Chapter 8 - The Immune System Flashcards
What is an innate or nonspecific immunity?
The rapid nonspecific part of the immune system that attacks pathogens first line.
What is the adaptive immune system?
It is a part of the immune system which issues a later response but more specific to pathogens
In general, What are the molecules involved in the innate immune response?
Antimicrobial molecules, phagocytes such as macrophages, dendritic cells, monocytes, and neutrophils, and cytokines
In general, what are the molecules involved in the adaptive immune response?
B cells, T cells, antibodies
Where are all the immune cells produced (including B cells and T cells)?
In the bone marrow
What is the function of the thymus?
It is a small gland in front of the pericardial sac (for the heart) and is where the T cells mature.
B cells are already mature when they leave the bone marrow, but they are stored and activated in an organ called the _________.
Spleen
What is the function of lymph nodes?
Located in the neck, it is a site of immune cell communication to plan an attack, so there is a high concentration of B and T lymphocytes. They also filter the blood for pathogens.
The spleen has several different functions such as…
Storage for WBCs and platelets, a recycling center for old RBCs, and a filter for blood and lymph of the immune system
What is the name of the cell that gives rise to both white blood cells, red blood cells, and platelets?
Hematopoietic stem cells
B cells mature in the ________ while T cells mature in the ________.
Bone marrow, thymus
B & T cells, originatefrom what type of WBC?
Lymphocytes (agranulocytes)
What is the most common white blood cell granulocyte?
Neutrophils
Neumonic to remember granulocytes
NEB:
Neutrophils
Eosinophils
Basophils
What is the function of basophils?
Basophils are known for releasing histamine in response to allergic reactions.
What is the function of eosinophils?
They recruit/respond to parasitic invasion by releasing granules containing peroxidase enzymes. These enzymes digest tissue and destroy parasites along the way.
What is the function of neutrophils?
The most common WBC recruited as the innate immune response.
They are recruited to inflammation sites by chemotaxis and their main function is to phagocytize (ingest) microorganisms to destroy them.
Adaptive/specific immune response can be subdivided into two types. What are they?
Humoral immunity which is driven by B cells and antibodies.
Cell mediated immunity which is driven by T cells.
What are the three types of lymphocytes?
Natural killer (NK) cells, T cells, and B cells
Platelets originate from cells called _______.
Megakaryocytes
How does the gastrointestinal tract play a role in the nonspecific innate immune response?
The stomach secretes acid which destroys many pathogens. The gut contains a lot of beneficial bacteria that keep out the bad bacteria.
What are interferons?
They are proteins (produced by cells infected by viruses) which prevent viral replication and dispersion in nearby cells.
What are mast cells?
A type of granulocyte mostly related to basophils and are involved in the first line innate immune response. They release large amounts of histamine responding to severe allergic reactions.
What is pus made out of?
A collection of dead neutrophils
How does the “complement system” generate a nonspecific immune response?
The complement system uses a number of proteins in the bloodstream which target bacteria no specifically and punch holes in the bacterial cell walls to make them osmotically unstable.
Which class of MHC molecules are involved in the endogenous pathway?
MHC-I
What are the cells which are considered professional antigen-presenting cells?
Macrophages, dendritic cells, some B-cells, and certain epithelial cells
What are dendritic cells?
They are WBCs which have the ability to phagocytize pathogens and present the pathogenic antigens on their cell surface through MHC molecules. They can differentiate from monocytes or their own cell line. They are abundant in the skin.
What is the function of natural killer (NK) cells?
These are a type of lymphocyte involved in the nonspecific innate immune response. They are able to detect the down-regulation of MHC molecules (caused by some viruses) and induce apoptosis in virally infected cells.
What types of things occur during an inflammatory response?
- Release of histamine and prostaglandins
- Increased blood flow to injury site
- Increased permeability of veins and lymph vessels
- Increased interstitial fluid and solutes to the tissues causing swelling and pain
MHC Class I proteins are present in ________.
most nucleated cells
What is the purpose of MHC class I proteins?
It allows leukocytes to distinguish between healthy cells and infected cells. A healthy cells will present its own self-antigens using MHC class I proteins on its surface. However, an infected cell (maybe by a virus) will present the viral antigens using MHC class I proteins on its cell surface.
MHC Class II proteins are found on _________.
Professional antigen presenting cells such as dendritic cells, macrophages, and some B cells.
What is the main purpose of MHC Class II proteins?
These protein complexes allow immune cells (WBCs) to communicate with each other and activate a number of immune responses (both innate and adaptive).
Give an example of a MHC Class II molecule being used in the exogenous pathway
When a macrophage engulfs a bacterial cell, it uses MHC Class II proteins to present the bacterial antigens on its cell surface. Then, the macrophage can release chemicals which recruit helper T cells & B cells.
What are the two types of adaptive immune responses?
Humoral immunity and cell-mediated (cytotoxic) immunity
Where are antibodies located?
They can be present on the surface of cells or can float freely in the blood, air, lymphatic fluid
What is the mechanism of action for antibodies when encountering/binding an antigen?
- Opsonization - recruit other leukocytes to phagocytize those antigens
- Agglutination - cause the pathogens to clump together to form insoluble complexes that can be phagoctized
- Neutralization - block the ability of pathogens to invade tissues
What is the valuable region of an antibody?
It is the regions at the tips of the Y shaped antibody which are antigen binding sites.
True or false:
There are only 1 type of antibody that is used for all types of pathogens.
False, there are five different isotypes of antibodies (IgM, IgD, IgG, IgE, and IgA). They are utilized depending on the pathogen type and location of recruitment in the body.
True or false:
Each B cell makes only one type of antibody.
True
What is the clonal selection hypothesis of B cells?
Hypothesis which states that an individual B cell expresses receptors specific to 1 distinct antigen, determined before the antibody ever encounters the antigen. In other words, the antibody’s fate is predetermined & random before being exposed to a certain pathogen’s antigens.
True or false:
Antibody creation is a random process. The number of antibodies created coupled with a semiflexible binding requirement, ensures that a foreign antigen will be bound by a host antibody.
True. Exposure to an antigen is not a requirement for antibodies to be created. The antibody is created ahead of time in the body and when exposed to the specific pathogen antigen, it proliferates and creates more of those antibodies and memory B cells.
What is humoral immunity?
“Antibody mediated immunity”, when an antibody binds a specific antigen receptor causing B cells to undergo differentiation into plasma cells and memory B cells
What are plasma B cells?
They are a type of B cell that is “activated” upon exposure/binding to a specific antigen. It produces many free antibodies.
What are memory B cells?
They are activated B cells which differentiated from the original B cell that bound the antigen. Their purpose is to travel to and stay in lymph nodes in the body and await reexposure to the same antigen.
What happens when a memory B cell is exposed to the same pathogen a second time?
The memory B cells will rapidly proliferate and differentiate into plasma cells to produce more antibodies specific to that pathogen.
Which cells are responsible for the secondary immune response?
Memory B cells
What constitutes cell mediated (cytotoxic) immunity?
The maturation and activation of T cells
What are the three types of T cells?
Helper T-cells (CD4+ T cells), killer cytotoxic cells (CD8+ T cells), and suppressor T-cells
CD4+ T cells (helper T cells) respond to MHC Class I or II molecules? Why?
MHC Class II; because they use these proteins to communicate and recruit other immune cells.
CD4+ T cells are most effective against what kinds of infections?
Bacterial, fungal, parasitic infections (since they deal with exogenous antigens only)
CD8+ (Cytotoxic cells) respond to antigens on MHC Class I or II molecules?
MHC Class I molecules because they deal with endogenous antigens
Cytotoxic T cells are most effective against what types of infections?
Mostly viral infections and intracellular bacterial or parasitic infections
How do cytotoxic T cells carry out their function?
They directly kill virally infected cells by injecting toxic chemicals that promote apoptosis in the cell.
T cells under go maturation in the thymus. There are two types called positive & negative selection. What is the difference?
Positive selection allows only for maturation of T cells that can respond to antigens on MHC.
Negative selection allows for apoptosis to occur in T cells that are self-reactive to eliminate them.
What happens to T cells when infected with HIV?
HIV causes the loss of helper T cells, preventing the immune system from mounting an adequate response to any infections
What is the function of suppressor/regulatory T cells?
They express a protein called Foxp3 & they help to tone down the immune response once infection has been adequately contained & turn off self reactive lymphocytes (both B cells and T cells)
What are self-antigens and what is the purpose of them?
Antigen proteins present on the surface of every cell that makes up the body’s tissues. They signal to immune cells that the cell isn’t foreign and shouldn’t be attacked.
What is a common therapy for auto immune diseases?
Injection of glucocorticoids which have immunosuppressive qualities
What is the lymphatic system?
It is a type of circulatory system made of one way vessels that carry lymphatic fluid which drain into the thoracic duct and right lymphatic duct in the posterior chest.
What are lymph nodes?
Small bean shaped structures along lymphatic vessels which provide a space for immune cells to be exposed to pathogens (by antigen presenting cells) and proliferate
If a cell is infected by a virus, what kind of lymphocyte would you expect to respond during a secondary immune response?
Cytotoxic T cell
What is active immunity?
This is when the person is exposed to the pathogen (which can be through a vaccine or naturally) and their immune system is stimulated to produce antibodies against that pathogen
What is passive immunity?
This is the transfer of antibodies from one individual to another (like in a placenta to fetus transfer of antibodies)
What is the function of the lymphatic system?
It maintains fluid homeostasis by preventing fluid from building up inside of the tissues and returning that fluid back to the bloodstream
What can happen if the blood has a low concentration of albumin proteins? How does the body mediate this?
Low concentration of albumin causes oncotic pressure to decrease which causes less blood to be drawn into the venules. This causes blood to pool in the capillaries and stay in the tissues.
To mediate this lymphatic vessels take up this remaining blood and circulate it back into the bloodstream
Veins and lymph vessels are similar because they both contain _____________.
One way valve systems
What are some examples of innate immunity in the body?
Secretion of mucus in the nose which traps bacteria, stomach acid, cough reflex, skin, respiratory airways, eyes, blood-brain barrier
