introduction to immunology Flashcards
Types of Lueckocytes
1- Lymphoid cells ( T, B and Nk)
2- Myeloid cells ( macrophage, neutrophils and platelets, basophils, monocytess and phagocytes)
properties of adaptive immunity
Specificity and diversity
Memory
Clonal expansion
specialization
contraction and homeostasis
Nonreactivity to self
Cells of adaptive immunity
1- T and B cells
2- APC
3- Effector cells ( T cells, macrophages and granulocytes)
Where do B lymphocytes mature?
In the bone marrow
Where do T lymphocytes mature?
In the thymus
What are the generative (or central) lymphoid organs?
Sites where mature lymphocytes are produced
What happens to mature lymphocytes after leaving the generative lymphoid organs?
They enter circulation and peripheral (secondary) lymphoid organs
What is the major site of immune responses?
Peripheral (secondary) lymphoid organs
What are effector lymphocytes?
Differentiated progeny of naive cells that can eliminate antigens
What are plasma cells?
Antibody-secreting cells developed from B lymphocytes in response to antigenic stimulation
What are plasmablasts?
Antibody-secreting cells found in the blood that can migrate to the bone marrow
What is the function of cytokines produced by effector CD4+ T cells?
Activate B cells, macrophages, and other cell types
What do effector CD8+ T cells do?
Kill infected host cells
What happens to effector cells as the antigen is eliminated?
They are short-lived and die
What are memory cells?
Cells that can survive long periods in the absence of antigen
How does the frequency of memory cells change with age?
It increases due to exposure to environmental microbes
What are the common portals of entry for microbes?
Skin, gastrointestinal, respiratory, and genitourinary tracts
Which cells are the most specialized antigen-presenting cells in the immune system?
Dendritic cells
What role do dendritic cells play in the immune response?
Dendritic cells capture protein antigens of microbes, transport them to lymph nodes, and display fragments for T lymphocyte recognition.
They are crucial for initiating T cell responses.
How do dendritic cells present antigens to T lymphocytes?
They capture antigens and display protein fragments in regional lymph nodes for recognition by T lymphocytes.
This process is essential for T cell activation.
What types of cells can capture microbes or their antigens in lymphoid organs?
Dendritic cells and macrophages.
These cells reside in lymphoid organs and present antigens to lymphocytes.
What are costimulators in the context of T cell activation?
Surface proteins produced by dendritic cells that are required, along with antigen, to activate naive T lymphocytes.
They enhance the effectiveness of T cell responses.
Why are dendritic cells considered the most potent stimulators of naive T cells?
They express higher levels of costimulatory proteins than other cell types.
This makes them efficient initiators of T cell responses.
How do B lymphocytes recognize antigens?
B lymphocytes may directly recognize antigens of microbes, either released or on their surface.
This is a key aspect of humoral immunity.
What role do follicular dendritic cells (FDCs) play in the immune response?
FDCs reside in germinal centers and display antigens that stimulate the differentiation of B cells.
They are distinct from dendritic cells that present antigens to T cells.
True or False: Follicular dendritic cells present antigens to T cells.
False.
FDCs do not interact with T cells; they specifically stimulate B cell differentiation.
Fill in the blank: Dendritic cells are the most efficient initiators of _______.
T cell responses.
This is due to their unique ability to present antigens and provide costimulatory signals.
What are the two main types of lymphoid organs in the immune system?
The two main types of lymphoid organs are generative lymphoid organs and peripheral lymphoid organs.
What is the role of generative lymphoid organs?
Generative lymphoid organs are where T and B lymphocytes mature and become competent to respond to antigens.
What is the function of peripheral lymphoid organs?
Peripheral lymphoid organs initiate adaptive immune responses to microbes.
What are the major peripheral lymphoid organs?
The major peripheral lymphoid organs include lymph nodes, the spleen, and the mucosal and cutaneous immune systems.
How do peripheral lymphoid organs promote immune responses?
They are organized to enable antigen-presenting cells (APCs) to concentrate antigens and help lymphocytes locate and respond to them.
What is the primary function of lymph nodes?
Lymph nodes sample antigens from lymph and help lymphocytes respond to these antigens.
What is the role of the spleen in the immune system?
The spleen captures and concentrates blood-borne antigens, similar to the role of lymph nodes for lymph-borne antigens.
What are mucosal and cutaneous immune systems?
They are specialized collections of lymphoid tissues and APCs located in and under the epithelia of the skin and the gastrointestinal and respiratory tracts.
What are tonsils and Peyer patches?
Tonsils in the pharynx and Peyer patches in the intestine are examples of anatomically defined mucosal lymphoid tissues.
What is a germinal center?
A germinal center is a lightly staining region in a follicle that plays an important role in the production of highly effective antibodies.
How are T and B lymphocytes organized in lymph nodes?
B lymphocytes are concentrated in follicles around the cortex, while T lymphocytes are located in the paracortex.
What attracts B lymphocytes to follicles?
B lymphocytes are attracted to follicles by chemokines secreted by follicular dendritic cells (FDCs).
What chemokine receptor do naive T lymphocytes express?
CCR7
What is the role of CCR7 in naive T lymphocyte migration?
It recognizes chemokines produced in the paracortex of lymph nodes and periarteriolar lymphoid sheaths of the spleen
What happens to B cells and T cells after they are activated by antigens?
They migrate toward each other and meet at the edge of follicles
How do effector T cells exit lymph nodes?
Through efferent lymphatic vessels
Where do activated T cells go after leaving lymphoid organs?
They end up in the circulation and can go to distant sites of infection
What are high endothelial venules (HEVs)?
Specialized postcapillary venules that naive T lymphocytes use to enter lymph nodes
What chemokine receptor do naive B cells express?
CXCR5
What is the fate of naive cells that do not encounter specific antigens in lymph nodes?
They leave the lymph nodes and reenter the circulation
What do effector T cells preferentially migrate to?
Tissues infected by microbes
Where do most antibody-secreting plasma cells migrate to?
The bone marrow or mucosal tissues
True or False: The spleen contains high endothelial venules (HEVs).
False
