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follicular lymphoma 281 foscarnet
in the follicles. Follicular hyperplasia is often a postinfection
reactive process in lymph nodes.
follicular lymphoma
The most common form of non-Hodgkin lymphoma in
the United States, comprising approximately 45% of adult
lymphomas. The neoplastic cells closely resemble normal
germinal center B cells. They resemble normal follicular
center B cells, expressing CD19, CD20, CD10, and monotypic
surface immunoglobulin. CD5 is not expressed, which
differentiates follicular lymphoma from B cell chronic
lymphocytic leukemia (CLL), small lymphocytic lymphoma
(SLL), and mantle cell lymphoma. Follicular lymphoma
cells express BCL2 protein, in contrast to normal follicular
center B cells that are BCL2-negative. A 14;18 translocation
is characteristic of follicular lymphoma, in which juxtaposition
of the IgH locus on chromosome 14 and the BCL2
locus on chromosome 18 occurs.
food allergy
Type I (anaphylactic) or type III (antigen–antibody complex)
hypersensitivity mechanism responses to allergens or
antigens in ingested foods may lead to intestinal distress,
producing nausea, vomiting, and diarrhea, along with
edema of the buccal mucosa, generalized urticaria, or
eczema. Food categories associated with allergies in some
individuals include eggs, fish, nuts, peanuts, soy, and wheat.
Atopic sensitization to cow’s milk is the most common food
allergy; casein is the major allergenic and antigenic protein
in cow’s milk. Both skin tests and RAST tests using the
appropriate allergen or antigen may identify individuals
with a particular food allergy.
food and drug additive reactions
Urticaria and angioneurotic edema are the main symptoms.
footprinting
A method to ascertain the DNA segment (or segments) that
binds to a protein. Radiolabeled double-stranded DNA is
combined with the binding protein to yield a complex that
is exposed to an endonuclease that cuts the molecules once
and at random. The digested DNA is electrophoresed in
polyacrylamide gel together with a control DNA sample
(treated similarly, but without added protein) to permit
separation of fragments differing in length by one nucleotide.
Autoradiography of the material reveals a series
of bands representing the DNA fragments. In the area of
protein binding, the DNA is spared from digestion, and no
corresponding bands appear compared to the control. The
protected area’s specific location can be ascertained by running
a DNA sequencing gel in parallel.
footprints
Macrophages filled with Mycobacterium leprae without
caseation necrosis. A similar situation may be observed
in anergic Hodgkin disease patients and in AIDS patients
infected with M. avium-intercellulare.
forbidden clone theory
According to this hypothesis, self-reactive lymphocyte clones
are eliminated in the thymus during embryonic life, but
subsequent mutation may permit the reappearance of selfreactive
clones of lymphocytes that induce autoimmunity.
foreign gene
See transgenic mice.
formol toxoids
A toxoid generated by the treatment of an exotoxin such as
diphtheria toxin with formalin. Although first used nearly
a century ago, it was subsequently modified to contain an
adjuvant such as an aluminum compound to boost immune
responsiveness to the toxoid. It was later replaced with
the so-called triple vaccine for diphtheria, pertussis, and
tetanus.
formyl–methionyl–leucyl–phenylalanine (F–Met–Leu–Phe)
A synthetic peptide that is a powerful chemotactic attractant
for leukocytes, facilitating their migration. It may also
induce neutrophil degranulation. It resembles chemotactic
factors released from bacteria. Following interaction
with neutrophils, leukocyte migration is enhanced, and
complement receptor 3 molecules are increased in cell
membranes.
Forssman antibody
An antibody specific for the Forssman (heterogenetic)
antigen. Human serum may contain Forssman antibody as a
natural antibody.
Forssman antigen
A heterophil or heterogenetic glycolipid antigen that
stimulates the synthesis of anti-sheep hemolysin in rabbits.
Its broad phylogenetic distribution spans both animal and
plant kingdoms. The antigen is present in guinea pig and
horse organs, but not in their red blood cells. In sheep, it is
found exclusively in erythrocytes. Forssman antigen occurs
in both red blood cells and organs in chickens. It is also
present in goats, ostriches, mice, dogs, cats, spinach, and
Bacillus anthracis and on the gastrointestinal mucosa of a
limited number of people. It is absent in rabbits, rats, cows,
pigs, cuckoos, beans, and Salmonella typhi. Forssman substance
is ceramide tetrasaccharide. The Forssman antigen
contains N-acylsphingo-sine (ceramide), galactose, and
N-acetylgalactosamine. As originally defined, it is present
in guinea pig kidney and is heat-stable and alcohol-soluble.
Forssman antigen-containing tissue is effective in absorbing
the homologous antibody from serum. Antibodies to the
Forssman antigen occur in the sera of patients recovering
from infectious mononucleosis.
Forssman, Magnus John Karl August (1868–1947)
Swedish professor for whom the heterophile antigen was
named, following his discovery and work with that protein.
forward-angle light scatter (FALS)
In flow cytometry, particle size is measured by the amount
of scattered light (0.5 to 2 degrees) detected as the focused
laser beam encounters the cell and continues as scattered
light to the forward-angle light scatter detector.
forward genetics approach
Mutating a gene in an experimental animal to prove that
gene’s role in a particular disease and determining whether
the mutation produces the disease of interest.
Na
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P
O
Na
foscarnet
An investigational drug used to combat cytomegalovirusinduced
pneumonia, hepatitis, colitis, and retinitis in
AIDS patients rendered nonresponsive to gancyclovir,
C
Foscarnet.
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O
Na
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