The Immune System &
Essential Terms
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- Acute: Having a sudden and severe onset.
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- Agglutination: The aggregation or clumping together
of cells within the blood as a result of their interaction with
specific antibodies called agglutinins.
Agglutinins: a specific kind of antibody whose
interaction with antigens is manifested as agglutination.
Anemia: reduced level of oxygen carrying
pigment hemoglobin in the blood due to lack of red blood cells,
which occurs when the rate of hemolysis exceeds the rate of red
cell production in the bone marrow.
Antibody, aka
Immunoglobulin: a protein
essential to the immune system that is produced by B lymphocytes
in response to the presence of an antigen. Antibodies bind to
the specific antigens that stimulated their production, commencing
the crucial process of neutralization and destruction of the
antigen. Antibodies can be produced artificially by immunization.
Antigen: any substance that stimulates the
production of antibodies to counteract that substance and combat
infection and disease. Many antigens are foreign proteins not
naturally found in the body, including bacteria, microorganisms,
toxins, viruses, etc.
Antigen-Antibody
Reaction: the essential
immune response of the body, in which B cells recognize an antigen
and stimulate antibody production.
- Antigen-Antibody Reactions
occur when unique areas on the surface of the antigen molecules
fit precisely into appropriate concave combining sites on the
surface of the antibody molecules to form antigen-antibody complexes,
which renders antigens harmless, agglutinizes antigens to allow
phagocytes to digest large numbers of antigens at a time, or
activates the complement system.
- Antigen-Antibody Reactions
normally produce immunity, but they can also be responsible for
autoimmunity.
Antigen Determinant:
small area on the surface
of an antigen molecule that fits a combining site of an antibody
molecule and binds the antigen and antibody in the formation
of an antigen-antibody complex.
Antinuclear Antibody
(ANA): an autoantibody
that reacts with the body's own nuclear material and is found
in the blood serum of patients with autoimmune disorders.
Autoantibody:
an antibody that reacts
against a normal component in the body.
Autoimmune Disease: An alteration of the immune system
that results in the body reacting against its own cells and tissues
due to antigens normally present in the internal cells stimulating
development of antibodies which are unable to distinguish antigens
of the internal cells from external antigens, setting off reactions
that cause a variety of diseases.
Autoantigen:
an internal body component
that stimulates the production of autoantibodies and results
in an autoimmune reaction against tissues of the body.
Autoimmunity: an abnormal condition in which
the immune system develops antibodies against the body's own
tissues, causing a reaction that results in an autoimmune disease.
Theories of autoimmunity include:
- Forbidden Clone Theory:
a theory that at birth all cells that might react against the
body have been eliminated, leaving only cells that will react
against foreign substances; when cells that react against the
body persist after birth, they can be activated by something
and result in an autoimmune disease.
- Sequestered Antigen Theory:
a theory that immunological tolerance depends on the relationship
between immunologic cells, body cells, and antigen exposure.
The theory postulates that antigens sequestered in the body are
isolated from circulation and don't contact the immune system.
If body tissues are damaged the sudden exposure of these antigens
is not recognized by the immune system and an autoimmune reaction
results.
Bilirubinemia: the accumulation of bilirubin
in the blood and the tissues of the skin.
Bilirubinuria: the presence of bilirubin in
the urine.
Complement: a complex enzymatic serum protein
that functions to produce lysis or phagocytosis.
Complement cascade: biochemical process involving
complement components in which their interaction with each other
may result in or make antigens more susceptible to lysis or phagocytosis.
Cytokine: a compound produced by certain
cells that acts as a messenger to control the actions of lymphocytes
and other cells in an immune response.
Direct Antiglobulin
Test, aka DAT, aka Coomb's Test: A test for the presence of antibodies that coat
and damage red blood cells. Used to diagnose autoimmune hemolytic
anemia in the absence of agglutination or to find which antibody
class is responsible for the destruction.
DIC : Disseminated
Intravascular Coagulation:
aggregation of platelets and clotting within small blood vessels,
sometimes using coagulation factors faster than they can be produced
in the liver, which can result in severe bleeding.
Erythrocyte: the red blood cell, its principle
function being the transportation of oxygen.
Hematocrit: aka
PCV (Packed Cell Volume): a
measure of the packed cell volume of the blood expressed as a
percentage of the total blood volume.
Hemoglobinuria: an abnormal presence in the urine
of hemoglobin that is unattached to red blood cells.
Hemoglobinemia: an abnormal presence in the blood
of hemoglobin that is unattached to the red blood cells.
Hemolysis: the breakdown of red blood cells
and the release of hemoglobin into the blood plasma.
Hemolytic Anemia: disorder characterized by the
premature destruction of red blood cells with anemia resulting
when the production of red blood cells by the bone marrow is
outpaced by the premature destruction.
Idiopathic: without a known cause.
Immune Response:
the body's defensive
reaction that produces antibodies to destroy invading antigens.
Components are antibodies, lymphocytes, phagocytes, complement
and other complement activators, and inhibitory proteins that
give healthy cells protection against foreign particles.
- Antigens interaction with
the reticuloendothelial system's cells trigger Humoral Immune
Responses, involving B lymphocytes and B cells and the production
of antibodies to react with antigens, and Cell-Mediated Immune
Responses, involving T lymphocytes and T cells and the mobilization
of macrophages upon antigenic stimulation.
- Humoral and Cell-Mediated
Immune Responses are interdependent with Humoral influencing
T cells and Cell-Mediated influencing the function of B cells.
Immune system: A biochemical system that functions
to respond to invading antigens by producing antibodies or sensitized
leukocytes that will recognize and destroy those antigens. First
line defenses are local barriers like skin, mucous membranes
and inflammation. When local barriers fail or are inadequate
to protect the body, humoral and cell mediated responses develop.
The principal organs of the immune system include the bone marrow,
the thymus, and lymphoid tissues, as well as the lymph nodes,
the spleen and the lymphatic vessels. Autoimmune disorders arise
when the immune system wages its functions against the body's
own cells and tissues.
Immunoglobulin,
aka Antibody: any of
five structurally and antigenically distinct humoral antibodies
present in serum and secretions. In response to specific antigens,
immunoglobulins are formed in the bone marrow, spleen and lymphoid
tissues. Types of immunoglobulins pertaining to AIHA include
IgG and IgM.
- IgG: specialized protein
synthesized by the body in response to invasions by the bacteria,
fungi and viruses; protects against red cell and white cell antigens;
contains two parts, one to bind to the antigen, one to other
cells of the immune system, phagocytes, which then engulf the
foreign protein that the antigen is bound to.
- IgM: the first immunoglobulin
produced in response to antigens and is found in circulating
fluids. It triggers the increase production of immunogloblin
G and the complement fixation required for effective antibody
response.
Interferon: a protein that induces the production
of a protective protein in healthy cells.
Interleukin-2:
a protein with various
immunologic functions, including the ability to initiate proliferation
of activated T cells.
Killer Cell:
a lymphocyte that lacks
the surface markers of the B & T cells, but has the ability
to attack targets directly upon antibody stimulation.: represent
a small proportion of the lymphocyte population.
Kilogram: equivalent to 2.2 pounds.
Leukocytes: white blood cells which are the
main components of the body's immune system and help protect
against disease and infection; function to phagocytize bacteria,
fungi and viruses, detoxify toxic proteins and develop immunities.
There are several kinds of Leukocytes: lymphocytes, produced
in the lymph nodes, spleen, thymus, and the bone marrow: monocytes,
produced mostly in the spleen and the bone marrow: and neutrophils,
produced in the bone marrow.
- Lymphocyte: occur as either
B Cells or T Cells, which play major roles in mounting the immune
response.
- B Cells compose about
10% of circulating lymphocytes and primarily mediate the Humoral
Immune Response. B Cells function to search out, identify and
bind with antigens. B Cells circulate in an immature form and
are antigenically stimulated to enlarge and undergo cell division,
transforming into cells called plasma cells or memory cells.
- Plasma cells synthesize
and secrete massive amounts of tailor made antibodies (immunoglobulins)
that attach to the antigen, thereby starting the process that
leads to destruction. This protective effect of immunoglobulins
is often referred to as the Humoral Immune Response.
- Memory cells do not secrete
antibodies at this time, but retain a memory of the antigen so
it can be dealt with more rapidly when next encountered. If reexposed
to the specific antigen that stimulated their production, memory
cells develop into antibody secreting plasma cells. It is this
memory function that is stimulated by vaccines.
- T Cells compose about
80% of circulating lymphocytes and primarily mediate the Cell-Mediated
Immune Response. T Cells are "educated" by the thymus
gland to fulfill a particular function. T cells are antigenically
stimulated to proliferate with antigen receptors on their surface
membranes. T Cells can be either T "helper" cells,
which assist in the production of antibodies by B cells, or T
"suppressor" cells, which suppress B cell activities
and help prevent the immune system from attacking its own tissue.
Though T Cells do not produce antibodies, T cells are also referred
to as "killer cells", since after attaching themselves
to the antigen covered cells, they secrete lymphokines and immunologically
essential chemical compounds, which activate macrophages that
destroy antigens.
- Monocyte: a leukocyte
that is phagocytic, which means that they engulf and eat up invading
bacteria and small particles.
- Neutrophil: a circulating
white blood cell essential for phagocytosis in which bacteria,
cellular debris and other particles are removed and destroyed.
Lymphokine: a chemical produced by T Cells
that attracts macrophages to antigenic cells and prepares for
attack.
Macrophage: a phagocytic cell of the reticuloendothelial
system.
Necrosis: localized tissue death that occurs
in groups of cells in response to disease, injury, or lack of
oxygen.
Phagocyte: a type of white blood cell that
is able to surround, engulf, and digest microorganisms and cellular
debris.
- fixed phagocytes don't
circulate and include the fixed macrophages and cells of the
reticuloendothelial system.
- free phagocytes circulate
in the bloodstream and include leukocytes and the free macrophages.
Phagocytosis: the process of certain cells engulfing
and digesting microorganisms and cellular debris.
Portal Vein: a large blood vessel that carries
blood from the stomach, intestines and spleen to the liver.
Pulmonary Embolism:
obstruction of the
pulmonary artery, which leads from the heart to the lungs, or
one of its branches in the lungs, by a blood clot, causing life
threatening conditions or sudden death.
Receptor: a chemical structure on the surface
of a cell that combines with an antigen to produce an immune
response.
Reticulocyte: an immature red blood cell characterized
by meshlike pattern of threads and particles.
Reticuloendothelial
System: the system
of the body including the macrophages, certain liver cells, the
bone marrow, spleen and lymph nodes; functions to defend against
infection and disposal of the products of the breakdown of cells.
Rouleaux: an aggregation of red cells in
what looks like a stack of coins or checkers.
Schistocyte:
a cell fragment from
an erythrocyte, found with hemolysis or intravascular coagulation.
Spherocyte: an abnormally shaped, damaged red
blood cell.
Thromboembolism:
a condition in which
a blood vessel is blocked by a clot.
Titer Test: a blood test that measures the
concentration of vaccination antibodies in the blood, thereby
accessing the need for another vaccination.
