5.4: The Adaptive Immune System Flashcards
(27 cards)
1
Q
what are the 2 cell types of the adaptive immune system?
A
- B lymphocytes (B cells)
- T lymphocytes (T cells)
2
Q
what are the two types of T cells
A
- T-Cytotoxic cells (Tc cells)
- T-Helper cells (Th cells)
cytotoxic = cell killing
3
Q
B lymphocytes (B cells)
A
- Antibody producing cells
- Involved in the humoral immune response
4
Q
T-Cytotoxic cells (Tc cells)
A
- destroy abnormal body cells (ex. cells infected by viruses)
- involved in cell mediated immune response
5
Q
T-Helper cells (Th cells)
A
- Help B and Tc cells prepare for an immune response
- involved in humoral and cell mediated response
(like sargent tell B and Tc cells what to do)
6
Q
what are the 3 types of antigen presenting cells?
A
- Macrophages
- dendritic cells
- B cells
7
Q
What do antigen presenting cells do?
A
- Engulf foreign material
- Break it apart (regardless of what it is)
- Present its antigens on the surface to other cells of the immune system (T cells)
- antigens must be presented along with the major histocompatibility complex (MHC):
-set of self-antigens (antigens produced by your own cells)
-MHC classes I and II
8
Q
which cells have MHC (major histocompatibility complex) class 1
A
- found on all nucleated body cells (not only professional antigen presenting cells)
9
Q
how does MHC 1 work?
A
- identifies the cell as “self”
- can present endogenous antigen to Tc cells
-any antigen made inside the cell - does this bc if a Tc cell recognizes the antigen as foreign, it will be activated to destroy cells that display that antigen (bc they could be antigens from virus inside cell that was infected, so presents our cells to show our Tc cells that they belong)
10
Q
which cells have MHC (major histocompatibility complex) class 2
A
- found only on professional antigen presenting cells:
-Dendritic cells, macrophages and B cells
11
Q
How does the MHC (major histocompatibility complex) class II work?
A
- present exogenous antigens to Th cells
-antigens that were taken up by phagocytosis - If a Th cell recognizes the antigen as foreign, it will be activated to “help” other components of immunity prepare a immune response
12
Q
how do T-helper (aka Th or CD4+ cells) work?
A
- Each Th cell has T-cell receptors (TCR) for one specific antigen
- Antigen must be presented by an APC (antigen presenting cell), along with MHC class II
-only the correct antigen can activate the Th cell
13
Q
what are other names for T-Helper cells
A
- Th cells
- CD4+ cells
ex: virus HIV only attaches to CD4 receptor only affecting cells with this receptor
14
Q
What are the 4 subsets Th cells differentiate into? and what do each do?
A
- Th1 cells secrete cytokines to activate macrophages and Tc cells
- Th2 cells secrete cytokines to activate B cells
- Th17 cells secrete cytokines to recruit neutrophils
- Memory Th cells -long lived cells that can respond quickly if the antigen is ever encountered again
overall Th cells basically regulate everything
15
Q
describe how the humoral (antibody mediated) response begins
A
- Begins when a B cell encounters a foreign antigen
- Each B cell has receptors for one specific antigen (B cell receptor, usually a molecule of surface IgD -B cell antibody)
- Binding of that antigen to the receptor causes the B cell to ingest and break down the intruder
- presents the antigen to a Th2 cell along with MHC class 2
16
Q
describe what happens after the antigen is presented to a Th2 cell with MHC II in the humoral (antibody mediated) response
A
- If the antigen fits into the Th2 cell’s TCR, the Th2 will secrete cytokines to activate the B cell
- B cell undergoes clonal selection and expansion. It multiplies and differentiaties into:
- Mostly Plasma cells and some Memory B cells
17
Q
Describe the Plasma cells
A
- Type of B cells produced in the clonal selection and expansion part of the humoral (antibody mediated) response
- Short lived B cells that secrete large amount of antibody
- travel through blood and tissue to deal with the pathogen
18
Q
Describe the Memory B cells
A
- Type of B cells produced in the clonal selection and expansion part of the humoral (antibody mediated) response
- Long lived cells that maintain memory of the pathogen
- If they encounter the pathogen again, they can respond rapidly by producing a new generation of plasma cells
19
Q
what are the steps of activation of B cells and humoral response?
A
- B cell encounters an antigen and engulfs it
- B cell presents fragments of the antigen to Th2 cell using MHC class II
- The B cell undergoes clonal selection and expansion
- Plasma cells produce antibodies to help fight the infection, and memory cells maintain long term memory in case the intruder is ever encountered again
20
Q
describe the primary response in antibody production
A
- lag time of days to weeks (bc it takes time for b cell to find specific intruder)
- B cells need time to be activated
- The first antibody produced is IgM, followed by IgG
- Major outcome is the production of memory B cells (happens too slowly to overcome sickness, just helps you in the future)
21
Q
Describe the secondary response in antibody production
A
- no lag period
- memory B cells are already available, can differentiate into plasma cells
- Produce large amounts of IgG (antibodies)
- Quickly overcomes the infection
22
Q
describe the cell mediated response
A
- Involves T-Cytotoxic Cells (also known as Tc or CD8+ cells)
- Each Tc cell has a T-cell receptor (TCR) for one specific antigen
- Begins when an infected antigen presenting cell processes and presents endogenous antigen (foreign antigen produced inside a body cell) along with MHC class I
- Presented antigen contacts Tc cell’s TCR
- If the antigen matches the TCR, the Tc cell will be activated to divide and differentiate into:
- Memory Tc cells
- Effector Tc cells (almost at point where they can kill infected body cells but not yet)
23
Q
what are the two types of cells the Tc cells differentiate into in the cell mediated response?
A
- Memory Tc cells
- Effector Tc cells
24
Q
What happens after the Tc cell differentiates into Memory Tc cells and effector Tc cells?
A
- Effector Tc cells must be further activated by a Th1 cell
-effector Tc becomes a cytotoxic cytotoxic T lymphocyte (CTL) - CTL circulates in blood and tissues and searches for other body cells that present that specific antigen along with MHC class I
- If it finds one, it secretes:
-Perforins -enzymes that poke holes in infected cell’s membrane
-Granzymes -enzymes that promote apoptosis
(programmed cell death) - destroying the abnormal or infected cell
25
how do dendritic cells link humoral, cell-mediated and innate immunity together?
* Dendritic cell phagocytizes an intruder (innate)
* Presents exogenous antigen on MHC class II to Th cell
* Activates Th cell to multiply and differentiate:
-Th1, Th2, Th17, memory Th cells
## Footnote
Th1 > cell-mediated (activate effector Tc cells to become cytoxic T lymphocyte (CTL) , Th2 > humoral (activate B cells and antibodies), Th17 > (part of adaptive but communicates to innate immune system by recruiting neutrophils)
26
how do B cells link humoral, cell-mediated and innate immunity together
* B cell encounter intruder (present antigens)
* Th2 cells secrete signals to activate B cell
* B cell differentiates into memory and plasma cells
* Produce and secrete large amounts of antibody
27
If an antigen can multiply inside of dendritic cell (endogenous antigen) how does it link humoral, cell-mediated and innate immunity together
* Presented on MHC class I (dendritic is part of innate)
-activates a Tc cell
* Th1 cell secretes chemicals to further activate the Tc cell (cell-mediated)
* Differentiates into CTL
-destroy infected body cells
* Th17 cells recruit and activate neutrophils (increased phagocytosis- innate)
-links adaptive and innate immunity
