Quantitation of angiogenesis factor in bovine retina and tumour extracts by means of radioimmunoassay.

Using an antiserum raised against tumour angiogenesis factor (TAF) we have developed a radioimmunoassay for retina and tumour angiogenesis factor(s). This antiserum was previously shown to bind to both human and animal tumour extracts and to inhibit the angiogenesis induced by TAF in vivo. TAF from rat Walker tumour was used for iodination by the chloramine-T method. An excess of 125I-labelled TAF was incubated with TAF antibody in the absence (maximum binding) and presence (inhibition of maximum binding) of unlabelled tissue extract. A double antibody technique was used to separate free and bound TAF. Unlabelled human Wilms tumour TAF was used as a standard. The extent of inhibition of 125I-TAF-anti-TAF binding provided a measure of TAF in tissue extracts examined. Extracts of normal bovine retina, cornea, lung, aorta, lymph nodes, iris, vitreous humour, and human tumours and normal human pituitary and liver were assayed. Only bovine retina and human tumours were found to contain angiogenesis factor. These findings, together with our earlier results, suggest that angiogenesis factor from both bovine retina and human tumours induce angiogenesis in vivo and possess common antigenic determinants. The presence of angiogenesis factor in healthy retina and its relationship to neovascularisation in clinical conditions is discussed.