Immune and Lymphatic System I Flashcards
What is innate immunity?
immunity that lacks specificity and memory. Neutrophils are the first responders.
What is acquired immunity?
immunity that has specificity and memory. It takes longer to develop and includes humoral immunity.
What cells are highly involved in innate immunity?
neutrophils
What is passive immunity?
temporary immunity due to donated antibodies.
What is active immunity?
long lasting/permanent immunity due to self exposure to antigen resulting in memory T cells and B cells specific for antigen.
What is humoral immunity?
Antibody mediated immunity; it includes the use of plasma cells.
What is cell-mediated immunity?
T cells, B cells and antigen-presenting cells
What is lymphoid tissue?
Tissue that appears in the body as a gradient from diffuse lymphoid tissue to aggregated lymphoid tissue to lymphoid organs.
What are the two types of lymphoid organs?
primary and secondary
What are primary lymphoid organs?
Thymus and the bone marrow. Precursor cells in this region mature into immunocompetent cells. Each cell is programmed to recognize a specific antigen.
Where do lymphocytes originate?
in primary lymphoid organs. They then take up residence in secondary lymphoid organs.
What are features of lymph follicles?
they are not enclosed within a capsule, occur singly or in aggregates, are sites of B cell localization and proliferation, and are transient.
What do primary follicles contain?
virgin B cells and dendritic reticular cells that have not been exposed to antigens.
What are secondary follicles?
follices derived from primary follicles that have been exposed to nonself antigens. They are not present at birth.
What are the two major regions of a secondary follicle?
the cortex (corona) and the germinal center.
What does the corona contain?
densely packed B lymphocytes.
What does the germinal center contain?
B lymphocytes, memory B cells, plasma cells, dendritic reticular cells.
What is diffuse lymphoid tissue made up of?
scattered clusters of plasma cells, macrophages and lymphocytes located in the connective tissue stroma and various other sites.
Where is aggregated lymphoid tissue found?q
beneath and in contact with the epithelium.
What are the 3 accessory cells (antigen-presenting cells)?
macrophages, dendritic cells and follicular dendritic cells
Where do all immune system cells originate?
in the bone marrow.
What protein activates pro-B cells?
interleukin-7
What does a pre-B cell receptor express after it is activated by interleukin-7?
pre-B cell receptor.
What makes up the B lymphogute antigen receptor complex?
Igbeta, IgAlpha, ITAM
If a self-antigen binds strongly to a B cell, what occurs?
The B cell undergoes apoptosis.
If a self antigen does not bind strongly to a B cell, what occurs?
it survives and enters blood circulation.
The maturation of B cells involves the appearance of what cell surface receptors?
IgM and IgD, MCH class II proteins, complement receptors, Ig Fc receptors.
What are the 5 classes of antibodies?
IgA, D, G, M, E
What is the Fab fragment of an antibody?
The part of the antibody that recognizes the antigens. It is highly variable.
That is the Fc fragment of an antibody?
The part of the antibody that binds to a cell membrane.
Where are IgA antigens found?
saliva, milk, GI and respiratory tracts.
Where are IgD antigens found?
the surface of B cells traveling to lymphoid organs.
Where are IgG antigens found?
blood. It is responsible for most antibody activity.
Where are IgM antigens found?
in developing B cells.
Where are IgE antigens associated with?
allergic responses.
What is the function of the major histocompatibility complex?
The presentation of antigenic peptides to T cells. Antigen-presenting cells phagocytize antigens and bind the fragments to major histocompatibility complex molecules.
Where are MHC I cells expressed?
On the surface of all cells except trophblast and red blood cells.
Where are MHC II cells expressed?
On the surface of B cells and antigen-present cells.
What to CD8+ cells recognize?
peptide fragments of foreign proteins bound to MHC class I on the surface of cells.
What do CD4+ T cells recognize?
peptide fragments of foreign proteins bound to MCH class proteins on the surface of cells.
What type of T cells recognizes antigens bound to MHC class II molecules?
CD4+ T cells.
What are helper cells?
cells that assist CD8+ cell differentiation and B cell differentiation.
What are CD8+ T cells also known as?
cytolytic cells.
What do CD8+ T cells do?
bind to an antigen-presenting cell. They undergo mitosis and release perforins and fas ligand. They recognize MHC class I molecules and are mediators of cell immunity.
What are perforins?
proteins released by CD8+ T cells that punch holes in the membranes of cells, especially if they are infected by a virus. It causes cell death.
What is a fas ligand?
a ligand that triggers signaling for apoptosis. They also proliferate in the membrane.
What are CD16+ T cells also known as?
natural killer cells.
What are CD16+ cells activated by?
tumor cell antigens (inteferon-gamma).
What stimulates the proliferation of NK cells?
interleukin-2.
What phagocytizes foreign material?
macrophages.
What are expressedon the sufrace of macrophages bound to MHC-II?
antigens.
What does the MCH-II antigen coplex do?
it is presented to activated helper T cells, which then undergo mitosis.
Activated T cells can undergo what two types of differentiation?
memory cells or cells that secrete interleukins.
What type of cells do T cells attract?
B cells.
Activated B cells undergo what two types of differentiation?
plasma cells or memory cells.
What is the complement system?
An array of about 20 serum proteins which are synthesized in the liver and found in the blood.
What is the classic pathway of the complement system?
a pathway that is activated by antibodies binding to a pathogen.
What is the alternate pathway of the complement system?
A pathway that is directly activated by the pathogen.
What does the compementary system facilitate?
inflammatory responses.
What does the complement cascade involve?
coating the pathogen with complement initiating the cascade.
C1 is made up of what three subcomponents?
C1q, C1r, C1s
What is the activation of the classical complement pathway?
C1q + Fc -> C1r -> C1s
What is the activation sequence of the classical complement pathway? (Starting at C1s)
C1s -> c4 -> C4a + C4b C4b binds to surface of pathogen C1s -> C2 -> C2a + C2b C2b binds to C4b -> C4b-2b complex = C3 (convertase)
What is the activation sequence of the classical complement pathway (starting at C3)?
Multiple C3b bind to C3 convertase
C5 binds to C3b -> C5a + C5b
When C6, C7 and C8 are added, they form pores in the membrane of the pathogen.
What does the complement cascade result in?
activation of the membrane attack complex on the pathogen, leading to perforation and lysis. The productionof opsonins (coatings that make the antigens more palapatable to phagocytes) and the release of chemotactic agents (chemokines) that attact phagocytes to the areas of infection or inflammation.
What is the parenchyma of the lymph node?
tightly packed cells. They are mostly lymphocytes.
What is the stroma of the lymph node?
reticular fibers and cells, including undifferentiated cells and fixed and free macrophages.
What is the hilus of the lymph node?
the entry and exit point for vessels. Efferent lymphatic vessels as well as arteries and veins leave through here.
What is the capsule?
A region of dense collagen fibers, elastic fibers and smooth muscle fibers.
What are the two regions of the cortex of the lymph node?
the outer cortex and follicles.
What do the follicles of the cortex of the lymph node contain?
B cells, follicular dendritic cells and migrating t cells.
What are the components of the secondary follicles?
a mantle and germinal center (proliferating T cells).
What does the primary follicle of the cortex lack?
a mantle
What does the inner part of the cortex contain?
Th cells, macrophages and high endothelial venules.
What are high endothelial venules?
They are par of the inner cortex of a lymph node. They are a port of entry for circulting differentiated lymphocytes to seed lymph node.
What is the medulla of the lymph node?
Irregular arrangement of loose medullary sinuses and dense medullary cords. Sinuses are lined with macrophages, and cords consists of blood vessels, lymphoblasts and plasma cells.
What is the site of lymphocyte reentry into the bloodstream?
the medulla
