an agent or element that contributes to the production of a result. In epidemiology and statistics called also a variable because the factor may have a number of values. In an experiment a factor is a type of treatment and in the experiment the factor will be represented in different groups by different values. Such a factor may originate spontaneously or be introduced by an investigator.
a statistical method for analyzing the correlations between several variables.
antinuclear factor (ANF)
a complement component (C3 proactivator) that participates in the alternate complement pathway.
C3 nephritic factor
a gamma globulin that is not an immunoglobulin, which is found in the plasma of certain individuals with membranoproliferative glomerulonephritis associated with hypocomplementemia; it initiates the alternate complement pathway.
clotting f's, coagulation f's
factors essential to normal blood clotting, whose absence, diminution or excess may lead to abnormality of the clotting mechanism. See also clotting
a factor that, when activated, serves as a serine esterase in the alternate complement pathway.
a hematopoietic vitamin that combines with intrinsic factor for absorption from the intestine and is needed for erythrocyte maturation; called also cyanocobalamin and vitamin B12.
F factor, fertility factor
the plasmid that determines the mating type of conjugating bacteria, being present in the donor (male) bacterium and absent in the recipient (female).
f's I to XIII
factors and names of individual factors.
factor VIII activity
a test for hemophilia
A; activity is measured in biologic assays using factor VIII-deficient plasma as the substrate.
factor VIII-related antigen
von Willebrand antigen.
factor IX deficiency
see plasma thromboplastin component (PTC).
factor IX complex
a sterile, freeze-dried powder containing coagulation factors II, VII, IX and X.
factor X deficiency
see stuart factor.
fibrin stabilizing factor
factor XIII, one of the blood clotting factors that converts soluble fibrin monomer to insoluble, stable fibrin polymer.
a glycoprotein secreted by the parietal cells of the gastric glands, necessary for the absorption of vitamin
(cyanocobalamin, extrinsic factor). Its absence in humans results in pernicious anemia. Porcine stomach is a very rich source.
an immunoglobulin (a 7S antibody) that reacts with leukocyte nuclei, found in the serum in systemic lupus erythematosus.
a relationship between observable manifestations (or variables) and the underlying factors affecting the variables.
lymph node permeability factor (LNPF)
a substance from normal lymph nodes which produces vascular permeability.
lymphocyte transforming factor (LTF)
a lymphokine causing transformation and clonal expansion of lymphocytes.
osteoclast activating factor
substance produced by lymphocytes which facilitates bone resorption.
factors important in hemostasis that are contained in or attached to the platelets. See also platelet
platelet-activating factor (PAF)
an immunologically produced substance which leads to clumping and degranulation of blood platelets.
R factor, resistance factor
a bacterial plasmid (R plasmid) which carries genes for antimicrobial resistance; it can be transmitted to other bacterial cells by conjugation, as well as to daughter cells.
a protein that binds directly to any stop codon
that reaches the A site on the ribosome.
factors elaborated in one structure (as in the hypothalamus) that effect the release of hormones from another structure (as from the anterior pituitary gland), including corticotropin releasing factor, melanocyte-stimulating hormone releasing factor and prolactin releasing factor. Applied to substances of unknown chemical structure, while substances of established chemical identity are called releasing hormones.
transfer factor (TF)
a factor released from sensitized lymphocytes that has the capacity to transfer delayed hypersensitivity to a normal (nonsensitized) animal. See also transfer factor