Introduction To Immunology Flashcards
You are studying microbes and discover that a particular microbe replicates intracellulary and uses host-cell energy resources. What type of microbe have you discovered?
Intracellular microbe
What are some examples of infectious organisms?
Worms
Protozoans
Fungi
Bacteria
Viruses
What is immunity?
A set of cooperative defense mechanisms which provide protection from various infectious diseases.
What are antigens (noninfectious foreign substances) capable of doing?
Eliciting an immune response.
What are Ags?
Substances (microbial or nonmicrobial, proteins, carbohydrates, lipids and nuclei acids) that induce an immune response.
What is an antibody?
A protein produced by the immune system when it detects antigens.
What is an epitope?
A portion of an Ag molecule to which the antibody binds.
What are the smallest epitopes to which an antibody can be made?
3 - 6 amino acids
5 - 6 sugar residues.
True or false: all immunogens are Ags, but not all Ags are immunogens.
True
What are immunogens?
Ags which can stimulate an immune response
All large molecules have multiple ____
Epitopes
What do Abs bind to?
Conformational antigenic epitopes.
True or false: all large molecules have one epitope.
Fales; all large molecules have multiple epitopes.
You are exposed to a new antigen. What line of defense will initially be used in order to fight against infection?
Innate immunity
You have been exposed to an antigen for the second time. How will the response of innate immunity differ from its initial response?
It will not change.
What type of barriers are important to innate immunity?
Physical and chemical barriers.
What are the three principal components of innate immunity?
Physical and chemical barriers
Phagocytic cells
Blood proteins (complement system and other mediators).
You are studying the response of the body to a particular antigen. You note that the antigen is eventually engulfed by a particular molecule. What molecule is this?
Phagocytes.
This is innate immunity.
What are antimicrobial peptides?
Small peptides which target pathogenic microorganisms ranging from viruses to parasites.
What is complement?
A system of plasma proteins that enhances the ability of Abs and phagocytic cells to clear pathogens from an organism.
What are acute phase proteins?
A large group of blood proteins whose plasma concentrations change in response to tissue inury, acute infections, buns or inflammation.
What are cytokines?
Signaling molecules that aid cell to cell communication in immune responses.
What are chemokines?
A subfamily of cytokines secreted by immune cells to induce chemotaxis in nearby cells.
What are phagocytes?
Immune cells that have the ability to ingest and digest microbes.
What are two cells that are components of adaptive immunity?
B and T lymphocytes.
What is the specificity of innate immunity?
Innate immunity is specific for molecules shared by groups of related microbes and molecules produced by damaged host cells.
What is the specificity of adaptive immunity?
For microbrial and nonmicrobial antigens.
How does the diversity of innate and adaptive immunity compare?
Innate immunity has a limited diversity and adaptive immunity has a large immunity.
What type of immunity has memory?
Adaptive immunity
True or false: innate and adaptive immunity mechanisms are reactive to self.
False
Phagocytes, dendritic cells and NK cells are part of innate immunity. How long does it take for them to develop?
Hours
B lymphocytes, T lymphocytes, antibodies and effector T cells are part of adaptive immunity. How long does it take for these components to develop?
Days
True or false: many cells and molecules of the innate immune system are also used by the adaptive immune system and vice versa
True
In addition to inflammation, the innate immune system is responsible for what other function?
It evaluates the invader in the context of intracellular vs extracellular microbes and provides instructions to adaptive immunity.
How do cells communicate?
Through direct cell-to-cell contacts, as well as interactions involving cytokines and chemokines.
What are two main functions of cytokines?
Regulate growth and differentation of all immune cells
Activate the Effector functions of lymphocytes and phagocytes.
Each cytokine acts via a ____ expressed on target cells.
Specific signaling receptor
What are chemokines?
A large subset of structurally related cytokines that regulate cell migration and movement.
What is the primary function of phaogocytes?
To ingest and destroy microbes and get rid of damaged tissue
What are the two primary phagocytes?
Neutrophils and macrophages
What are the steps in functional responses of phagocytes?
Recruitment of cells to sites of infection
Recognition of and activation by microbes
Ingestion of the microbes by the process of phagocytosis
Destruction of ingested microbes.
What molecule to activated phagocytes secrete?
Cytokines. They promote or regulate immune responses.
What is a primary function of neutrophils?
They mediate the earlies phases of inflammatory reactions.
What is the most abundant population of circulating spherical white blood cells?
Neutrophils
Where are neutrophils produced?
In the bone marrow.
They are stimulated by G-CSF.
They circulate in the blood for hours or a few days. They only function of 1 - 2 days and then die.
When a patient is exposed to something they are allergic to, what cells act to protect against reactions that cause allergic diseaes?
Mast cells, basophils and eosinophils
Mast cells, basophils and eosinophils share what common feature?
They have cytoplasmic granules filled with various inflammatory and antimicrobial mediators.
In what region of the body are mast cells most likely to be found?
Sites of the body that are exposed to the external environment, such as the skin.
They are found in close proximity to blood vessels in order to regulate vascular permeability and effector cell recruitment.
How do mast cells modulate the behavior of neighboring cells?
Through the relase of mediators.
What is the mononuclear phagocyte system?
A system that includes circulating monocytes and resident tissue macrophages. They play roles in innate and adaptive immunity.
Dependingon the organ, they may have specialized phenotypes.
Where do cells of the mononuclear phagocyte system arise from?
Committed precursor cells in the bone marrow, drivven by M-CSF.
What occurs to monocytes during inflammation?
They enter the blood circulation and tissues where they further mature into macrophages.
What are some functions of macrophages?
Clearance of cellular debris
Tissue immune surveillance
Response to infection
Resolution of inflammation
Dendritic cells are associated with what type of immunity?
Innate immunity
What is the function of the dendrites on dendritic cells?
They stimulate T cells to induce adaptive immunity.
What are the two divisions of dendritic cells?
Myeloid and plasmacytoid cells.
What are mDCs?
Myeloid dendritic cells. They are derived from monocytes and differentated from peripheral blood mononuclear cells.
Interactions between what three cells are critical to the development of specific immunity?
T and B cells
T cells and antigen presenting cells (APCs)
What is the humoral theory of immunity?
The host defense against infections is mediated by substances present in body fluids (humors).
What do immune cells secrete?
Receptors (Ags) which recognize microbrial toxins and combat invading microbes.
How is humoral adaptive immunity mediated?
By Abs in the blood and mucosal secretions which are produced by B lymphocytes.
Abs recognize microbial antigens, neutralize microbes and target them for elimination.
What is CMI (cell mediated imminuty) controlled by?
Responses of T cells, which often function in concert with Ag-presenting cells and phagocytes to eliminate microbes.
What does CMI mediate?
Host defense against intracelluar microbes, such as viruses and some bacteria, where they are inaccessible to circulating Abs.
What is the function of CMI?
The killing of infected cells to eliminate reservoirs of infection.
In humoral immunity, what do B lymphocytes sercrete that prevent infections and eliminate extracellular microbes?
Abs
In cell mediated immunity, what to T helper cells activate to kill phagocytized microbes?
Macrophages
What is the function of specificity?
It ensures that the immune response to a microbe is selective to that microbe.
What is the function of diversity?
Enables the immune system to respond to a large variety of Ags
What is the function of memory?
It increases the ability to combat repeat infections by the same microbe
What is the function of clonal expansion?
It increases the number of Ag-specific lymphocytes to keep pace with microbes.
What is specialization?
It generates responses that are optimal for defense against different types of microbes.
What is the function of contraction and homeostasis?
Allows the immune system to recover from one response so that it can effectively respond to newly encountered Ags.
What is the function of nonreactivity to self?
It prevents injury to the host during responses to foreign Ags.
What does the clonal selection hypothesis attempt to answer?
How the immune system responds to large numbers of different Ags.
According to this hypothesis, Ag-specific clones of lymphocytes develop before and independent of exposure to Ag.
What is a clone (clonal selection hypothesis)?
A lymphocyte of one specificity and its progeny.
What is the clonal selection hypothesis?
A hypothesis that states that the immune system generates a large number of clones during the maturation of lymphocytes, thus maximizing the potential for recognizing diverse microbes.
During clonal selection, what is the role of each Ag?
It selects a pre-existing clone of specific B cells and stimulates the proliferation and differentation of that clone.
What are the steps of clonal selection?
- Lymphocyte clones mature in generative lymphoid organs in the absence of antigens.
- Clones of mature lymphocytes specific for diverse antigens enter lymphoid tissues.
- Antigen-specific clones are activated “selected” by antigens.
- Antigen-specific immune responses occur.
When Ag is introduced into an individual, lymphocytes with receptors for this Ag ….
Seek out an bind Ag and are triggered to proliferate and differentiate, giving rise to clones of cells specific for the Ag.
In clonal selection, the cells from the clones or their products specifically react with …
The Ag to neutralize or eliminate Ag.
What are some Ag-specific cells in clonal selection responsible for?
The memory involved in adaptive immunity.
What are the phasese of adaptive immune responses?
Antigen recognition
Lymphocyte activation
Antigen elimination
Contraction
Memory
Are memory cells or naive lymphocytes more effective in combating microbes?
Memory cells
During immunologic memory, what happens to expanded lymphocyte clones?
They die in a contraction phase and homeostasis is restored.
What is an important goal of vaccination?
The generation of memory responses.
What is a difference between primary and secondary antigen responses?
The secondary response to Ag X is more rapid and larger than the primary response.
After each immunization, what happens to the levels to Abs?
They decline.
What is active immunity?
Immunity conferred by a host response toa. Microbe or microbial Ags
What is passive immunity?
Immunity conferred by adoptive transfer of antibodies or T lymphocytes specific for the microbe.
What is a similarity between active and passive immunity?
Both provide resistance to infection and are specific for microbial Ags.
Does active or passive immunity generate immunologic memory?
Active immune responses.
What do B lymphocytes develop into?
Ab secreting cells
What do T helper lymphocytes secrete?
Cytokines
What is the function of cytotoxis T lymphocytes?
They recognize Ags on infected cells and kill these cells.
What is the function of regulatory T cells?
They suppress and prevent immune responses (e.g. To self antigens).
How do extracellular microbes survive?
They grow extracellulary.
