a surface molecule called T cell receptor
what is the relationship between MHC and antigen-presenting cells?
antigens bind in the antigen-binding groove of MHC molecules
cytotoxic T cells
destroy host cells that contain viruses
helper T cells
direct and assist various responses of humoral and cell-mediated immunity
T cell receptor
binds to specific antigens presented by dendritic cells or antigen-presenting cells
will T cell receptors bind to free floating antigens? why or why not?
no because it is a part of cell-mediated immunity, which is about attacking an intracellular pathogen)
are T cells part of cell-mediated or humoral immunity?
cell-mediated
T cell activation steps
- recognition of presented antigen
- stimulatory signals secreted from APC
APC
antigen-presenting cell
how are cytotoxic T cells and helper T cells different physically?
they have different CD markers
once infected, what do cytotoxic T lymphocytes do in cell-mediated immunity?
- tells infected “self” cells to go through apoptosis
- some cells with become memory CTLs and remain in secondary lymphoid organs in case the antigen presents again
once infected, what do T helper cells do in cell-mediated immunity?
- produce cytokines that activate B cells and macrophages
- some cells become memory T helper cells that will remember those specific antigens
T regulator cells
suppress immune activation from overreacting and responding to harmless substances
function of B cells in humoral immunity
have numerous copies of a B cell receptor on their cytoplasmic membrane and are activated and divide upon antigen recognition
B cells include:
plasma cells and memory cells
plasma cells
activated B cells that produce antibodies
B cell receptor
membrane-bound version of antibody (free floating antigen) that the B cell is genetically programmed to make
what happens when a naive B cell encounters an antigen that its B cell receptor can combine with?
an interaction signals the B cell to respond
what must occur for a B cell to be activated?
- B cell encounters an antigen that its B cell receptor can bind to
- T helper cell gives a 2nd signal that the antigen should be eliminated
what occurs once a B cell is activated?
the B cell proliferates and differentiates into plasma cells (which produce antibodies) and memory cells (which respond quickly upon re-exposure of the same antigen)
steps for clonal selection and expansion of lymphocytes
- immature lymphocytes in bone marrow
- naive lymphocytes form when immature lymphocytes matures and is moved to secondary lymphoid organ
- activated lymphocytes occurs when the cell comes into contact with the epitope it is programmed to respond to
- effector lymphocytes/memory lymphocytes
at what point are lymphocytes programmed to recognize specific epitopes on specific antigens?
when they are moved to secondary lymphoid organ
activation of lymphocytes involves what?
coming into contact with an antigen and being signaled by a helper T cell
what process are effector lymphocytes and memory lymphocytes formed from?
clonal selection and expansion
what do effector lymphocytes do?
produce antibodies
what do memory lymphocytes do?
stay in the body and produce a quick, strong response to the second exposure of the same antigen
what causes clonal selection and expansion in B and T cells?
when an antigen and antibody are bound
clonal selection occurs in ___________ (primary/secondary) response to antigen
primary
which types of cells does clonal selection apply to?
both T and B cells
one antigen has ___ (#) B and T cell(s)
1
antibodies produced by plasma cells upon first exposure are what shape?
pentamer
which immunoglobulin is the first produced in primary response?
IgM
what occurs once IgM antibodies are produced in primary response? what is this process called?
T4 cells can send cytokines to induce some of the activated B cells to switch their genetic program and differentiate into plasma cells which can secrete other classes of antibodies (IgG or IgA); class-switching
class-switching
once IgM antibodies are produced in primary response, T4 cells can send cytokines to induce some of the activated B cells to switch their genetic program and differentiate into plasma cells which can secrete other classes of antibodies (IgG and IgA)
what antibody is normally produced in the lymph node?
IgG
what occurs in secondary response to an antigen?
the antigen is detected by memory cells, which quickly differentiate to form plasma cells which rapidly produce antibodies
what antibodies are produced in secondary response and where?
IgG in lymph nodes
IgA in MALT
steps of clonal expansion by a B cell
- B cell receptor binds to antigen
- B cell internalizes antigen through endocytosis
- B cell degrades antigen into peptide fragments
- peptide fragments are presented on MHC class II molecules
5a. if a microbial antigen is presented, the T helper cell recognizes the antigen fragment and delivers cytokines to a activate B cell
5b. if a harmless antigen is presented, the T helper cell does not recognize the antigen fragment and the B cell becomes anergic
antibodies
Y-shaped proteins
what is the purpose of having T helper cells?
acts as a safety mechanism to ensure the body responds to antigens in an appropriate way
what are the 2 general parts of antibodies?
arms and stem
enzymatic digestion of antibodies yield ______ types of fragments
2
what are the fragments that are yielded by enzymatic digestion of antibodies?
- Fab (antigen-binding fragment): binds antigen
- Fc: crystallized fragment
what are antibodies made up of?
2 identical heavy chains and 2 light chains
what are the regions of an antibody?
variable region and constant region
variable region of antibody
includes area where antigens bind with antibody molecules and contains antigen binding site; has high level of variability (different for every type of antibody)
constant region of antibody
includes Fc region and part of the 2 Fab regions; very consistent and can be recognized by many different components and interact with proteins of the complement system
what is Fc region recognized by?
Fc receptors on macrophages
where on the antigen do antibodies bind to?
epitopes/antigenic determinants
what are the 6 possible protective outcomes that antibodies may accomplish when they bind to a specific antigen?
- neutralization
- opsonization
- complement system activation
- immobilization and prevention of adherence
- cross-linking
- antibody-dependent cellular cytotoxicity (ADCC)
neutralization
antibodies bind to specific viruses and toxins; once coated with antibodies, these viruses and toxins can no longer attach to host cell
opsonization
antibodies attach so that phagocytic cells recognize antigen, making phagocytosis easier
complement system activation
multiple molecules of an antibody binds to antigen and causes complement proteins to attach to side-by-side Fc receptors of the antibody, activating the complement cascade and leading to opsonization by C3b, inflammatory response, and lysis and foreign cells
immobilization and prevention of adherence
antibodies bind to flagellum or pilli to prevent movement and adherence
cross-linking
ends of 2 arms of an antibody molecule can bind to separate but identical antigens; several antibodies work together to bind antigens on bacteria in this way, causing clumping and making it a target for phagocytosis
antibody-dependent cellular cytotoxicity
IgG binds to virally-infected cell or tumor cell and the antibody serves as a marker for natural killer cells, which attach and kill the marked cell
what do natural killer cells release when activated?
cytokines
what cells do natural killer cells kill?
- cells that lack MHC I (virus infected and certain tumor cells)
- have Fc for IgG and kill cells coated with IgG (antibody-dependent cellular cytotoxicity)
what are the 5 antibody classes?
IgG
IgA
IgM
IgE
IgD
what is the first antibody class produced during a primary response to an antigen?
IgM
which antibody class is the principal class produced in response to some T-independent antigens?
IgM
T-independent antigens
antigens that don’t require B cells to receive a signal from a T helper cell to become activated and mount a response
IgM makes up what percentage of circulating antibodies?
5-13%
example of T-independent antigen
lipopolysaccharide
what structure is IgM?
pentamer
pentamer structure
5 monomeric subunits giving 10 antigen-binding sites
why is the pentamer structure of the IgM antibody appropriate for cross-linking?
it aggregates very effectively
IgM’s large size prevents ___________
crossing from the bloodstream to tissues
which antibody plays the primary role in bloodstream infections and why?
IgM because it cannot cross from the bloodstream to the tissues
IgM is the most effective antibody class for __________
triggering the classical pathway of complement system
IgG makes up what percentage of serum immunoglobulins?
80-85%
what is the most commonly found immunoglobulin in serum?
IgG
T/F: IgG exits bloodstream to enter tissues
True
which antibody provides the longest-term protection?
IgG
what is the longest living antibody?
IgG
which antibody is the first and most abundant circulating class produced during secondary response?
IgG
IgG antibodies protect through what mechanisms?
- neutralization
- aggregation
- opsonization
- complement
- activation
antibody-dependent cellular cytotoxicity
which antibody is transported across placenta to fetus’s bloodstream?
IgG
which antibodies are babies born with?
IgG and IgM
secretory IgA
dimer IgA
what is IgA important for?
mucosal immunity
where does IgA mostly form?
mucous membranes
what areas of the body needs mucosal immunity?
- GI, genitourinary, and respiratory tracts
- secretions including saliva, tears, and breast milk
IgA protects breast-fed infants against what?
intestinal pathogens
what mechanisms are used by IgA to protect?
- neutralizing toxins and viruses
- interfering with attachment of microbes to host cells
what produces IgA?
plasma cells of mucosa-associated lymphoid tissue
secretory component of IgA
attaches antibody to mucous
what is the most abundant immunoglobulin class produced?
IgA
IgD
involved with development an maturation of antibody response
what percentage of IgD makes up all serum immunoglobulins?
1%
what is IgE bound to?
membranes of basophils and mast cells which use IgE to detect antigens
what happens when IgE is activated by an antigen binding to 2 adjacent IgE molecules carried by mast cells?
cell releases histamine and other inflammatory mediators
what is IgE important for eliminating?
parasitic worms
basophils and mast cells release chemicals when IgE binds to _________
- normally harmless foods
- dust
- pollen
what is the body’s response to IgE binding to things?
chemicals are released, causing coughing, sneezing, and swelling
function of IgD
serves as an antigen receptor for initiating the differentiation of B cells
what is IgE bound to?
basophils and mast cells
functions of IgE
- inflammation
- allergic responses
- combating parasitic infections
which is the first antibody produced in primary response to an antigen?
IgM
which is the largest immunoglobulin?
IgM
what does IgM present in newborns indicate?
an in-utero or newborn infection
which is the first immunoglobulin made by a newborn?
IgM
which immunoglobulin is the first circulating immunoglobulin to appear in response to an antigen?
IgM
function of IgA
prevents attachment of viruses and bacteria to epithelial cells
which immunoglobulin acts as the primary defense against local infections in mucosal tissue?
IgA
where is IgA found?
- saliva
- tears
- breast milk
- bronchial, gastrointestinal, prostatic, and vaginal secretions
functions of IgG
- protects against bacteria, toxins, and viruses in body fluids
- activates complement system
which immunoglobulin crosses the placenta and transfers immunity from mother to fetus?
IgG
where is IgG present?
body fluids
which is the most abundant immunoglobulin?
IgG
what are the 3 lines of defense of the immune system?
- skin, mucous membranes, enzymes, natural flora on the skin and in the GI tract
- innate immunity: phagocytes, natural killer T cells, granulocytes, complement proteins, macrophages
- acquired immunity: antibodies, B and T lymphocytes
What is the endogenous process?
What is the exogenous process?
