Class 6 - Adaptive Immunity Flashcards
adaptive immunity is the body’s ability to…
defend itself against specific invading agents called antigens (Ags)
what are two main properties of adaptive immunity?
- specificity (distinguishing self from NON-self)
2. immunological memory
what is self in terms of adaptive immunity?
the body’s own constituents
what is considered ‘non-self’ in terms of adaptive immunity?
foreign cells and tissues (altered self)
adaptive immunity involves what 2 main types of lymphocytes…
T lymphocytes (inside)
B lymphocytes (outside)
both B&T cells originate in the _____ and the _____ of the embryo
bone marrow
thymus gland
Where do B cells complete their maturation?
bone marrow - continues throughout life
Where do T cells develop from?
the pre-T cells that migrate from the bone marrow to the Thymus, where they mature
most T cells arise before puberty, but…
the continue to mature and leave the thymus throughout life
define ‘immunocompetence’
capability for the immune response
where do T cells develop their immunocompetence?
the thymus gland
where do B cells develop their immunocompetence?
bone marrow
The two major types of T cells that exit the thymus gland to search for antigens are…
- Helper T cells (CD4 T cells)
2. Cytotoxic T cells (CD8 T cells)
In the bone marrow, the B cells ____ or ____ to the ____ tissues, but they won’t exit their location to search for the antigens.
stay
migrate
lymphatic
What are two types of adaptive immunity?
- cell-mediated immunity (cells attacking cells- cytotoxic T cells attack invading antigens)
- antibody-mediated immunity (humoral immunity- B cells differentiate into plasma cells)
B cells differentiate into _______ which secrete _____
plasma cells which secrete antibodies (Abs)
Both T and B cells work together to…
eliminate the antigens from the body
Helper t cells aid in what 2 reponses?
cell-mediated and anti-body mediated immunity
What is the name of the process that the body uses to respond to being outnumbered by attacking antigens?
clonal selection
What does clonal selection do when the body is being attacked by anitgens?
on each cellular encounter, the cells clone themselves, which increases the amount of specific cells able to respond to that specific antigen.
Where does clonal selection occur?
Secondary lymphatic organs and tissues - lymph nodes, spleen, lymphatic nodules
Name the 2 major clone cells
effector cells and memory cells
what do effector cells do?
carry out the responses to destroy the antigens
name 3 kinds of effector cells
active helper T cells
active cytotoxic T cells
plasma cells
memory cells do not participate actively in the initial immune response, but instead they participate in…..
actively in a second response to the antigen
what do memory cells proliferate into?
more effector and memory cells
most memory cells do not die at the end of the immune response, including what 3 types of cells?
memory helper T cells, memory cytotoxic T cells, memory B cells
usually, the trigger for the immune response are only some small part of the antigen called____
epitopes
What is an antigens overall role when it comes to immune responses?
they provoke an immune response (immunogenicity) and react specifically with the antibodies/cells they provoked (reactivity)
Most antigens have several epitopes which can induce the production of….
different antibodies (paratopes) or activating different T cells against them
most often, antigens are large complex proteins, however there are also ‘haptens’ which are small substances that can only be antigenic when….
attached to larger molecules
‘hapten-stimulated responses’ cause what kind of reactions?
allergic rxns to drugs, ex. penicillin
what do major histocompatibility complex (MCH) antigens help T cells do?
help T cells recognize foreign antigens (non-self)
how do B cells respond when they recognize ‘non-self’ antigens?
b cells bind to antigens in the lymph, interstitial fluid and plasma
how do T cells respond when they recognize ‘non-self’ antigens?
t cells can only recognize epitopes of antigenic proteins (processed and presented in a certain way by other cells in the body)
bacteria, toxins, parasites, viruses and pollen are all examples of what?
exogenous antigens - foreign antigens outside the cell
what are exogenous antigens ingested, processed and presented to the t-cell by?
antigen-presenting cells (APCs)
antigen-presenting cells ingest and process foreign antigens with what?
different MHC molecules
where do antigen presenting cells do their antigen presentation?
on their plasma membrane for T cell recognition
during an adaptive immune response, where and what do t cells do when they recognize the antigen?
APCs migrate to the lymphatic tissue to present the antigen to the t cell
t cells recognize the antigen, bind to epitopes of it and trigger the adaptive immune response
what 2 things secrete cytokines (small peptide hormones)?
- lymphoctyes
2. antigen-presenting cells
what are 3 major roles of cytokines?
- STIMULATE proliferation of progenitor cells in bone marrow
- INHIBIT normal cell growth and differentiation function
- REGULATE innate defences or adaptive immunity responses
about what fraction of lymphocytes are T cells?
2/3 (most are inactive)
what two events need to happen, at the same time, in order for a T cell to be activated
- bind to foreign antigen
2. receive a second signal = ‘co-stimulation’
What two components need to interact for the generation of the activated helper t cell?
- inactive helper t cell
2. the antigen presenting cells with the specific antigen
activated helper t cells clone and start secreting a variety of ____ to activate other _____
cytokines
T&B cells
define ‘co-stimulation’
the activation and clonal selection of helper t cells (CD4 T cells)
cytotoxic t cells are also called…
CD 8 T cells
Cytotoxic T cells can be effective against, what 3 things?
- cells infected with microbes
- some tumour cells
- cells of tissue transplant
name 3 cytotoxic t-cells
granzymes, granulysin, perforin
name the immune response capable of destroying tumor antigens?
immunological surveillance
immunological surveillance is carried out by what 3 cells?
cytotoxic T cells, NK cells, macrophages
cell-mediated immunity involves what cells?
t cells
anti-body mediated immunity involves what cells?
b cells - stay in lymphatic tissues
what happens when a b cell encounters a specific antigen and the b cell becomes activated and clones….
clonal selection makes the plasma cells aka effector cells and the memory cells
what do plasma (effector) cells secrete after exposure to an antigen/co-stimulation of the helper T cell and for how long?
antibodies, a few days after exposure
what do antibodies bind to, and what do they form?
specific antigens to form antigen-antibody complexes
antibodies are also known as?
immunoglobulins
what are the 5 classes of antibodies?
IgG (80%) IgA (10-15%) IgM (5-10%) IgD (.2%) IgE (.1%)
where are IgG present?
cross the placenta before birth
where are IgA present?
breast milk, sweat, tears
where are IgM present?
secreted after first exposure
where are IgD present?
involved in B cell activation
where are IgE present?
allergic reactions
What are 5 actions antibodies carry out by forming antigen-antibody complexes?
- neutralize antigen
- immobilize bacteria
- enhance phagocytosis
- agglutinating and precipitating antigens
- active complement system
where are the proteins of the complement system produced?
liver
where are proteins of the complement system found?
plasma and within tissues all over body
what 3 methods do the proteins of the complement system cause that destroys microbes?
phagocytosis (opsonization),
cytolysis,
inflammation
Immunological memory is due to what two things?
presence of long-lasting antibodies and very long-lived lymphocytes (immune response becomes much quicker in subsequent exposures)
What 3 events occur less optimally in a primary immune response after first exposure?
no antibodies for several days
slow rise of antibodies - IgM first, then IgG
gradual decline of Ab’s
what cell may remain for decades and proliferate very quickly after encountering a specific antigen?
memory B cells
how does naturally acquired active immunity occur?
direct exposure to the pathogen, development of a disease, recovery then acquire immunity
how does artificially acquired active immunity occur?
receive a vaccine
how does naturally acquired passive immunity occur?
IgG pass from mom to fetus via placenta
how does artificially acquired passive immunity occur?
IV of antibodies
what 2 traits must a t cell to function?
- self recognition
2. self-tolerance
self-recognition of a t cell….
recognizing own MHC proteins
self- tolerance of a t cell…
lack of reactivity to own proteins
what does loss of self-tolerance lead to?
autoimmune disease
the development of self-recognition in t cells occurs where?
thymus gland of fetus
what happens during positive selection process first with t cells during development of self-recognition?
only t cells capable of recognizing the self (MHC proteins) survive
what happens during negative selection process second with t cells during development of self-recognition?
t cells that do not react to self (MHC proteins) survive (reactive ones=inactived/anergy or die/apoptosis)
during the development of self-tolerance in T cells, they emerge from the thymus and migrate to the lymphatic tissue of an adult where the….
mature T cells are able to recognize antigen with co-stimulation proliferation –> T cells able to recognized antigen WITHOUT co-stimulation are inactivated (anergy) or die (deletion)
development of self-recognition and self-tolerance for B cells occur where?
both occur in BONE marrow
What b cells survive the development of self-recognition/tolerance?
b cells that DO NOT recognize self (MHC proteins)
What happens to b cells that are released into the plasma after the bone marrow?
b cells the recognize antigen with co-stimulation PROLIFERATE AND DIFFERENTIATE into plasma cells (those without co-stimulation are inactivated)
what is required for survival of T cells during NEGATIVE selection?
t cells must be able to recognize self- MHC proteins but NOT self- peptides
what is required for survival of B cells during NEGATIVE selection?
mature b cells recognizes antigen at first signal and then co stimulation occurs as a second signal and b cells are activated so they proliferate and differentiate into clone of plasma cells
what happens to b cells if there is no co stimulation after the negative selection process?
there is inactivation of the B cells in secondary lymphatic tissues and blood!
T cells undergo positive selection to ensure…
self-MCH protein recognition
t cells undergo NEGATIVE selection to ensure…
they do not react to self-proteins
negative selection involves what 2 processes?
deletion and/or anergy
b cells undergo negative selection to ensure…
they do not react to self-proteins
b cells develop tolerance through…
deletion and anergy
what is autoimmunity….
immune system failing to display SELF-TOLERANCE (females 2x more likely)
self-tolerance breaks down under the influence of unknown environmental triggers or certain genes, which leads to..
the reactivation of SELF-REACTIVE CLONES of B and T cells
define ‘autoantibodies’
antibodies that bind to and stim OR block self-antigens (older individuals will produce more autoantibodies)
