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MCAT: The Immune System
Terms in this set (92)
Is composed of defenses that are always active against infection, but lack the ability to target specific invaders over others. It is also called nonspecific immunity
Also called specific immunity. Refers to the defenses that target a specific pathogen. This system is slower to act, but can maintain immunological memory of an infection to be able to mount a faster attack in subsequent infections
Bone Marrow in Immune System Function
It produces all of the leukocytes (white blood cells) that participate in the immune system through the process of hematopoiesis
Is a storage area for blood, filters blood and lymph, and is a site where immune responses can be mounted
Specific immunity produced by B cells that produce antibodies that circulate in body fluids
A class of adaptive immune cells, mature in the thymus, a small gland just in front of the pericardium, the sac that protects the heart. They are agents of cell mediated immunity because they coordinate the immune system and directly kill virally infected cells
Thymus Immune System Function
It is a small gland just in front of the pericardium, the sac that protects the heart and produces T-cells
Produces antibodies in response to antigens
Provide a place for immune cells to communicate and mount an attack; B-cells can be activated here. They filter lymph. They are small, bean-shaped structures along the lymphatic vessels.
Gut-Associated Lymphoid Tissue (GALT)
Include the tonsils and adenoids in the head, Peyer's patches in the small intestine, and lymphoid aggregates in the appendix. Protect from potential invasion through the digestive system.
Form a protective circle of lymphatic tissue around the entrance to the respiratory system
Lymphoid tissue located behind the nasal cavity
Collections of lymphatic tissue found in the submucosa of the small intestine
Material added at the end of a book
A group of leukocytes containing granules in their cytoplasm; neutrophils, eosinophils, basophils.
Are located in the cytoplasm of granulocytes. They contain toxic enzymes and chemicals, which can be released by exocytosis, and are particularly effective against bacteria, fungal, and parasitic pathogens
A group of leukocytes without granules in their nuclei; lymphocytes, monocytes.
Hematopoietic Stem Cells
The stem cells that give rise to all the other blood cells; hemocytoblasts
Agranulocytes that are responsible for antibody production, immune system modulation, and targeted killing of infected cells
Are phagocytic cells in the bloodstream, are also considered agranulocytes
Monocytes in tissues.
Divisions of Specific Immune System
1) Humoral immunity
2) Cell-mediated immunity
Immunity provided by T-cells
A type of white blood cell that engulfs bacteria by phagocytosis. They are the most populous leukocyte in blood and are very short-lived
White blood cell that are responsible for combating infection by parasites and are involved in allergic reactions. Upon activation, eosinophils release large amounts of histamine, an inflammatory mediator. This results in vasodilation and increased leakiness of the blood vessels, allowing additional immune cells (especially macrophages and enutrophils) to move out of the blood-stream and into the tissue.
They contain large purple granules and are involved in allergic responses. They are the least populous leukocyte in the bloodstream under normalconditions
Antibacterial enzymes found on the skin.
Skin Immune System Function
It provides a physical barrier between the outside world and out internal organs, excluding most bacteria, viruses, fungi, and parasite form entering the body
An enzyme found in saliva and sweat and tears that destroys the cell walls of certain bacteria
Consists of a number of proteins in the blood that act as nonspecific defense against bacteria. They punch holes in the cell walls of bacteria
Classical Pathway (Complement System)
Requires the binding of an antibody to a pathogen to activate the complement system
Alternative Pathway (Complement System)
Does not require antibodies to activate the complement system
Are proteins that are produced by cells that have been infected with viruses. These proteins prevent viral replication and dispersion. They cause nearby cells to decrease production of both viral and cellular proteins. They also decrease the permeability of these cells, making it harder for a virus to infect them.
Permanent, rather than transient cell group in a tissue. For example: macrophages.
Gastrointestinal Tract Immune System
Plays a role in nonspecific immunity. The stomach secretes acid, resulting in the elimination of most pathogens. The gut is colonized by bacteria which can outcompete with many pathogens for survival.
1) It phagocytizes the invader through endocytosis
2) It digests the invader using enzymes
3) It presents little pieces of the invader (mostly peptides) to other cells using a protein called major histocompatibility complex (MHC)
4) Release cytokines which are chemical substances that stimulate inflammation and recruit additional immune cells in the area
Major Histocompatibility Complex (MHC)
Cell surface proteins that distinguish between self and non self
Chemical substances that stimulate inflammation and recruit additional immune cells in the area
The MHC-1 pathway because it binds antigens from inside the cell. Cells that have been invaded by intracellular pathogens can then be killed by a certain group of T-cells to prevent infection of other cells
MHC class I
Are a type of MHC where any protein produced within a cell can be loaded onto MHC-I and be presented on the surface of the cell allowing the immune system to monitor the health of these cells and to detect if the cells have been infected with a virus or another intracellular pathogen
Is a substance (usually a pathogenic protein) that can be targeted by an antibody
Include macrophages, dendritic cells in the skin, some B-cells, and certain activated epithelial cells. They contain MHC class II molecules.
MHC class II
Found on macrophages, dendritic cells, and B cells, it presents pathogens from the environment
Pathway that antigen presented on Class II MHC takes
Adaptive Versus Innate Cells in Immune System
1) Innate: macrophage, mast cell, granulocytes, dendritic cell, natural killer cell
2) Adaptive: B-cell, T-Cell
This cell releases histamine and other chemicals that promote inflammation. They are closely related to basophils, but have smaller granules and exist in the tissues, mucosa, and epithelium
Pattern Recognition Receptors (PRR)
PRRs are able to recognize the category of the invader (bacterium, virus, fungus, or parasite). They are on macrophages and dendritic cells
Toll-like Receptors (TLR)
Membrane-bound receptors on extracellular phagocytic cells (macrophages, neutrophils, DCs)
Histamine Affect on the Body
It causes inflammation by inducing vasodilation and the movement of fluid and cells form the bloodstream into tissues
Natural Killer Cells
A type of nonspecific lymphocyte that is able to detect the downregulation of MHC and induce apoptosis in these virally infected cells. Cancer cells may also down-regulate MHC production, so NK cells also offer protection form the growth of cancer as well
Cell movement that occurs in response to chemical stimulus
When a specific antigen is bound to an antibody and it attracts other leukocytes to phagocytize those antigens immediately
Result from dead neutrophil collections form this during infection
It presents antigens-fragments of protein or other molecules form pathogens or cancer cells-to adaptive immune cells, inducing the cells to attack bearers of the displayed antigens
Occurs in the bone marrow
Occurs in the thymus
Where are the Cells of the Immune System Created
All cells of the immune system are created in the bone marrow, but B- and T-cells mature in different locations
When antibodies cause pathogens to clump together, forming large insoluble complexes that can be phagocytized
Occurs when an antigen binds to antibodies on the surface of a mast cell. It is the exocytosis of granule contents, allowing the release of histamine and causing an inflammatory allergic reaction
What will an Antibody do when Bound to an Antigen
1) opsonization: antibodies attract other leukocytes to phagocytize those antigens immediately
2) Agglutinate: antibodies cause pathogens to clump together, forming large insoluble complexes that can be phagocytized
3) Antibodies can block the ability of a pathogen to invade tissues, essentially neutralizing it
Clonal Selection (B-Cells)
Only B-cells that can bind to the antigen with high affinity survive, providing a mechanism for generating specificity
Constant Region (Domain)
It is the region of the antibody that cells such as natural killer cells, macrophages, monocytes, and eosinophils have receptors for, and that can initiate the complement cascade
Switch from producing IgM / IgD to another Ig isotype after antigen stimulation
Are Y-shaped molecules that are made up of two identical heavy chains and two identical light chains. Disulfide linkages and noncovalent interactions hold the heavy and light chains together
Variable Region (Domain)
That region of antibodies that varies from one antibody to another even within one class. It allows the antibody to bind to different antigens.
Those that have not yet been exposed to an antigen, they wait in the lymph nodes for their particular antigen to come along
What Happens when Naive B-Cells Meet an Antigen
They will proliferate and produce: plasma cells and memory B-cells.
Cells that develop from B cells and produce antibodies.
They stay in the lymph node, awaiting reexposure to the same antigen
Primary Response (Immune System)
When an antigen is first recognized by a naive B-call it produces the Plasma cells and memory B-cells. It takes approximately seven to ten days.
Secondary Response (Immune System)
Occurs if the same microbe is ever encountered again, the memory cells jump into action and produce the antibodies specific to that pathogen. This immune response is more rapid and robust than the primary response.
Positive Selection (Cytotoxic Immunity)
Refers to maturing only cells that can respond to the presentation of antigen on MHC (cells that cannot respond to MHC undergo apoptosis because they will not be able to respond to the periphery)
Negative Selection (Cytotoxic Immunity)
Refers to causing apoptosis in cells that are self-reactive (activated by proteins produced by the organism itself)
A peptide hormone secreted by the thymic cells that helps facilitate the maturation of T-cells
Are chemicals that are capable of recruiting other immune cells (such as plasma cells, cytotoxic T-cells, and macrophages). They are secreted by Helper T-cells
Helper T-Cells/ CD4+ T-Cells
Coordinate the immune response by secreting chemicals known as lymphokines. They respond to antigens presented on MHC-II molecules. Because MHC-II presents exogenous antigens, CD4+ T-cells are most effective against bacterial, fungal, and parasitic infections
What Type of MHC does CD4+ Versus CD8+ Respond to?
1) CD4+ cells respond to MHC-II (4*2=8)
2) CD8+ cells respond to MHC-I (8*1=8)
Cytotoxic T-cells (Tc or CTL)/ CD8+ T-cells
Are capable of directly killing virally infected cells by injecting toxic chemicals that promote apoptosis into the infected cell. CD8+ T-cells respond to antigens presented on MHC-I molecules.
They also express CD4, but can be differentiated form helper T-cells because they also express a protein called Foxp3. These cells help to tone down the immune response once infection has been adequately contained. These cells can also turn off self-reactive lymphocytes to prevent autoimmune diseases: this is termed self tolerance
When a Reuglatory T-cell turns off self-reactive lymphocytes to prevent autoimmune diseases.
Created by the helper t-cell, remembers pathogen to have a more powerful and quicker response
Are the proteins and carbohydrates present on the surface of every cell of the body
When the immune system fails to make the distinction between self and foreign, and it attacks cells expressing particular self-antigens
Allergies and autoimmunity towards non-dangerous antigens.
The immune system is stimulated to produce antibodies against a specific pathogen
Results from the transfer of antibodies to an individual. The immunity is transient because only the antibodies, and not the plasma cells that produce them, are given to the individual
The major duct of the lymphatic system
Abnormal accumulation of fluid in interstitial spaces of tissues. Results in swelling.
Equalization of Fluid Distribution (Lymphatic Vessels)
Hydrostatic and oncotic pressure determine the quantity of fluid that leaves the tissues. The net pressure drawing fluid in at the venule end is slightly less than the net pressure pushing fluid out at the arterial end, a small amount of fluid remains in the tissues. So lymphatic vessels drain these tissues and subsequently return the fluid to the bloodstream
Are sites within secondary lymphoid organs - lymph nodes and the spleen where mature B cells proliferate, differentiate, and mutate their antibody genes (through somatic hypermutation aimed at achieving higher affinity), and switch the class of their antibodies
Small lymphatic vessels, are located at the center of each villus in the small intestine. Fats, packaged into chylomicrons by intestinal mucosal cells, enter the lacteal for transport to the bloodstream
Lymphatic fluid carrying many chylomicrons. It takes on a milky white appearance.
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