Term
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Definition
| the study of physiological mechanisms that are used to defend the body from invasion by foreign or infectious agents |
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Term
| The Four Kinds of Pathogen that Cause Human Disease |
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Definition
| Bacteria, Fungi, Parasites, and viruses |
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Term
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Definition
| (Innate) - Series of proteins that act to tag an invader for uptake (phagocytosis) by other immune cells or by poking holes in the microbe by completing the complement cascade. |
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Term
| Immune Defense-Innate Vs. Adaptive Immunity |
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Definition
Innate immune system
Is the first line of defense against infections
It works rapidly
Gives rise to the acute inflammatory response
Has some specificity for microbes
Adaptive immune system
Takes longer to develop
Is highly specific for antigens, including those associated with microbes
Primary immune response = first time the adaptive immune response is activated against a pathogen.
Secondary immune response = any time the adaptive immune response is activated against a pathogen that it has been exposed to before
Remembers that it has encountered a microbe previously
(i.e. shows memory) |
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Term
| Cells of the Immune System |
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Definition
| Lymphoid, Mononuclear phagocytes, Granulocytic, Dendritic |
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Term
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Definition
20-50% of white blood cells
T cells, B cells, and NK cells |
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Term
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Definition
Monocytes that circulate in the blood and
Macrophages found in tissues |
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Term
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Definition
Neutrophils
Eosinophils
Basophils
based on morphology and cytoplasmic staining characteristics |
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Term
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Definition
| Main function is the presentation of antigen to T cells |
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Term
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Definition
The generation of the cellular elements of blood, including:
Red blood cells (RBC)
White blood cells (WBC) or leukocytes
Platelets |
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Term
| types of hematopoietic cells |
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Definition
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Term
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Definition
A general term for a white blood cell
Lymphocytes, granulocytes and monocytes are all leukocytes |
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Term
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Definition
| A class of white blood cells that consist of small and large lymphocytes |
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Term
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Definition
(adaptive immunity cells)
B lymphocytes (B cells)
T lymphocytes (T cells) |
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Term
| Large granular lymphocytes |
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Definition
| Natural killer (NK) cells, lymphocytes of innate immunity |
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Term
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Definition
NK cells (large granular lymphocytes) are found throughout the tissues of the body but mainly in the circulation
Constitute 5-10% of lymphocytes in human blood
Contain cytotoxic substances which are important for protection against viruses and some tumors
Secrete cytokines which
Prevent viral replication and
Helps to activate T cell-mediated immunity |
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Term
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Definition
Effectors of innate immunity – specialized in the capture, engulfment and killing of microbes
Work in the anaerobic conditions found in damaged tissue
Are short-lived and die at site of the infection
Are phagocytic cells that contain toxic substances in intracellular granules
Employ oxygen-dependent and oxygen-independent pathways to destroy pathogens |
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Term
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Definition
Monocyte progenitors in the bone marrow differentiate into pro-monocytes, which enter the blood, where these differentiate into monocytes
Monocytes circulate in the blood for about 8 hours, then mature and migrate into tissues, they are then referred to as macrophages.
Differentiation of monocyte into macrophage requires changes
Monocyte cells enlarge 5-10 times
Increased intracellular organelles
Increased phagocytic ability
Production of hydrolytic enzymes
Secretion of soluble factors
There are tissue specific “fixed” macrophages and “free” macrophages |
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Term
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Definition
Dendritic cells are so called because of their many surface membrane folds, similar in appearance to dendrites of the nervous system
These folds allow maximum interaction with other cells of the immune system
There are three main kinds of dendritic cells which are found in skin and in T cell and B cell areas of lymphoid tissue:
Langerhans cells (LH)
Interdigitating cells (IDC)
Follicular dendritic cells (FDC)
Most dendritic cells
Possess high levels of surface MHC class II molecules
Process and present peptide antigens to T cells
Their role is to recognize microbial antigens through innate receptors and process and present them to T cells of the adaptive immune system
Follicular dendritic cells (FDC) hold intact antigens in specialized areas of lymphoid tissues |
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Term
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Definition
Eosinophils are granular leukocytes which stain with eosin (red)
They are present at low levels in the circulation (1-6% of blood leukocytes
Eosinophils have some phagocytic activity but are primarily responsible for extracellular killing of large parasites such as worms
They usually bind to an antibody-coated parasite and release the contents of their granules (degranulate) onto the parasite surface |
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Term
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Definition
Basophils are granulocytes which stain with basic dyes (blue) and are present in very low numbers in the circulation (<0.2% of the granular leukocytes)
Basophils and mast cells are very similar in morphology
Both contain and release large characteristic electron-dense granules in their cytoplasm during allergic reactions
Like all the granulocytes, basophils are produced from stem cells in the bone marrow |
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Term
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Definition
Megakaryocyte is a bone marrow cells responsible for the production of blood platelets when its cytoplasm becomes fragmented
These fragments are blood platelets
Megakaryocytes account for less than 1% of bone marrow cells but can be 10 to 15 times larger than a typical red blood cell
The nucleus of the megakaryocyte is very large and lobulated, which, under a light microscope, can give the false impression that there are several nuclei
Megakaryocyte function is determined by a large number of cytokines, including thrombopoietin
Thrombopoietin is a glycoprotein hormone produced mainly by the liver and kidney that regulates the production of platelets by the bone marrow |
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Term
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Definition
Erythrocytes bind to immune complexes composed of antigen and antibody and carry these complexes to the liver where these are cleared by Kupffer cells
Erythrocytes have an important immunological role in clearing immune complexes from the circulation in persistent infections and in some autoimmune diseases
Kupffer cells = phagocytic cells of the liver that line the hepatic sinusoids |
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Term
| Mononuclear Phagocyte System |
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Definition
Mononuclear phagocyte system
System of phagocytes located mainly in the organs and tissues
Monocytes are present in the blood stream and settle in the tissues as macrophages
Macrophage-like cells in the liver – Kupffer cells
Macrophage-like cells in the brain – Microglia |
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Term
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Definition
Several stages
Phagocyte attraction to the site of infection
Phagocyte contact with the microbe
Ingestion (endocytosis)
Killing of the ingested microbe by means of oxygen and oxygen-independent mechanisms |
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Term
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Definition
Way of making microbes more palatable to the phagocyte
Molecules coating a microbe, such as complement or antibody facilitate contact and ingestion of the microbe |
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Term
| Macrophages Respond to Pathogens |
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Definition
Bacterium (red) binds to cell-phagocytic receptors of the macrophage (blue)
Bacterium is engulfed into an endocytic vesicle called a phagosome
Fusion of the phagosome with lysosomes forms an acidic vesicle called a phagolysome
Contains toxic molecules and hydrolytic enzymes that kill the bacterium
Bacterial component binding to a signaling receptor sends a signal to the macrophage’s nucleus
This initiates the transcription of genes for inflammatory cytokines
The cytokines are synthesized and secreted into the extracellular space |
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Term
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Definition
Any molecule or molecular fragment that can be bound to by an antibody or be bound by an MHC molecule and presented to a T-cell.
Can be proteins, lipids, or sugars
Can be found on the surface or secreted by microorganisms |
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Term
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Definition
(immunoglobulins)- Proteins molecules synthesized by cells of immune system
That recognize antigens |
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Term
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Definition
Occasionally the infection outruns the innate immune response
Innate immunity has a restricted number of receptors to recognize pathogens
This activates the adaptive immune system
The adaptive immune system is mediated by lymphocytes
Which expand into effector cells and also persist as memory cells
The adaptive immune system generates a huge diversity of immunoglobulins (Ig) and T cell receptors
Upon infection, only the B cells with specific Ig, or T cells with specific receptors, are stimulated to proliferate and differentiate into effector cells |
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Term
| Organs of the Immune System |
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Definition
Distinguished by function
Primary and secondary lymphoid organs
Thymus and bone marrow are primary organs
Where maturation of lymphocytes takes place
Lymph nodes, spleen and mucosal-associated tissues are secondary organs
Which trap antigen and promote lymphocyte maturation |
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Term
| Lymphocytes and Lymphoid Tissues |
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Definition
Lymphocytes are
Found in lymphoid tissues
Activated in the secondary lymphoid tissues
Arise from stem cells in bone marrow
B cells - mature bone marrow
T cells - mature thymus
Primary lymphoid tissues
Bone marrow and thymus
Secondary lymphoid tissue and lymphatics
Spleen and lymph nodes |
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Term
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Definition
Site of T cell development and maturation
T cells in the thymus are called thymocytes
Thymus is a flat,bilobed organ situated above the heart
Function is to generate a diverse repertoire of T cells to protect the body from infections |
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Term
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Definition
Site of B-cell origin and development
B cells proliferate and differentiate by interacting with stromal cells and cytokines |
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Term
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Definition
Small lymphocytes travel in blood and lymph.
Antigens are carried to lymph nodes, as are lymphocytes, enabling interactions
When an antigen is encounter the lymphocyte will no longer recirculate. |
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Term
| Secondary Lymphoid Organs |
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Definition
Meeting place where lymphocytes circulating blood encounter antigens brought from sites of infection
Antigens derived from infections originating in connective tissues (as a result of skin wounds) are carried by the lymphatics to the nearest lymph node
Dendritic cells activated by infection also carry antigens |
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Term
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Definition
Lymphocytes leave blood and enter lymph nodes where they are activated by pathogens
Pathogens drain from site of infection (example: foot) to lymph nodes via afferent lymphatic vessels
Activated lymphocytes stay in lymph nodes and divide and differentiate into effector cells, while non-activated cells leave through efferent lymphatics
Lymphocytes recirculate at a rate of 5 X 106 cells/min |
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Term
| Architecture of the Lymph Node |
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Definition
Kidney-shaped; packed with lymphocytes & macrophages through which lymph percolates
Pathogens and dendritic cells carrying pathogens arrive in afferent lymph
Pathogens are degraded and used to stimulate lymphocytes
Lymphocytes arrive at lymph nodes in arterial blood; extravasate from capillaries
In lymph nodes, there are discrete sites where B cells and T cells congregate
Effector B cells; plasma cells -secrete antibodies
Lymph node increases in size due to dividing lymphocytes - “swollen glands”
Expansion occurs in lymphoid follicles
As lymphocyte development proceeds, follicle shape changes - germinal center |
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Term
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Definition
Filter for blood that removes old or damaged cells = Red pulp
Site where blood-borne pathogens encounter lymphocytes (a secondary lymphoid organ) = White pulp.
Blood is the only way in and out for lymphocytes as well as pathogens.
Spleenic macrophages and dendritic cells in the spleen to take-up antigen and stimulate T an B-cells.
White pulp of spleen consists of sheath of lymphocytes called the periarteriolar lymphoid sheath (PALS) surrounding a central arteriole (CA)
T cells are closest to the CA, while B cells are more peripheral, forming a B cell corona |
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Term
| Mucosal-Associated Lymphoid Tissue (MALT) |
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Definition
Mucosal surfaces lining digestive, respiratory and urogenital tracts are the major sites of entry for pathogens and are defended by MALT
Tissues range from loosely organized clusters of lymphoid cells to well-organized structures – tonsils, appendix
The gut associated lymphoid tissues, GALT include tonsils, adenoids, appendix and Peyer’s patches that line the gut
Bronchial-associated lymphoid tissues, BALT |
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Term
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Definition
Pathogens arrive through direct delivery across mucosa mediated by specialized cells called M cells
Lymphocytes enter from the blood, if not activated, leave in the lymphatics.
(cops waiting in house) |
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Term
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Definition
Lymphocytes that expand persist, providing long term memory
First time infection results in a primary response which leads to memory of the pathogen.
Subsequent infections with the same pathogen, having the same antigens, will elicit a secondary response which is much faster and stronger than the original primary immune response.
This is the basis of vaccination |
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Term
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Definition
Mutation in immune function genes leads to immunodeficiency -- different kinds….
In some, only one aspect of immune response is affected
In others, adaptive immunity is completely absent
Leading to devastating vulnerability to all infections
Extreme example of immunodeficiency due to disease is the acquired immune deficiency syndrome, AIDS
Caused by infection with the human immunodeficiency virus, HIV |
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