The Immune Response Flashcards
What are the two types of immunity?
humoral and cellular
What is humoral immunity, and what specific cell is associated with it?
refers to the synthesis and release of antibody into the blood and other body tissues, where it is capable of direct combination with and neutralization of antigen; B-cells
What is cellular immunity, and what specific cell is associated with it?
refers to the production of sensitized lymphocytes (T-cells) and their products (lymphokines), which play a role in the rejection of skin transplants, defense against infectious organisms, tumor immunity, and delayed-type hypersensitivity reactions
What is the parent cell of both B- and T-cells?
stem cells from bone marrow
In which organ do T-cells differentiate?
thymus
Where do B-cells differentiate?
fetal liver, bone marrow, or gut-associated lymphoid tissue (GALT)
What, in man, is considered to be the equivalent of the Bursa of Fabricius in birds?
bone marrow
What are T-cells considered to be once they are exposed to antigen?
activated
What kind of cell do B-cells become and what do they secrete?
plasma cells; antibody
What is the appearance of a plasma cell?
large, off-center nucleus, gradated blue cytoplasm (dark edges, lighter center)
In terms of B- and T-cells, what does CD stand for, and what is it?
cluster of differentiation; membrane protein found on all white cells
What is the purpose of the constant recirculation of B- and T-cells throughout the body?
increases contact with foreign antigens, as there are only a small number of lymphocytes that recognize any one antigen
What are null cells?
also called “natural killer” cells; a small percentage of lymphocytes (5-15%) that do not express the markers of either T- or B-cells; they do not have any unique surface antigens, but they do have specific antigen combinations that can be used for identification
What CD numbers can be found on null cells, and which ones do they lack?
possess CD16, CD56, and CD95; lack CD3, CD4, and CD8
Where are null cells found?
mainly found in the spleen and peripheral blood
What are null cells capable of?
mediate cytolytic reactions and kill target cells without prior exposure to them; can recognize and destroy any foreign cells without regard to MHC restrictions
Null cells represent the first line of defense against what other kinds of cells?
virally infected cells and tumor cells
What is the suspected relationship between null cells and cytotoxic lymphocytes?
if foreign cells escape the action of cytotoxic lymphocytes, null cells may take over the destruction of these foreign cells
What is the predominant type of lymphocyte in the peripheral blood, and in what percentage do they occur?
T-cells; 60-80%
What is the average half-life of T-cells?
2.2 years
What is meant by cloning in immunological terms?
once a T-cell becomes activated, it travels to the lymph nodes and spleen where copies of the T-cell are made and proliferated; further cloning will take place once these original clones colonize other lymphoid tissue
Besides the spleen and lymph nodes, what are the other three locations considered to be secondary organs?
appendix, Peyer’s patches in the intestines, and mucosal-associated lymphoid tissue (MALT) in the GI, respiratory, and urogenital tracts
What happens if antigen contact occurs in the lymph nodes?
lymphocyte traffic halts for ~24 hrs. in an attempt to immobilize antigen, which causes the lymph nodes to become enlarged (lymphadenopathy)
What are T-effector cells?
also known as T-cytotoxic cells, or killer cells (NOT null cells); T-cells with the CD8 marker that react against foreign tissues, viruses, and tumors, and have the ability to destroy target cells
What are T-helper cells?
also known as T-inducer cells; T-cells with the CD4 marker that produce lymphokines, which assist B-cells in the production of antibody, as well as assist T-effector cells; also play a role in controlling the entire immune system
What percentage of T-cells are actually T-helper cells?
40-60%
What are T-regulatory cells?
formerly known as T-suppressor cells; also have the CD4 marker; produce lymphokines that suppress antibody production and cellular response
How do T-regulatory cells relate to autoimmune disease?
they play an important role in suppressing immune response to self-antigen
What are lymphokines?
cytokines produced primarily by lymphocytes; small polypeptides, given off by antigen-stimulated T-cells, that regulate the functions of other cells and tissues, such as growth, secretion, and differentiation
What is the life-span of B-cells?
3 days
Where are B-cells committed to forming antibodies to specific antigens or antigen groups?
bone marrow
What are memory cells?
type of long-lived B-cell formed after an intial antigen encounter that can be quickly activated upon a second exposure to the same antigen
Which virus is known to selectively invade B-cells?
Epstein-Barr virus (EBV)
What is rosette formation?
phenomenon exhibited when sheep red cells are mixed with T-cells, in which the red cells attach to CD2 receptors, forming a daisy-like pattern; because all T-cells express the CD2 marker, this technique can be used to identify T-cells in the laboratory
What are the two most common methods for identifying T- and B-cells in the lab, and what do both methods rely on?
fluorescence microscopy and flow cytometry (most often used); the use of labeled monoclonal antibody against specific surface antigens
What are the three fluorescent tags that can be used for T- and B-cell identification?
rhodamine, fluorescein, and phycoerythrin
What is flow cytometry?
automated system based on the scattering of light as cells flow in single file through a laser beam
What does the amount of forward light scatter measure in flow cytometry?
size
What does the amount of side light scatter measure in flow cytometry?
granularity
How do fluorescent-tagged antibodies identify the subgroups of T-cells?
each antibody has a fluorescent tag of a specific wavelength; the percentage of cells exhibiting fluorescence of a certain wavelength is determined and the ID is made
How long after an initial antigen encounter can IgM antibody be found in the serum?
3-4 days
What is the activity of IgM in the primary immune response?
quickly peaks and plateaus, and the decreases over the next few weeks
How long after exposure does the presence of IgG occur?
1-2 weeks
How does the activity of IgG compare to the activity of IgM in the primary immune response?
rises to higher levels, peaks within a few weeks, and decreases over the course of a few months
When is a secondary (anamnestic) response induced?
upon second and subsequent exposure to the same antigen
IgM occurs in the secondary response in the same fashion as the primary, but what is different about the occurrence of IgG?
reaches much higher levels and decreases very gradually, often over a period of several years
What is the major benefit of memory cells?
provide long-lived protection against disease caused by the antigen it was originally formed for
Are T-cells capable of memory?
yes
What is the immune response (Ir) gene?
structural gene in the MHC that exerts a regulatory role on the immune response
What is the Instructive/Template Theory of antibody synthesis?
antigen in some way directs the cells to form its corresponding antibody by serving as a mold or template and altering protein synthesis so that antibody with a specific fit is made
What is Ehrlich’s Side Chain Theory?
cells contain specific surface receptors for antigen which are selected and turned on by contact of antigen with the cell; antibody is then produced by the receptors breaking off and circulating as antibody
What is the Clonal Selection Theory?
each lymphocyte has the genetic information available to make one particular antibody, and molecules of the antibody are built into the cell surface membrane as receptors; antigen will then combine with the lymphocytes carrying antibody that is a good fit; these original lymphocytes will then be stimulated to divide or form clones of cells synthesizing antibody with the same specificity as that of the parent cell
Which theory is the basis for the most presently accepted hypothesis of the mechanism of antibody formation?
Clonal Selection Theory
What characterizes an immunodeficiency disease?
individual is deficient in B-cells, T-cells, phagocytic cells, and/or complement system
What is congenital hypogammaglobulinemia (agammaglobulinemia)?
abnormal delay in synthesis of normal antibody by newborns, resulting in susceptibility to infection; patients usually recover by age 9-15 mos., and the condition is not normally threatening due to the probable protection offered by maternal IgG
What is acquired agammaglobulinemia?
side effect of infection, malignancy, autoimmune disease, malnutrition, burns, or sometimes unknown sources; susceptibility to infection results, and testing will show a decrease in IgG and plasma cells
What are immunoproliferative diseases?
diseases in which there is a malignant proliferation of one of the key cells of the immune system
What is hypergammaglobulinemia?
increased gamma globulins
What is a monoclonal gammopathy?
the overproduction of immunoglobulins or their fragments by a single clone of plasma cells; multiple myeloma, Waldenstrom’s macroglobulinemia, and heavy chain disease all fall under this category
Define multiple myeloma.
consists of plasma cell tumors in the bone marrow that overproduce a single class of immunoglobulin (50-60% of cases are IgG); in about 20% of cases, Bence-Jones proteins will be found in the urine; survival time is around 2-5 years
What are Bence-Jones proteins?
abnormal proteins that will coagulate upon heating to 45-55*C, then redissolve upon boiling
Describe Waldenstrom’s macroglobulinemia.
involves IgM overproduction; bone lesions can be seen, though rarely; survival time is 3-5 years for high risk patients, and ~12 years for low risk patients
What is heavy chain disease?
condition in which the serum contains high amounts of incomplete heavy chain fragments; can be IgG, IgM, or IgA in nature
What is polyclonal gammopathy?
a generalized response to an antigen by a variety of cells arising from different clones; often seen in patients with chronic infections, hepatic disease, collagen diseases, and autoimmune diseases
What is monoclonal antibody?
synthesized antibody used for diagnostic testing; created by fusing a plasma cell with a myeloma (cancerous plasma cell) that can be grown indefinitely in the laboratory
Can monoclonal antibodies be used for treating patients?
no; they are cancerous in nature, and so can only be used for testing purposes
What is a plasmacytoma?
plasma cell tumor
