Term
| main sites of hematopoiesis |
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Definition
| The sternum, vertebrae, iliac bones and ribs are the main sites of hematopoiesis |
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Term
| Cells of the immune system are derived from |
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Definition
| Cells of the immune system are derived from pluripotent hematopoietic stem cells in the bone marrow in the adult and the liver in the fetus |
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Term
| Leukocytes are involved in |
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Definition
| Leukocytes (white blood cells) are involved in either innate or adaptive immunity or both depending on the cell |
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Term
| Neutrophils, Granulocytic neutrophils, Polymorphonuclear neutrophils (PMNs) |
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Definition
Have a lobed nucleus and granulocytes
Are the most abundant leukocyte in the blood
Are the first cells to arrive at inflammation
Are phagocytes
Their granules contain many antimicrobial agents |
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Term
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Definition
Polymorphonuclear granulocytes
Main defensive job is against parasites
Increased numbers in the blood are indicators of allergy
Have surface receptors for antibodies (IgE) responsible for immediate hypersensitivity (allergies such as hay fever)
When IgE antibodies react with surface receptors, degranulation occurs
Degranulation contributes to the manifestations of immediate hypersensitivity diseases such as hay fever |
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Term
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Definition
Polymorphonuclear granulocytes
Have surface receptors for antibodies (IgE) responsible for immediate hypersensitivity (allergies such as hay fever)
When IgE antibodies react with surface receptors, degranulation occurs
Degranulation contributes to the manifestations of immediate hypersensitivity diseases such as hay fever |
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Term
| Monocytes and Macrophages |
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Definition
Are phagocytes
Monocytes circulate in the blood, and when they enter tissue, mature into macrophages
Monocytes arrive at inflammation after PMNs
Are effectors in both innate and adaptive immunity
Recruit other cells to inflammation
Present antigens to T cells for the cellular immune response
Have surface receptors for antibodies that are attached to pathogens enhancing phagocytosis |
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Term
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Definition
Large macrophages found in most soft tissue
Especially found in lymph nodes and spleen
Are especially important as APCs to T cells |
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Term
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Definition
Are the cells that specifically recognize and respond to antigens in the adaptive immune response
As stem cells develop into lymphocytes, three different types of lymphocytes are recognized |
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Term
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Definition
| T lymphocytes (T Cells): The T stands for thymus where further development occurs |
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Term
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Definition
| B lymphocytes (B cells): The B stands for bursa or bone marrow |
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Term
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Definition
| Natural killer (NK) cells: kill distressed cells without DNA rearrangement |
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Term
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Definition
In the bone marrow, B cell development of specific antigen receptors is antigen independent and due to DNA rearrangement
Immature B cells, developing in the bone marrow, undergo apoptosis upon recognition of self antigens
B cell activation into antibody producing, then antibody secreting plasma cells is antigen dependent
Each B cell can have thousands of receptors on its surface that are specific for the same antigen
Depending on the type of antigen presented to the B cell, B cells can proliferate by themselves or they need to interact with T cells to proliferate
B cells that interact with T cells gain the ability to switch from IgM, the first antibody produced to IgG or other antibody classes (isotypes)
B cells that react with T cells also develop into antibody secreting plasma cells or B memory cells that live for years. |
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Term
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Definition
Immature T cells home to the thymus and are called thymocytes while they mature
T cells develop their antigen specific receptors in the thymus independent of antigenic stimulation via DNA rearrangement
T cells are selected for maturation only if their T cell receptors (TCRs) do not react with self
T cells are important in regulating the adaptive immune response, are responsible for cell mediated immunity and help certain B cells to produce antibody and mature into plasma cells |
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Term
| Clusters of Differentiation(CDs) |
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Definition
In immunology, CDs refer to surface molecules on leukocytes with specific functions.
CDs are often used as identifying markers for a subpopulation of cells
These markers are proteins that have specific functions
Immunologists often refer to cells by their CD designation, ex. that batch of cells are CD4 positive or those are CD4 cells |
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Term
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Definition
Express CD4 and are often called CD4 cells
Regulate antigen-directed effector functions in cell mediated immunity
Stimulate B cells to proliferate , undergo isotype switching and differentiate into antibody producing cells
Recognize antigen complexed with MHC class II molecules on dendritic cells, macrophages , monocytes and B cells |
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Term
| Cytotoxic T Lymphocytes (CTLs) |
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Definition
Express CD8 and are often called CD8 cells
Are cytotoxic to host cells infected with intracellular pathogens (viruses) and to tumor cells
Are cytotoxic in an antigen specific manner dependent upon the expression of MHC I molecules that are expressed on all nucleated cells in the body |
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Term
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Definition
Are where leukocytes originate, mature, differentiate and proliferate
Are divided into primary and secondary organs based on the processes that occur in these organs |
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Term
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Definition
Primary lymphoid organs are the site where stem cells develop into leukocytes
The liver in the fetus and bone marrow in adults is the site of the origin of leukocytes
Because of recirculation, the bone marrow also functions as a secondary lymphoid organ
The thymus reaches maturity prior to puberty and then slowly loses function
The thymus is situated in the anterior mediastinum
The primary function of the thymus is to educate T cells to differentiate between self antigens and non-self antigens
The thymus is the site of T cell maturation |
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Term
| Secondary Lymphoid Organs |
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Definition
The secondary lymphoid organs are the major areas where lymphocytes come in contact with antigens
Lymph nodes and spleen are the most important secondary organs
Next of importance are the MALTS or mucosa associated lymphoid tissues found lining the digestive and respiratory tracts |
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Term
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Definition
The spleen is located in the left upper quadrant of the abdomen
The spleen acts as a filter in the blood and is the major site of immune responses to antigens in the blood
It contains areas for T and B cells
APCs are found in areas called germinal centers and present antigens to the lymphocytes in these areas |
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Term
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Definition
The lymphatics are a network of thin tubes that drain interstitial fluid from the body and eventually return it to the circulatory system
There are many lymph nodes in the body where filtration of the lymph takes place.
APCs reside in the nodes, collect antigens brought to the nodes from the tissues and present them to the T and B cells |
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Term
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Definition
Aggregates of lymphoid tissue that reside along the respiratory and digestive tracts comprise the MALTS
In general, they play the same kind of role as lymph nodes, but are active in delivering antigens in the respiratory and digestive tracts to the lymphocytes |
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