A cell produced by the bone marrow which, when stimulated by an
antigen*, becomes either a memory
cell or a plasma cell that forms antibodies against that antigen. Compare
T lymphocyte.
T lymphocyte (T cell)
Definition:
A type of cell produced by the thymus that plays a major role in immune
reactions. See also B
lymphocyte.
A cell found floating freely in the amnion sac (a membranous sac containing
the amniotic fluid) surrounding an embryo.
astrocyte (astroglia)
Definition:
A star-shaped cell of the nervous system which provides nutrients,
support and insulation for neurons.
bacteriocyte
Definition:
A modified fat
cell found in certain insects which contain groups of rod-shaped objects
thought to be symbioticbacteria.
cystocyte
Definition:
The insect equivalent of a platelet
(a blood cell which helps bring about blood clots). At a site of injury,
these cells will break down into threads around which plasma can gel, stopping
the flow of hemolymph
(the arthropod equivalent of blood) from the site.
A red blood cell; erythrocytes carry oxygen in the blood via hemoglobin.
erythrocyte ghost
Definition:
A red blood cell
that has had its contents removed and replaced with drugs and other bioactive
chemicals to be delivered to target cells.
A type of delivery system.
A class of leukocytes
characterized by the presence of granules in their cytoplasm.
These cells are active in allergic immune
reactions such as arthritic inflammation and rashes. This class includes
basophils, eosinophils
and neutrophils.
helper T lymphocyte (helper T cell)
Definition:
A type of white
blood cell produced by the thymus gland whose presence is necessary
for normal levels of antibodies
to be produced by B
lymphocytes, both in the body (in
vivo) and in experimental situations (in
vitro).
hemocyte
Definition:
A hemocyte is a blood cell. The term tends to refer to the blood cells
found in invertebrate animals.
hepatocyte
Definition:
The major liver tissue cell.
human leukocyte-associated antigens (HLA antigens)
Proteins on the
outer part of body cells that help fight illness. These proteins vary from
person to person. Scientists think that people with certain types of HLA
antigens are more
likely to develop insulin-dependent
diabetes. The HLA
antigens are also responsible for histocompatibility
reactions.
immunocyte
Definition:
A leukocyte
that is able to stage an immune response.
A pale, nucleated cell that acts as a part of the immune system by
destroying invading cells and removing debris. See also granulocyte,
lymphocyte, macrophage
and monocyte.
A type of non-granular leukocyte
that mainly stays in lymphatic tissue (e.g., the lymph nodes) and is active
in immune responses, including the production of antibodies.
macrophage (histiocyte)
Definition:
A type of large leukocyte
that travels in the blood but can leave the bloodstream and enter tissue;
like other leukocytes, it protects the body by digesting debris and foreign
cells.
megakaryocyte
Definition:
A huge cell in the bone marrow that produces blood platelets.
melanocyte
Definition:
A type of cell
which is found in the epidermis
of the skin and which produces the pigment melanin.
Melanocytes are transparent cells with dendrites.
monocyte
Definition:
A type of large, round leukocyte
that engulfs and breaks down debris and invading cells. Monocytes are formed
in bone marrow and have round or kidney-shaped nuclei.
myelocyte
Definition:
A motile cell produced by and found in the bone marrow which develops
into granular leukocytes.
oocyte
Definition:
A developing female reproductive cell
which divides by meiosis
into four haploid
cells, forming one ovum
that goes on to potentially become fertilized by a sperm
cell and two to three polar bodies that subsequently degenerate.
A particle found in the bloodstream that binds to fibrinogen
at the site of a wound to begin the blood clotting process. Platelets are
formed in bone marrow, where they arise from cells called megakaryocytes.
An oocyte which
was originally formed while the female was an embryo
and which is suspended in prophase
I of the first meiotic
division until the female reaches sexual maturity. Then, it grows and
divides into the secondary
oocyte and a polar body, ending the first meiotic division. The primary
oocyte is a diploidcell.
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