Lecture 2: Cells and Tissues of the Adaptive Immune System Flashcards
T cells mature under the influence of the thymus and, on stimulation by Ag, give rise to what?
cellular immunity
B cells mature mainly in the bone marrow and give rise to?
humoral immunity
What is humoral adaptive immunity mediated by?
Mediated by Abs in the blood and mucosal secretions which are produced by B cells.
What is humoral adaptive immunity the principal defense against?
Against Extracellular Microbes and their toxins because secreted Abs can bind to these microbes and toxins and assist in their elimination.
What is CMI controlled by?
Responses of T cells which often function in concert with Ag-presenting cells and phagocytes to eliminate microbes.
What is the main function of CMI?
The killing of infected cells to eliminate reservoirs of infection.
True or False:
Helper T cells also help B cells make effective Abs thus contributing to eradication of extracellular microbes.
True
In CMI, what do T helper cells do?
- activate macrophages (IFN-gamma) to kill phagocytized microbes.
- activate cytotoxic T lymphocytes to directly destroy infected cells.
Which T helper cell activates macrophages?
Th1
Which T helper cell is involved in inflammation?
Th17
Which T helper cell is involved in activation (proliferation and differentiation) of T and B cells?
Th2
What do regulatory T cells do?
Suppress and prevent immune responses (e.g., to self antigens).
What do cytotoxic T cells do?
recognize Ags on infected cells and kill these cells
What do B cells do?
recognize soluble Ags and develop into Ab-secreting cells
What do T helper cells do?
recognize Ags on the surfaces of Ag-presenting cells and secrete cytokines, which stimulate different mechanisms of immunity and inflammation
What is the functional significance of specificity in adaptive immunity?
Ensures that the immune response to a microbe (or nonmicrobial Ags) is selective to that microbe (or Ag).
What is the functional significance of diversity in adaptive immunity?
Enables the immune system to respond to a large variety of Ags.
What is the functional significance of memory in adaptive immunity?
Increases the ability to combat repeat infections by the same microbe.
What is the functional significance of clonal expansion in adaptive immunity?
Increases the number of Ag-specificlymphocytes to keep pace with microbes.
What is the functional significance of specialization in adaptive immunity?
Generates responses that are optimal for defense against different types of microbes.
What is the functional significance of contraction and homeostasis in adaptive immunity?
Allows the immune system to recover from one response so that it can effectively respond to newly encountered Ags.
What is the functional significance of nonreactivity to self in adaptive immunity?
Prevents injury to the host during responses to foreign Ags.
What is the clonal selection hypothesis?
According to this hypothesis, Ag-specific clones of lymphocytes develop before and independent of exposure to Ag.
List the order of immunologic memory?
> an immune response eliminates the microbes that initiated the response.
> the expanded lymphocyte clones die in a contraction phase and homeostasis is restored.
> a few activated lymphocytes become Ag-specific memory cells which may survive for years after the infection.
True or False:
Generation of memory responses is important goal of vaccination.
True
Active Immunity?
Is conferred by host response to a microbe or microbial Ags.
- provides resistance to infection and are specific for microbial Ags
- responses generate immunologic memory
Passive Immunity?
Is conferred by adoptive transfer of antibodies or T lymphocytes specific for the microbe.
- provides resistance to infection and are specific for microbial Ags.
- NO memory
What does CD stand for?
Cluster of Differentiation - which indicates a defined subset of cellular surface receptors that identify cell type and stage of differentiation.
Secondary Lymphoid Organs
> spleen
lymph nodes
mucosa-associated lymphoid tissue
Primary Lymphoid Organs
> thymus
> bone marrow
How long do naive lymphocytes live if they do not recognize Ag?
1 - 3 months
True or False:
Ag-specific receptors structure varies from one cell to another but they are all identical on a single cell.
True
Where are developing T cells found in the thymus?
thymic medulla
True or False:
T cells are produced primarily early in life.
True
What cytokines have an important role in T cell development?
IL-1
IL-2
IL-6
IL-7
What does the development of B cells involve contact with?
Stromal Cells
IL-1
IL-6
IL-7
Where do the circulating lymphocytes never reach in the body?
eye
brain
testicles
What specialized endothelium of postcapillary venules do lymphocytes enter the LN through?
HEV (high endothelium venules)
How do lymphocytes transmigrate into the tissue?
By diapedesis in response to chemokines.
Through which vessel do DCs enter the LN?
afferent lymphatic vessel
What are the 3 professional APCs?
- DCs
- Tissue Macrophages
- B cells
Do B cells need an APC?
No - only T cells.
Which professional APC is the only one that can present and activate naive T cells in the LN?
DCs
What can macrophages and B cells present Ags to?
effector T cells, but not naive T cells.
Which two professional APCs are cells of innate immunity and provide a link between innate and adaptive immunity?
DCs
Macrophages
How do DCs acquire Ags?
> phagocytosis
receptor-mediated endocytosis
pinocytosis
Can activated DCs also secret cytokines?
Yes
Where do classical DCs reside?
Skin, mucosa, and organ parenchyma.
What type of DC is an early cellular responder to viral infections?
Plasmacytoid DCs
How do plasmacytoid DCs respond to viral infections?
The recognize nucleic acids of intracellular viruses and produce soluble proteins - IFN alpha/beta, which has potent antiviral activities.
True or False:
Follicular Dendritic Cells (FDCs) bind and display unprocessed Ags on their surfaces for recognition by B cells only.
True
Where do FDCs reside?
> LNs
Spleen
Mucosal lymphoid tissues
