Adaptive Immunity Part 1 Flashcards
Adaptive immunity is considered nonspecific/specific (Choose one).
Specific!
Adaptive (acquired, specific immunity) makes up the ___ line of defense. What cells are involved in this line of defense?
Third; Specialized lymphocytes (T & B cells) & plasma cells (antibody factories)
What are the 2 types of adaptive immunity, their primary cells, and their location of action?
- Antibody-mediated (aka humoral) adaptive immunity - B cells, plasma cells, and circulating antibodies; directed against extracellular pathogens
- Cell-mediated adaptive immunity - T cells; directed against extracellular pathogens, cancer cells, & transplanted tissue
T/F Both arms of adaptive system, antibody and cell mediated, produce memory cells.
T
Helper T-cells may trigger activation of which cells?
Both T and B cells
Given that human cells contain only about 35,000 genes, how could a billion (10^9) or more different antigen receptors (epitopes) possibly be generated?
a process called genetic recombination = diversity of antigen receptors in both B cells and T cells is the result of shuffling and rearranging a few hundred versions of several small gene segments
- these gene segments are put together in different combinations as the lymphocytes are developing in bone marrow and thymus
T/F Before a particular antigen ever enters the body, T cells and B cells that can recognize and respond to that intruder are ready and waiting.
T
An amazing feature of the human immune system is its ability to recognize and bind to at least _____ different epitopes.
a billion (10^9)
____ = antigen receptors in B cells and T cells
epitopes
What are the 2 phases of the adaptive immune response?
- Generation of Clonal Diversity
- Clonal Selection
What is produced from the Generation of Clonal Diversity?
Production of immunocompetent, naïve T and B cells with all possible receptors for antigen (diverse receptors for 10^9 antigens)
Where does generation of clonal diversity take place?
Takes place in the primary/central lymphoid organs:
- Thymus for T cells
- Bone marrow for B cells
During maturation in generation of clonal diversity, B cells gain _____, and T cells gain _____. This results in: ______
- antigen receptor molecules (BCRs = B-cell receptors)
- receptors called T-cell receptors
- immunocompetent but naïve T and B cells
Where do immunocompetent T and B cells go after maturation in the primary lymphoid organs?
T and B cells migrate to secondary lymphoid organs (spleen and lymph nodes) to wait for antigens
When does generation of clonal diversity occur?
During fetal life
T/F No foreign antigen is involved in generation of clonal diversity.
T
What is meant by “immunocompetent but naïve” cells?
Cell is ready to meet antigen but has not met it yet
When does clonal selection occur?
At birth and proceeds throughout life
What are the 3 processes of clonal selection?
- Selection,
- Proliferation,
- & Differentiation of…
…individual T and B cells with receptors for a specific antigen
What initiates the clonal selection process?
T and B cells (in the secondary lymphoid organs) are ‘presented’ an antigen
Where are the B and T cells as they wait to be presented with an antigen during the clonal selection process?
In the secondary lymphoid organs (spleen and lymph nodes)
What are the results of clonal selection?
- Expansion of the population (cloning)
- Differentiation into antibody-secreting plasma cells or mature T cells or both
What are the final products of clonal selection?
Plasma cells that produce antibodies
Effector T cells (helper T cells, cytotoxic T cells, regulatory T cells)
Memory B and T cells
Where does B-cell maturation occur? Which process of adaptive immunity is B-cell maturation a part of?
- Bone marrow
- Generation of clonal diversity
To which secondary lymphoid tissue do mature, immunocompetent B cells migrate to after generation of clonal diversity?
lymph nodes
Which surface antibodies are expressed on mature B cells?
surface IgM (macro-globulin) and IgD
Changes during B-cell maturation include:
1. ___
2. ___
3. ___
- development of BCRs (antigen receptor molecules)
- expression of surface antibodies (IgM and IgD) & other surface proteins (CD21 - a complement receptor)
- Negative feedback via clonal deletion
Surface markers on mature B cells include:
- CD21 - a complement receptor
- Antibody anchored to PM (IgM & IgD)
All of the surface antibodies on an individual B cell are ____ for the same antigen
Specific!
A(n) ____ initiates clonal selection.
antigen
The ____ cell membrane has a more complex array of proteins than _____ cells.
T; B
What does the T-cell membrane consist of and what are the functions of its components?
Consists of:
- Antibody-like transmembrane protein (TCR = T-cell receptor) - responsible for recognition and binding to specific antigen by serving as an antigen receptor on surface of T cells
- Accessory proteins for intracellular signaling
Antigen receptors on the surface of T cells, called T-cell receptors (TCRs), recognize and bind to ____ foreign antigen fragments that are presented in _______ complexes from the ____.
- specific
- antigen-MHC Class II
- Antigen Presenting Cell (APC)
T/F TCR serve as antibodies.
F - BCRs are antibodies; TCRs have similar functions but are NOT antibodies
Which cell capture antigens from within the body and present them on MHC proteins to naïve T cells?
APCs (Antigen presenting cells)
MHC Class II molecules on APCs will carry a specific antigen to _____ T cell
CD4+
_________ on APCs will carry a specific antigen to CD4+ T cell
MHC Class II molecule
Known as “self antigens” located in the plasma membrane of body cells
Major Histocompatibility Complex (MHC) proteins/Human Leukocyte Antigens (HLAs) (because they were first identified on leukocytes)
What is the normal function of MHC complexes?
to help immune cells recognize that an antigen is foreign, not self
T/F Your MHC proteins are unique, unless you have a twin
T
MHC-I molecules/glycoproteins are built into the plasma membrane of ____
- all body/human cells that have a nucleus (this excludes erythrocytes)
______ are built into the plasma membrane of all body/human cells without a nucleus
MHC-I molecules
MHC-II molecules appear on the surface of _____
APCs (I.e. Dendritic cells)
_____ molecules appear on the surface of APCs
MHC-II
Molecule that presents endogenous antigens derived from intracellular proteins
MHC-I
MHC-I presents _____ antigens derived from _____
- endogenous
- intracellular proteins
MHC-I antigen receptor complex interacts with ____ and T-cell receptors on ____ T cells.
CD8; cytotoxic
____ antigen receptor complex interacts with CD8 and T cell receptors on cytotoxic T cells
MHC-I
What message is sent by MHC-I molecules of healthy cells?
they display normal self-antigens (“This cell and cells like me are ‘self’ - leave us alone!)
What message is sent by MHC-I molecules of unhealthy (cancerour or virus infected) cells?
they display ‘nonself’ antigens = proteins synthesized internally in the unhealthy cells
(“Alien present inside; kill me”)
MHC-II presents ___ antigens derived from ______
exogenous; extracellular organisms
____ presents exogenous antigens derived from extracellular organisms via _____
MHC-II; phagocytosis - how antigen fragments are taken up and degraded
MHC-II antigen receptor complex interacts with ___ and T-cell receptors on ___ T cells
CD4; helper
______ antigen receptor complex interacts with CD4 and T-cell receptors on helper T cells
MHC-II
What message is sent by macrophages and dendritic cells when they display captured external nonself antigens? Which MHC complex does this involve?
“Invader looks like this; go find more enemies like this and kill”
MHC-II is present on the surface of _____ & ______
Macrophages; dendritic cells
What must happen for an immune response to occur?
B cells and T cells must recognize that a foreign antigen is present
What occurs during antigen processing?
antigenic proteins (exogenous (MHC-II) and endogenous (MHC-I) antigens) are broken down into peptide fragments that then associate with MHC molecules
MHC class I and II molecules are assembled in the ER of the APC or infected cells to prepare for presentation to the B and T cells
Where are the MHC complexes assembled in the cell?
endoplasmic reticulum of APCs or infected cells
What is antigen presentation?
the insertion of the antigen-MHC complex into the plasma membrane of a body cell
What are the 2 ways in which antigen processing and presentation can occur?
- Exogenous antigens (MHC-II, CD4, APCs, Helper T cells)
- Endogenous antigens (MHC-I, CD8, body cells with nucleus, cytotoxic T cells)
What are the 3 “professional” APCs?
- Dendritic Cells - process antigen from a site of inflammation to T-cell/B-cell rich areas of lymph nodes
- Macrophages
- B lymphocytes - present antigen to T helper cells that facilitate humoral immune response; subset of B-cells become professional APCs
B lymphocytes - APCs which present antigen to ____ T cells that facilitate ____ immune response.
helper; humoral
___ lymphocytes - APCs which present antigen to helper T cells that facilitate humoral immune response
B
Dendritic cells - APCs which process antigen from site of _____ to _____-rich areas of lymph nodes
inflammation; T-cell/B-cell
______ - APCs which process antigen from site of inflammation to B-cell/T-cell-rich areas of ____
Dendritic cells; lymph nodes
Intruders such as bacteria and bacterial toxins, parasitic worms, inhaled pollen and dust, and viruses that have NOT yet infected a body cell are examples of _____.
exogenous antigens
Where are APCs located?
They are strategically located in places where antigens are likely to penetrate the innate defenses and enter the body, such as the skin and linings of the respiratory, gastrointestinal, urinary, and reproductive tracts (mucous membranes)
After processing and presenting an antigen, APCs migrate from tissues via _____ to _____
lymphatic vessels; lymph nodes
What informs immune system cells that intruders are present in the body and that we should begin activating the adaptive immune response?
presentation of an antigen together with MHC-1 or MHC-II
List the mechanism of processing EXOGENOUS antigens.
- Ingestion of the antigen
- Digestion of antigen into peptide fragments
- Synthesis of MHC-II molecules
- Packaging of MHC-II molecules
- Fusion of vesicles
- Binding of peptide fragments to MHC-II molecules
- Insertion of antigen-MHC-II complexes into the PM
Viral proteins produced after a virus infects the cell and takes over the cell’s metabolic machinery, toxins produced from intracellular bacteria, and abnormal proteins synthesized by a cancerous cell are examples of ________ antigens
Endogenous
Fragments of endogenous antigens are processed and then presented with ____ proteins on the surface of _____ cells
MHC-I; infected body cells
Fragments of ____ antigens are processed and then presented with MHC-I proteins on the surface of infected body cells.
endogenous
T/F Most cells of the body can process and present endogenous antigens
T - endogenous antigens are processed in all body cells with a nucleus; exogenous antigens are just processed within APCs
What does the display of an endogenous antigen bound to an MHC-I molecule signal?
That a cell has been infected and needs help
The display of a(n) _____ antigen bound to a ____ molecule signals that a cell has been infected and needs help.
endogenous; MHC-I
List the steps to the mechanism for processing ENDOGENOUS antigens.
- Digestion of endogenous antigen into peptide fragments
- Synthesis of MHC-I molecules
- Binding of antigen-peptide fragments to MHC-I molecules
- Packaging of antigen-MHC-I complexes
- Insertion of antigen-MHC-I complexes into the PM
_____ = the process by which a lymphocyte proliferates and differentiates in response to a specific antigen.
Clonal selection
What is produced from clonal selection?
the formation of a population of identical cells (CLONES) that can recognize the SAME SPECIFIC antigen as the original lymphocyte
- each cell within the clone has the same type of antigen receptor as the original lymphocyte
- once clonal selection occurs, there are thousands of lymphocytes that can respond to that antigen
What are clones and their function?
Clones are a population of identical cells formed by clonal selection in which each cell within the clone has the same type of antigen receptor as the original lymphocyte
- therefore, they can recognize the same specific antigen as the original lymphocyte
A lymphocyte that undergoes clonal selection (activation) gives rise to what 2 major types of clonal cells?
- Effector cells - active helper T-cells, active cytotoxic T-cells, and plasma cells (B-cell clone)
- Memory cells - memory helper T cells, memory cytotoxic T cells, memory B cells
Which type of clonal cells will eventually die after the immune response has been completed?
effector cells
Which type of clonal cells do not die at the end of an immune response?
memory cells
