Characterization of receptors for human tumour necrosis factor and their regulation by gamma-interferon.
Tumour necrosis factors, TNF-alpha and TNF-beta (previously called lymphotoxin), are the products of activated monocytes and lymphocytes, respectively, and both have recently been purified, sequenced and cloned by recombinant DNA methods, revealing 35% identity and 50% homology in the amino-acid sequence. Both proteins have been found to be specifically toxic to many tumour cells. Furthermore, it has been reported that various interferons are synergistic with TNF for anti-tumour effects in vitro, while activities attributed to the two proteins have also been shown to necrotize various tumours in vivo. We have now prepared 125I-labelled highly purified recombinant human TNF-alpha to study in detail its binding to the human cervical carcinoma cell line ME-180. Our results indicate that there is a single class of specific high-affinity receptors for TNF on this cell line which has a Kd of about 0.2 nM and an average of 2,000 receptor sites per cell. The binding of labelled TNF-alpha to these cells can be inhibited by both TNF-alpha and TNF-beta but not by gamma-interferon (IFN-gamma). However, preincubation of cells with IFN-gamma increases the total number of TNF receptors two to threefold without any significant change in the affinity constant. This is the first report that TNF-alpha and -beta share a common receptor and that the receptors can be up-regulated by interferon. Our results may explain previous observations regarding similar biological activities observed for these two cytotoxic proteins and also their synergistic action with interferons.
D002460:Cell Line; D005260:Female; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D007455:Iodine / Q000378:metabolism; D008970:Molecular Weight; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha; D002583:Uterine Cervical Neoplasms / Q000032:analysis
D006023:Glycoproteins; D011956:Receptors, Cell Surface; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D007455:Iodine