Lecture 4 - Immunology Overview Flashcards
What is Innate Immunity
Does not require specific recognition of each pathogen. It works the same no matter what the problem is and works the same no matter how many times it has encountered the problem but it is FAST
Name 5 innate defenses of the body
- Continually replenishing outside barrier (epithelium)
- Water ‘flush’ (tears, saliva, etc.)
- Secreted anti-microbial molecules
- Competitive flora of ‘friendly’ microbes (normal flora)
- Muco-epithelial escalator
Is the innate system always on?
Yes, The innate immune system is always on and therefore very fast
What causes the heat and redness seen in inflammation?
The release of histamine from sentinel cells (mast cells) increases the local capillary flow by relaxing pre-capillary sphincters. This explains both head and redness
After histamine is released from mast cells, 3 actions occur to initiate the inflammatory response. What are they?
- Increase the local capillary flow by relaxing pre-capillary sphincters (heat and redness)
- Cause the capillary endothelial cells to gap, causing blood fluid and any soluble molecules it contains to flood into the affected tissues (swelling = edema)
- Cause the capillary endothelial cells to show ‘stop signs’ that cause certain inflammatory response cells to exit capillaries and move to the site of the injury.
What cells are recruited to the site of the injury upon exit from the capillary that work to clear foreign materials and dead cells
Phagocytic cells, PMNs and Macrophages
What different molecules are recruited in Acute vs Chronic inflammation
Acute: Plasma proteins, Mast cells, Neutrophils
Chronic: Cell Proteins, Lymphocytes, Macrophages
Name the three response organs listed in diagram for inflammation
Brain, Liver, Bone Marrow
What is the main response molecule produced during inflammation?
Histamine
What is acquired immunity or adaptive immunity?
A specific defense system that uses specific lymphocytes (B and T) that are selected during infection because they recognize (bind specifically) a particular microbe, but are useless against most other microbes (do not bind)
What are the other two terms for acquired immunity
Specific immunity, Adaptive immunity
The lymphoid system altogether has a mass greater than what organ?
Brain
What are the two primary lymphoid tissues
Thymus, Bone marrow
What occurs in the primary lymphoid tissues
Sites of lymphocyte development and ‘education’ (B cells in bone marrow and T cells in thymus)
Name the 6 secondary lymphoid tissues listed in notes
Lymph nodes, spleen, adenoids, tonsils, Peyer’s Patches and Appendix
What is a secondary lymphoid tissue
Organized tissues with large numbers of lymphocytes and antigen-presenting cells
Why are there a large number of cells in secondary lymphoid tissue?
Increases the odds that lymphocytes will find ‘their’ antigen (Ag). Think singles bar where Ag, Ag-presenting cells, and lymphocytes must slowly move past one another, which maximize their interactions.
What is the site of lymphocyte development?
Primary lymphoid tissue
Another name for BCR protein
Antibody
What is the role of the antibody
It binds to the problem, both ‘coating’ and ‘flagging’ it for destruction
Do T Cells produce and release antibodies?
No, Their specific protein receptor is not secreted. Their receptor (TCR) remains stuck to the surface of the T cell, only binding to process protein presented to them on the surface of other cells.
What occurs once a TCR binds to a process Ag on another cell?
The T cell releases one or more proteins, termed cytokines, which act on other host cells.
What do cytokines do?
Can signal the destruction of infected host cells, activation and division of host cells, modify vasculature and neural functions, change whole body temperature, etc.
How are antigens found in the body?
As molecules, cells, or even whole tissues
Can BCR and TCR bind the entire antigen?
They can only bind a very small part of any antigen
What is the epitope?
The small region of the antigen that actually binds to a B or T cell antigen recognition receptor
What is an Antigen
Any molecule ‘seen’ by either of two highly specific receptor proteins;
- immunoglobulins on or secreted by B-Lymphocytes
- TCR proteins on T-Lymphocytes
What is an HLA ‘presenter’ protein?
Pieces or protein antigens also bind less specifically to these that are then shown to any T cell that wanders by and can decide if anything needs to be done.
Streptococcus pneumoniae is what type of bacteria?
Gram + that can cause pneumonia, usually in weakened individuals
How does S. pneumoniae cause a serious infection and inflammatory response?
It enters the blood, crosses the blood-brain barrier, and infects the meninges. This meningitis is highly fatal!
T or F, A decreasing percentage of S. pneumoniae strains are resistant to common antibiotics
False, An increasing percentage
Does S. pneumoniae posses an outer capsule?
Yes, the capsule blocks phagocytosis by PMNs and macrophages.
What is immunogenic for bacterial capsules?
It means that it is a polysaccharide that induces an adaptive immune response
How are phagocytes able to pickup and engulf pathogens?
Only when antibodies coat the outer layer of bacteria. The antibodies act as ‘suitcase handles’ that help the phagocytes pickup and engulf these slippery pathogens
What is opsonization?
The process of coating antigens with antibodies to enhance phagocytosis
What are Fc receptors?
The cell surface receptors that are pre-existent on the surface of all phagocytes. They bind to the antibodies.
T or F, Cytokines are usually required for a full and effective adaptive immune response
True
Is the CHO capsule a virulence factor/
Yes, it is a major virulence factor as it protects the bacterium from innate phagocytic activity
How do we protect ourselves against bacterium with a CHO-capsule?
Because it is protected from our innate phagocytic activity, we need the adaptive immune response to help protect us. B-cells with the ‘correct’ immunoglobulin receptor on their surface will find the bacteria by its CHO-capsule
After the the B cell has recognized and internalized the bacteria and chops it up, What is the next stage?
Some of the bacterial protein is presented on HLA to a T cell with the correct TCR. The T-lymphocyte then release cytokines that activate other nearby cells. It also causes itself and the B cell to divide into a large clone of identical daughter lymphocytic cells.
When is the antibody secreted during the response?
After the T cells and B cells begin to divide after
