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60 Cards in this Set

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  • Back
Define antigen.
something that the immune system can recognize--doesn't mean that it has to be foreign or pathological

Antigens can be self or foreign
Describe the function of primary lymphoid tissues and name those in the body.
microenvironments in which development of lymphocytes can occur--where uncommitted cells become lymphocytes and where they learn to become the kind of lymphocytes that are needed

Bone marrow
Fetal liver and spleen

If one of the other sites is damaged in adult, spleen can become site of hematopoeisis
Describe the function of secondary lymphoid tissue. Name the ones in the body.
regional sites to encourage interactions b/w antigen, APC, and antigen responsive cells so that the immune response can be activated and coordatinated

lymph nodes
peyer's patches
tonsils and adenoids
What are tertiary lymphoid tissues?
Tissues that can form at sites where aggressive immune responses are happening
Where are the responses for the innate immune system encoded? What is the fxn of innate immune system?
Responses are encoded in DNA/germ line

Recognizes microbial structures that are common to many members of a group of pathogens but not found among human cells
Many molecules in the innate immune system recognize...?
Pathogen Associated Molecule Patterns -- PAMPs

Substance that many bacteria can release (ie endotoxin)
Where are the responses for the adaptive immune system encoded?
Uses rearrangement of gene segments that happen SOMATICALLY to generate antigen binding molecules that are highly specific for the antigens that are able to recognize

gene recombination
What are toll-like receptors? Which part of the immune system are they a part of?
Molecules that recognize many of the molecular patterns that pathogens have; important activators of immune system

Innate immune system
How is the adaptive immune system different from the innate immune system in terms of how many molecular structures it can recognize?
The innate can recognize a wide variety of structures.. (PAMPs is a key example).. this is why innate can respond quickly

Adaptive with B and T cells has a unique receptor on its surface that recognizes only one molecule structure -- response doesnt occur until 4 or 6 days after antigen enters body
What does it mean when we say adaptive immunity confers memory?
biologically means that there are differentiated B and T cells that have expanded and proliferated and are specific for an antigen. They have very long lives

These memory cells when encounter Ag again, they're activated quickly
How are human and bacterial genomes different?
Mammalian cells methylate their DNA, where as bacterial cells do no.
What is hematopoiesis?
the process of producing all of the cells that constitute the immune system plus the RBC population

It's dependent on the presence of hematopoietic stem cells, which are self-renewing
What do lymphoid cells give rise to?
NK cells
T cells
B cells
Dendritic cell (only one kind)
What do myeloid cells give rise to?
majority of dendritic cells
Granulocyte cells
Phagocytic cells
-- monocytes, macrophages, neutrophils, eosinophils
Mast Cells
Erythroid progenitors
What do mast cells bind and what do they release?
Mast cells bind IgE Ab and release molecules like histamine and leukotrienes that are mediators of the allergic rxn
Where does hematopoiesis happen?
yolk sac -> fetal liver -> fetal spleen ->bone marrow

Originally occurs in all bones, but as an adult only occurs in flat bones, ribs, sternum, pelvis, vertebra
What makes the stem cell change from self-renewing cell to become a lymphoid progenitor and then to a B/T cell progenitor?
Controlled almost entirely by signals that the cell has receptors for that somehow sense the need for particular cells
What do the following signals do:
GATA-1: erythroid lineage
PU.1: erythroid
Ikaros: lymphoid devo
Oct-2: making B cells
What antigen is only present on the hematopoietic stem cells?
In addition to bone marrow, where else would you find stem cells?
Found circulating in the blood
What does necrosis mean? Describe the process.
Necrosis = deadness

Process by which the cell falls apart - cell lyses and organellar structures exit the cell. When DNA exits the cell, it makes a gell. When not in the correct environment with the correct proteins, DNA binds a lot of water and forms a gel.
What does apoptosis mean? Describe the process.
Apoptosis - falling out or falling away

Gets rid of cells in a tidy and deliberate way.

Bcl-2 is epxressed which prevents apoptosis. When a signal turns off or down-regulates the function of bcl-2 the cell goes through program where it compartmentalizes itself to be phagocytized in bites so that the internal contents of the cell never gets released

Phophotidylserine flips from the internal membrane to the external membrane to act as a signal for phagocytes.
What is the importance of Fas?
Fas controls the killing of cells that have inappropriate receptors and is important in downregulating the number of cells after things have expanded

Mutations in Fas results in lots of cells surviving that should normally die
Where are the following Igs found

A - saliva, tears, and sercreted in fluids at the epithelial/mucosal surfaces

E - activates mast cells and basophils, which work with defense against parasites

G - distributed thought all of the extracellular fluids of the body

M - naieve B cell only makes IgM
What do monoclonal Abs recognize that define different cell lineages?
CD (cluster of differentiation) antigens
Where are the following CDs found

3 - part of the receptor on T cells

4 - helper T cells
8 - cytotoxic T cells
35 - receptor for complement proteins and is on B cells but not on T cells or NK cells
How are granulocytes differentiated?
Based on the kind of granules that they have and other surface molecules that they carry
Describe neutrophils and their fxn.
Nucleus has 4-8 lobes

Leave the blood and go into tissues looking for infection; contains granules that are involved in eating particles the neutrophil ingested

Most common WBC, represent 40% in normal person
Describe eosinophils and their fxn.
Nucleus is 2-3 lobules

Useful in killing parasitic organisms

cytokine IL-5 is produced by the same kind of T cells that promote allergy responses; this cytokine also governs the cell's growth, increasing their production and making them live longer in tissues
Describe basophils and their function.
Host defence against parasites
What is a mastocytoma?
Mast cells malignantly transformed and interferes with bone formation

indication is bone fractures due to person not having enough calcium in their bones due to demineralization
What lineage to most dendritic cells come from?
Describe the dendritic cells that come from lymphoid lineage.
Cells make IL-4 and IL-5, which can help make a T cell become a helper T cell to promote antiparasitic activity or allergy responses
Describe the formation of B cells in the bone marrow.
Bony cavity is lined with epithelial called endostium. It makes special growth factors important for hematopoietic stem cells. Stem cells located under endostium. As they differentiate,they move towards the middle of the marrow cavity. While moving, they enounter the right signals to help them differentiate. As they move, they undergo gene rearrangements that lead to making a functional Ab. There are specific cytokines that retain cells and need to be turned off for cells to leave bone marrow and enter circulation

Early part of T cell committment occurs in bone marrow
What is the role of fat in the bone marrow?
Fat can be metabolized to make space in the marrow when hematopoiesis needs to be increased. Also a good source of fat soluble vitamins for the rapidly proliferating cells
How do T cells recognize the infected cell?
Bind to a structure on the cell that is a hybrid structure of a self membrane protein (MHC) and piece of pathogen

This gives rise to the term MHC restriction of T cell recognition
Describe MHC1 molecules.
CD8 cytotoxic T cells recognize MHC class 1 molecules

Has 3 domains (alpha 1-3) joined together with 4th domain called beta-2 microglobulin; between alpha1 and alpha 2 chains is a cleft for the protein antigen; a self protein is placed in the cleft in there's no pathogenic peptide

If there is a microbial peptide, there's a new structure that's made on the alpha helices. This plus the peptide fragement activates the T cell receptor
Describe MHC2 molecules.
have 4 domains, but are made of 2 separate chains
Where does CD8 bind to?
It binds to the alpha3 domain on the MHC1 molecule, enhacing the interaction between the T cell receptor and MHC1

CD8 ensures that this kind of T cell only interacts with MHC class 1 cells not class
At what age is T cell production at its maximum?
Age 10
Describe T cell maturation.
Cell moves through cortex and medulla and encounters stromal cells with MHC molecules on their surface. If they dont interact well, they don't get positive growth factors and they die. This is POSITIVE SELECTION which happens in the CORTEX

As the cell moves to the medulla, it undergoes a second selection. There are medullary epithelial cells that express an autoimmune regulator gene called AIRE that makes these cells able to express a lot of self peptides in small amounts. If any T cell interacts and becomes activated by these peptides, they are induced to die. This is NEGATIVE SELECTION IN THE MEDULLA

If aire is defective.. have autoimmune syndrome
What is Hassal's corpuscle?
at the junction of the cortex and medulla in the thymus... debris from thymocytes that have undergone apoptosis
What are high endothelial venules?
blood system that brings oxygen and takes waste away and also brings neive cells from circulation into tissue.

HEVs are post capillary venules that are highly cuboidal

They are very efficient at extracting naieve lymphcytes from circulation
What percentage of lymphocytes are extracted by the HEVs?
Over 80% exit the blood and enter the tissue
How is the separation of B and T cells in the lymph node maintained?
Chemokines that are produced in different areas. Chemokines are small cytokines that cause cells to move toward the chemokines.
What happens when a dendritic cell comes in through the afferent lymph and enters the tissue and activated the innate immune response?
When a B cell or T cell encounters the antigen, it changes it chemokine receptor patter that the T cell loses its focus to stay in the T cell region and moves towards the B cells or vice versa. They interact in a junctional zone b/w the 2 areas so the T cell can provide help to the B cell.

The B cell then re-expresses its chemokine receptor and goes back to its area. The B cell goes through a germinal center reaction where it proliferates heavily and becomes a mature Ab producing cell, then becomes a plasma cell or a memory B cell.
How is the spleen different from lymph nodes?
Spleen doesn't have afferent and efferent lymphatics. It only gets antigens that circulate in the blood.
Where are peyer's patches located? What are their role?
They are in the intestines. They are designed to pick up antigens directly from the lumen because there's a special cell called M cell on the surface overlying the Peyer's Patch.
Where are M cells found and what are their functions?
Peyer's patches

M cell transports particles from the lumen of intestines into the Peyer's Patch area. They can swallow bacteria and deliver them to the zone beneath the M cell where they can interact with a dendritic cell and a macrophage and can be chewed up and presented to T cells like in the other lymphoid organs.
Where are palatine tonsils?
located on the side of the tonsillar pillars in the back of the throat.
Where are lingual tonsils located?
located on the back of the tongue past the taste buds
Where are the adenoid or pharyngeal tonsils located?
back of the pharynx behind the uvula and behind where the air breathed in goes
What is the dendritic cell population called in the skin?
Langerhan cells
What MHC class is expressed on Langerhan cells?
MHC 2 since langerhan cells are dendritic cells
What happens if a keratinocyte becomes infected?
If keratinocytes get infected with a virus, the MHC 1 molecule will begin epxressing the viral-derived proteins which passes on signals to Langerhan cells
What is the molecule that keeps keratinocytes in contact with langerhan cells?
What happens when a langerhan cell gets activated?
E-cadherin molecules gets broken down. The LC will be upregulating a chemokine receptor on surface called CCR-7.

CCR-7 recognizes a chemokine that is produced in the lining of these afferent lymphatic vesicles which begin just below the basement membrane. There's a gradient of this chemokine which attracts cells that have the CCR-7

The LCs eneter the lymphatics and they are carried toward lymph nodes
Describe the flow of lymphatics in the lymph node.
Afferent lymphatics bring APCs charged with an antigen into the tissue and empties into the subscapular sinus. If a free antigen comes through the lymph, the sinus will trap it and prevent it from entering the lymph node.

Properly activated cells will migrate to the medulla of the lymph node where they are gathered and exit via the efferent lymphatics and head to the thoracic duct and into the left subclavian vein.
Where do plasma cells go to produce their Abs?
bone marrow because the growth factor environment is very favorable here
The spleen has white and red pulp. Describe each area.
White pulp - B/T cell zone

Red pulp - old RBCs are destroyed here; fibroblasts and stromal cells make a lot of growth factors that create a favorable environment for plasma cell proliferation