Lecture 2 Slides Tissues And Cells Of The Immune System Flashcards
(133 cards)
0
Q
When does maturation of B cells occur? What does it produce?
A
Occurs in the absence of antigens, in bone marrow, and produces antigencially committed B cells, each of which expresses antibody with a single antigenic specificity
1
Q
Clonal selection hypothesis
A
- Every individual contains numerous clonally derived lymphocytes, each clone having arisen from a single precursor and being capable of recognizing and responding to a distant antigenic determinant
- Antigen selects specific pre-existing clone and activates it
2
Q
When does Clonal selection occur
A
When an antigen binds to a B cell whose membrane bound antibody molecules are specific for epitopes on that antigen
3
Q
What happens during Clonal expansion
A
Clonal of an activated B cell leads to a clone of memory B cells and effector B cells, called plasma cells. All cells in the expanded clones are specific for the original antigen
4
Q
Plasma cells
A
Effector B cells
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Q
What do plasma cells secrete
A
Antibody reactive with the activating antigen
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Q
What does cloning of T cells result in
A
Memory T cells and effector T cells
7
Q
T-H cells are what kind cells? What do they secrete?
A
Effector at cells
Secrete cytokines, and cytotoxic T lymphocytes
8
Q
Primary or central lymphoid tissue
A
Bone marrow, thymus
9
Q
Secondary or peripheral lymphoid tissue
A
Lymph nodes, spleen, mucosa associated lymphoid tissue
10
Q
Where are lymphocytes generated
A
In the primary lymphoid organs
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Q
Where are adaptive immune responses initiates
A
In the secondary lymphoid organs
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Q
From where do all immune cells come from
A
Hematopoietic stem cell
13
Q
What do hematopoietic stem cells become
A
Multi potential stem cells
14
Q
What do multi potential stem cells become
A
Myeloid progenitor cells or lymphoid progenitor cells
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Q
What happens in bone marrow
A
Hematopoietic stem cell becomes common myeloid progenitor
16
Q
What does common myeloid progenitor become
A
One of four things
Immature Langerhans DC (epithelial tissue)
Immature interstitial DC (nonepithelial tissue)
Monocytes
Plasmacytoid DC precursor
17
Q
What do immature Langerhans and interstitial DC cells mature into
A
Langerhans DC (lymph node) Interstitial DC (lymph node, spleen)
18
Q
What do monocytes differentiate into
A
Macrophages and monocytes-derived DC
19
Q
What do T cells develop in the thymus
A
Self tolerance
20
Q
Where is the thymus gland
A
In the thorax in the anterior mediastinum
21
Q
How does thymus age
A
Enlarges during childhood but after puberty undergoes a process of involurion resulting in a reduction in the functioning mass of the gland. It continues to function throughout life, however.
22
Q
How is thymus arranged
A
It is arranged into an outer, more cellular, cortex and an inner, less cellular, medulla.
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Q
What happens to T cells in thymus
A
Immature lymphoid cells enter cortex, proliferate, mature and pass on to the medulla. From the medulla mature T lymphocytes enter the circulation.
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What cells are present in the thymus
Lymphoid cells
Epithelial cells
Macrophages
Other supporting cells
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What is different about epithelial cells in the thymus
They have different appearances in different locations within the gland. They form a sup-capsular layer and a network in the cortex and medulla. Deep in the medulla they are also aggregated into Hassall's corpuscles.
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What is structure of thymus? Where does it originate?
Bilobed
| Derived from endoderm of the third and fourth pharyngeal pouches
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Lymphatic system
The major lymphatic vessels and collection of lymph nodes
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Lymph nodes and their two main functions
Small bean shaped structures lying along the course of lymphatics
Phagocytic cells act as filters for particulate matter and microorganisms
Antigen is presented to the immune system
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General structure of lymph node
has cortex, para cortex and medulla. Has germinal centers in cortex.
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How does lymph leave the medulla
Efferent lymphatic
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Medullary cords
Antibody secreting plasma cells
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What does medulla consist of
Strings of macrophages and medullary cords
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How do naive lymphocytes enter lymph? Leave?
Enter from the bloodstream through specialized post-capillary venules.
Leave through the efferent lymphatic
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Spleen structure
Has a thin connective tissue capsule from which short septa extend inwards. These septa are in turn connected to a complex reticulum framework.
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Two distinct components of spleen
Red pulp and white pulp
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Red pulp
Consists of large numbers of sinuses and sinusoids filled with blood and is responsible for the filtration function of the spleen
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White pulp
Consists of aggregates of lymphoid tissue and is responsible for the immunological function of the spleen
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Which is largest secondary lymphoid organ?
| What is its specialty?
Spleen
| Traps blood borne antigens
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Where is spleen? What are its two main functions?
It is located in the upper left quadrant of the abdomen.
| It acts as part of the immune system and as a filter.
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Where is lymphoid tissue notably found outside of spleen and lymph nodes
GI tract, respiratory tract, urogenital tract
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Gut associated lymphoid tissue (GALT)
Comprises
Tonsils, adenoids (waldeyer's ring)
Peyer's patches
Lymphoid aggregates in the appendix and large intestine
Lymphoid tissue accumulating with age in the stomach
Small lymphoid aggregates in the esophagus
Diffusely distributed lymphoid cells and plasma cells in the lamina propria of the gut
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What do large aggregates of GALT have?
Distance B cell follicles and T cell areas. Antigen presenting accessory cells are also present.
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Peyer's patches
Large aggregates of lymphoid tissue found in the small intestine
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M cells
Epithelial cells with complex micro folds in their surfaces. In small intestine.
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Why are M cells important
Help transfer antigen from gut lumen to Peyer's patches
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Function of Peyer's patches
Facilitate generation of an immune system response within the mucosa. Antigens in these patches stimulate B cell precursors and memory cells.
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Cutaneous associated lymphoid tissues
Skin provides an important anatomical barrier to extreme environment
Cells of immune system exist within skin.
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How do antigen specific lymphocytes respond to soluble protein antigen in a lymph node
Effector and memory lymphocytes exit node via efferent lymphatic
Not known if they leave through vein
Migrate to site of antigen in tissue
Antibodies are secreted into circulation to eliminate antigen
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Most abundant blood cells
Red blood cells
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Least abundant blood cells
Basophils
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Lymphocytes
Two broad subtypes - B cells and T cells
| Are all derived from bone marrow. T cells mature in thymus. Mature lymphocytes all have a similar appearance.
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What is appearance of mature lymphocyte
Small cells with deep,basophilic nucleus and scanty cytoplasm
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Where do B and T cells circulate
In the blood and through body tissues
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Where do plasma cells come from? What do they secrete?
B cells. Secrete immunoglobulins
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How do T cells react to antigens
Some of them (CD4+) secrete lymphokines which act on other cells involved in the immune response. Others (CD8+, cytotoxic) are able to cause lysis of infected cells.
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B cell mechanism
B cell binds to antigen
B cells activate helper T cell, which release lymphokines
B cell Creates effector cell or plasma cell and secretes antibodies
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Types of T cells
Resting and activated helper T cells
Resting cytotoxic T cell
Activated killer cell
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Types of cytokines
Lymphokines/secreted by mature helper T cell
| Monotones/secreted by macrophages
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How does killer cell work
Approaches target cell, engulfs it and releases target oriented granules
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MALT
Mucosal associated lymphoid tissue
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What does MALT include
Bronchus assoc. Lymphoid tissue BALT
Gut assoc. Lym tissue GALT
Naso-pharyngeal lump. Tissue NALT
URL-genital associated lymp. Tissue
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How do lymphocytes respond to presented antigens
Antibodies and lymphokines
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What are lymphocytes responsible for?
Control adaptive Immune response by secondary action on participating cells
Kill virally infected host cells
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Immunogenicity
The ability of a molecule or molecular configuration to induce an immune response
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Antigen
A molecule able to react with ensuing antibody or T cell receptors
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Haptens
Antigens that lack immunogenicity
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Functional T cell subsets
Gamma delta T and alpha beta T
Alpha beta T splits into CD4 and CD8
CD4 splits into TH1 and TH2
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T lymphocyte phenotypic markers
Cd4, CD8, CD45RO, CD45RA, CD3, TCR, CD2, CD28, CD5, Cd7(human only), Thy-1 (mouse only)
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CD2 function and location
Adhesion molecule; signal transduction
| TH and TC
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CD3
Signal transduction element of T cell receptor
| TH
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CD4
```
Adhesion molecule that binds to class II MHC molecules; signal transduction
TH
```
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CD5
Unknown
| TC
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CD8
Adhesion molecule that bind to class I MHC molecules ;signal transduction
Usually TC
Variable NK
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Cd16 (FcgammaRIII)
Low affinity receptor for F. Region of IgG
| In NK
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CD21 (CR2)
Receptor for complement (C3d) and Epstein Barr virus
| B cell
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CD28
Receptor for costimulatory B7 molecule on antigen- presenting cells
TH and TC
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Cd32(FcgammaRII)
Receptor for Fc region of IgG
| B cell
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Cd35(CR1)
Receptor for complement (C3b)
| b cell
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CD40
Signal transduction
| B cell
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Cd45
Signal transduction
| B, TH, TC, NK
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CD56
Adhesion molecule
| NK cells
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Macrophages and dendritic cells are derived from? Functions
Bone marrow
Phagocytosis
Secretion of cytokines
Antigen presentation
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Mononuclear phagocytic system
All cells that perform phagocytosis, secretion of cytokines, and antigen presentation
Macrophages and dendritic cells
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Polymorphs and mast cells are involved in
Effector side of immune response
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Brain phagocytes
Microglial cells
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Lung phagocytes
Alveolar macrophages
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Liver phago.
Kupffer cells
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Kidney phago
Mesangial phagocytes
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Lymph node phago
Resident and recirculating macrophages
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Spleen phago
Macrophages
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Blood phago
Monocytes
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Joint phago
Synovial A cells
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Mononuclear phagocyte system
Blood monocytes, phagocytes resident in tissues or fixed in the endothelial layer of blood capillaries
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Wandering macrophages
Alveolar and serosal macrophages
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Brain microglia
Cells which enter the brain around time of birth and differentiate into fixed cells
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Factors secreted by activated macrophages
IL-1, IL-6, TNF-alpha, complement proteins, hydrolytic enzymes, interferon alpha, tumor necrosis factor, GM-CSF, G-CSF, M-CSF
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Interleukin 1
Promotes inflammatory response and fever
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Interleukin 6 and TNF alpha
Promote innate immunity and elimination of pathogens
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Complement proteins
Promote inflammatory response and elimination of pathogens
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Hydrolytic enzymes
Promote inflammatory response
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Interferon alpha (INF-alpha)
Activates cellular genes, resulting in the production of proteins that confer an antiviral state on the cell
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Tumor necrosis factor (TNF-alpha)
Kills tumor cells
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GM-CSF, G-CSF, M-CSF
Promote inducible hematopoiesis
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Granulocytes cells 3
Neutrophils
Eosinophils
Basophils
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What do neutrophils respond to
Chemo tactic signals
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How do neutrophils leave capillaries
A complex process, involving marination, rolling and then attaching, following which they emigrate between the endothelial cells
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Margination
Flowing nearer to the endothelial lining of blood vessels
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Extravasation, diapedesis
Emigrate between endothelial cells
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What mediators are involved in activating neutrophils
Microorganism secreted substances
IL-1, released by macrophages
Histamine, from basophils, tissue mast cells, blood platelets
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Histamine causes
Capillar and venular dilation
111
C3a and C5a
Chemo tactic for phagocytic cells
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Acute phase proteins like C-reactive protein
Produced by liver
Can attach to C-polysaccharide component of cell wall of bacteria and fungi. Activates complement system, making C3a form, coat organism, facilitating phagocytosis
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Purpose of eosinophil
Give large parasites such as helminthology a hard time
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How do eosinophils work
Attach via C3b receptors. Release various substances from their granules. Including major basic protein (MBP), plus cationic proteins, per oxidase, arylsulphatase B, phospho lipase D, and histaminase. Contents of granule damage parasite membrane.
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Basophil
Non-phagocytic cells that, when activates, release numerous compounds from the basophilic granules within their cytoplasm
116
In what do basophils play a major role
In allergic responses, particularly type I hypersensitive reactions
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Want do granulocytic cells do
Mediate anti microbial and cytotoxic activity of macrophages and neutrophils
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What intermediates depend on oxygen
Reactive oxygen and nitrogen intermediates
119
Reactive oxygen intermediates
Superoxide anion, hydroxyl radicals, hydrogen peroxide, hypochlorite anion
120
Reactive intermediates
Nitric oxide
Nitrogen dioxide
Nitrous acid
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Oxygen independent intermediaries
Defensins
TNF alpha
Lysozyme
Hydrolytic enzymes
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From where do dendritic cells arise
Both myeloid and lymphoid lineages
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Ehich myeloid pathway gives way to DCs
Monocytes/macrophage pathway
124
Which dendritic cells arise directly from myeloid progenitor
Langerhans and interstitial dendritic cells
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Which DCs arise from monocytes
Myeloid dendritic cells
126
Are follicular dendritic cells derived from bone marrow
No
127
Two types of programmed cell death
Necrosis
| Apoptosis
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Necrosis process
```
Chromatin clumping
Swollen organelles
Flocculent mito
Disintegrate
Release intracellular contents
Inflammation
```
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Apoptosis process
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Mild convolution
Chromatin compaction and segregation
Condensation of cytoplasm
Nuclear fragmentation
Blebbing
Apoptopic bodies
Phagocytosis
```
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Human pluripotent stem cells
Can differentiate into a variety of cell types
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Maturation of mononuclear macrophage
Bone marrow - stem cell to monoblast
Blood - monocytes to macrophage
Tissue - macrophage activated
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Maturation of lymphocytes
Develop in generative lymphoid organs
| Immune responses to foreign antigens occur in peripheral lymphoid tissues
