Untitled - D Ank Unlimited

Hassall’s corpuscles 311 HAT medium
Hashimoto’s thyroiditis.
Hashimoto’s thyroiditis.
Antibody to thyroid microsomal antigen
and
Antibody to thyroglobulin
Hashimoto’s thyroiditis.
by lymphocyte, plasma cell, and macrophage infiltration and
often formation of lymphoid germinal centers. The thyroid
becomes firm and enlarged. There is lymphocytic infiltration
and oxyphilic alteration of the thyroid follicular epithelium.
Thyroid follicles exhibit permanent germinal centers, and
the thyroid epithelium is atrophied. Autoantibodies against
thyroid peroxidase (microsomal antibodies), thyroglobulin,
and colloid are demonstrable. The antibodies against
thyroid-specific antigens recruit natural killer (NK) cells
to the thyroid, leading to tissue injury and inflammation.
Destruction of thyroid follicular cells by a cell-mediated
response leads to insufficient synthesis of thyroxine, producing
hypothyroidism. Even though the thyroid gland increases
in size, the acinar epithelium is continually destroyed. Thus,
the principal pathogenesis is by autoimmune mechanisms.
The disease leads to a decrease in thyroid function. This
is considered to be an organ-specific autoimmune disease.
Hormonal replacement therapy is used for treatment. Also
called chronic autoimmune thyroiditis.
Hassall’s corpuscles.
Normal thymus. This child’s thymus shows the dense cortex composed
predominantly of lymphocytes and the less dense medulla with fewer
lymphocytes. Note the Hassall’s corpuscle.
Hassall’s corpuscles
Epithelial cell whorls in the medulla of the thymus. They
are thought to produce thymic hormones. Whereas the
center may exhibit degeneration, cells at the periphery may
reveal endocrine secretion granules.
HAT medium
A growth medium used in tissue culture of animal cells that
contains hypoxanthine, aminopterin, and thymidine and
is used to selectively isolate hybrid cells. Aminopterin, a
folic acid antagonist, blocks nucleic acid de novo synthesis
but does not have this effect for synthesis by the salvage
pathway mechanism. Hypoxanthine and thymidine are substances
from which nucleic acid can be synthesized by the
second mechanism. The enzymes hypoxanthine-guanine
phosphoribosyl transferase (HGPRT) and thymidine kinase
are requisite for the salvage pathway. Thus, HAT medium
cannot sustain cells lacking these enzymes, as nucleic
acid synthesis is totally inhibited. However, hybrid cells
produced from each of the two cell lines whose enzyme
defects are different can survive and grow in HAT medium.
This makes it a useful selective medium for hybrid cells. It
is widely employed in hybridoma production, as it permits
myeloma cell–lymphocyte hybrids to survive. Nonfused
myeloma cells die for lack of HGPRT, and unfused
H