Untitled - D Ank Unlimited

differentiation antigen 228 Dimsdale, Dr. Thomas (1712–1800)
differentiation antigen
Epitope that appears at various stages of development or in
separate tissues. This cell surface antigenic determinant is
present only on cells of a particular lineage and at a particular
developmental stage; it may serve as an immunologic
marker. An antigen of protein or carbohydrate composition
that is linked only to a particular developmental stage.
The inappropriate presence of a differentiation antigen in a
tumor cell can render it a tumor-associated antigen.
differentiation factors
Substances that facilitate maturation of cells, such as the ability
of interleukin-2 (IL2) to promote the growth of T cells.
diffusion coefficient
Mathematical representation of the diffusion rate of a protein
in gel. The diffusion coefficient is useful in determining
antigen molecular weight. It is the ratio of diffusion rate
to concentration gradient.
DiGeorge syndrome.
DiGeorge syndrome
A T cell immunodeficiency involving failure of T cell development
but normal maturation of stem cells and B lymphocytes.
This deficiency is attributable to failure in the development of
the thymus, depriving the individual of the mechanism for T
lymphocyte development. DiGeorge syndrome is a recessive
genetic immunodeficiency characterized by failure of the
thymic epithelium to develop. Maldevelopment of the thymus
gland is associated with thymic hypoplasia. Anatomical
structures derived from the third and fourth pharyngeal
pouches during embryogenesis fail to develop, leading to
defects in the functions of both the thymus and parathyroid
glands. DiGeorge syndrome is believed to be a consequence
of intrauterine malfunction. It is not familial. Tetany and
hypocalcemia, both characteristics of hypoparathyroidism, are
observed in DiGeorge syndrome, in addition to the defects in T
cell immunity. Peripheral lymphoid tissues exhibit a deficiency
of lymphocytes in thymic-dependent areas. By contrast, the
B- or bursa equivalent-dependent areas such as lymphoid
follicles show normal numbers of B lymphocytes and plasma
cells. Serum immunoglobulin levels are within normal limits,
and the immune response is normal following immunization
with commonly employed immunogens. A defect in delayedtype
hypersensitivity is demonstrated by the failure of affected
patients to develop positive skin tests to commonly employed
antigens such as candidin or streptokinase and the inability
to develop an allograft response. Defective cell-mediated
immunity may increase susceptibility to opportunistic infections
and render a blood transfusion recipient vulnerable to a
graft-vs.-host reaction. There is also minimal or absent in vitro
responsiveness to T cell antigens or mitogens. The most significant
advance has been the identification of microdeletions
on human chromosome 22q11 in most DiGeorge syndrome
patients. Considerable treatment success has been achieved
with fetal thymic transplants and passive administration of
thymic humoral factors.
dilution end point
A value expressed as the titer that reflects the lowest
amount of an antibody giving a reaction. It is determined by
serial dilution of the antibody in serum or other body fluid,
while maintaining a constant amount of antigen.
dim
In flow cytometry, indicates the relative fluorescence intensities
of cells being analyzed. Dim represents the lowest
intensity, in contrast to bright, which designates the greatest
intensity of fluorescence.
Dr. Dimsdale, a pioneer in smallpox vaccination.
Dimsdale, Dr. Thomas (1712–1800)
Of Hertford, wrote a popular and successful book entitled
The present method of inoculating for the smallpox. He
successfully inoculated Catherine the Great of Russia, her
young son, the Grand Duke, and others, which popularized
inoculation in Russia.
Cl
NO 2
NO 2
1-chloro-2, 4-dinitrobenzene
Dinitrochlorobenzene.