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Results of this test are labeled for research purposes only by the assay's manufacturer. The performance characteristics of this assay have not been established by the manufacturer. The result should not be used for treatment or for diagnostic purposes without confirmation of the diagnosis by another medically established diagnostic product or procedure. The performance characteristics were determined by LabCorp.
Enzyme-linked immunosorbent assay (ELISA)
Tumor necrosis factor-α (cachectin) and tumor necrosis factor-β (lymphotoxin) are two closely related proteins that share sequence homology of 34% in their amino acid sequence. Both mediators act on their target cells via the same receptors and, therefore, show similar, but not identical, biological effects. Under denaturing conditions TNF-α is a 17-kilodalton, nonglycosylated protein. The biologically active form of TNF-α is a trimer. Besides this soluble form of TNF-α, a 28-kilodalton membrane-bound form occurs on cell surfaces of TNF-producing cells, which may serve as a pool for soluble TNF-α and can be proteolytically cleaved from the cell surface.
Different cells are shown to produce TNF-α: For example, macrophages, CD4+ T cells and NK cells after stimulation with lipopolysaccharides. Additionally, smooth muscle cells, polymorphonuclear neutrophils, astrocytes and a variety of tumor cell lines can produce TNF-α. TNF-α acts via two distinct cell surface receptors, which are called TNF receptor I, and TNF receptor II. These receptors can be identified on virtually all cell types except erythrocytes. Besides the cell-bound forms of TNF receptors, soluble forms are known to be capable of TNF-α binding. They compete, therefore, with the cell-bound forms and can inhibit the effects of TNF-α.
Due to the occurrence of TNF-α receptors on nearly all cells, TNF-α demonstrates a wide variety of biological action. It has cytolytic and cytostatic effects on tumor cells and shows chemotactic activity on neutrophils. TNF-α is a growth factor for fibroblasts and stimulates the synthesis of collagenase and prostaglandin E2 bone resorption can be induced by TNF-α because it activates osteoclasts. TNF-α enhances the proliferation of T cells after stimulation with IL-2. In the absence of IL-2, TNF-α induces the proliferation and differentiation of β cells.
TNF-α serum or plasma levels may be elevated in sepsis, autoimmune diseases, various infectious diseases, and transplant rejection.
0.4 mL (Note: This volume does not allow for repeat testing.)
Red-top tube or gel-barrier tube
Transfer the serum into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp N° 49482). Freeze immediately and maintain frozen until tested. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.
Causes for Rejection
Nonfrozen specimen; nonserum specimen; gross lipemia; gross hemolysis
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|140673||Tumor Necrosis Factor-Alpha||3074-2||140682||Tumor Necrosis Factor-Alpha||pg/mL||3074-2|