Human TNF-Alpha ELISA

Intended use

The Human TNFα ELISA kit is a solid phase sandwich ELISA for the in-vitro qualitative and quantitative determination of TNFα in supernatants, buffered solutions or serum and plasma samples. This assay will recognise both natural and recombinant human TNFα.

Summary

Tumor Necrosis Factor (TNFα), also known as cachectin, is a polypeptide cytokine produced by monocytes and macrophages. It functions as a multipotent modulator of immune response and further acts as a potent pyrogen (4, 17). TNFα circulates throughout the body responding to stimuli (infectious agents or tissue injury), activating neutrophils, altering the properties of vascular endothelial cells, regulating metabolic activities of other tissues, as well as exhibiting tumoricidal activity by inducing localized blood clotting. TNFα also inhibits lipoprotein lipase activity resulting in cachexia, a physical wasting condition (4, 17). Activation of B-cells by the Epstein Barr virus can be inhibited by TNFα (15). Due to its varied actions throughout the immune system, TNFα may play a role in the pathogenesis of many disease states. TNF-α production is mediated by the action of lymphokines and endotoxins on the macrophage. Purified monocytes produce TNFα within four hours of stimulation by recombinant IL-2 (9) and there is some in vitro evidence to suggest that TNFα is expressed at high levels and with prolonged kinetics in T cells stimulated by both CD2 and CD28 (5). Secretion of TNFα is enhanced by gamma interferon. TNFα then induces or enhances the specific production of Class I MHC antigen, GM-CSF, and IL-1. Recent evidence has suggested an intracellular role for this peptide (23).

TNFα may play a significant role in the pathogenesis of inflammatory disease of the joints and other tissues. Chin et al. (6) found that TNFα, along with gamma interferon and IL-1 increased cell surface expression of ICAM-1 on synovial fibroblasts. Alvaro-Garcia et al. (3) reported that TNFα stimulates synovial proliferation.

Waage et al. (25) found that increased levels of TNFα in patients with septicemia and meningococcal disease correlated with fatal outcome. Scuderi et al. (22) suggest that increased levels of this cytokine may play a role in the host defense mechanism against parasitic infections. Girardin et al. (12)reported that increased serum TNFα levels correlated with the number of risk factors involved inchildren with gram-negative sepsis and purpura fulminians. Elevated levels of TNFα were also found inindividuals suffering from myocarditis (11).

Role for TNFα in the pathogenesis of AIDS has also been pointed out. Alveolar macrophages (AM) from HIV positive individuals with opportunistic lung infections have been shown to spontaneously produce higher levels of TNFα in vitro than those HIV positive individuals without infection and HIV negative controls (14, 16). Krishnan et al. (16) report that higher TNFα production by AM was associated with lower counts of pneumocystis carinii in broncheoalveolar lavage fluid, indicating that TNFα may play a role in the control of this infection in AIDS. Israel-Biet et al. (14) also reported in in vitro studies, that AM that express HIV (p24+) released significantly higher levels of TNFα than p24- alveolar macrophages and controls. Reddy et al. (20) found persistently elevated levels of circulating TNFα in HIV seropositive individuals and suggest a possible involvement of this cytokine in the development of AIDS.

Measurement of TNFα levels has also been shown to be useful in transplant research, where Maury et al. (18)and McLaughlin et al. (19). Both reported TNFα to be markedly elevated in renal allograft rejectionepisodes. Recent evidence has been presented on increased TNFα levels in Bone Marrow Transplant(BMT) (13, 21). BMT patients with major transplant related complications such as interstitial pneumonitisand severe acute graft-versus - host disease had TNFα levels significantly increase over controls (13).

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