A radioimmunoassay for the quantification of human ubiquitin in biological fluids: application to parasitic and allergic diseases

Purified ubiquitin has been shown to share similar biological and physicochemical properties with a previously characterized lymphokine, platelet activity suppressive lymphokine (PASL). This lymphokine, which inhibits the cytotoxic function of activated platelets, is produced during schistosomiasis and Hymenoptera venom hypersensitivity (HVH). We have developed a radioimmunoassay specific for ubiquitin, in order to determine the ubiquitin levels in human sera and plasma from patients with these pathologies. The working range of the assay was between 60 and 500 ng/ml, and the sensitivity was 8–10 ng/ml. The reproducibility, specificity and accuracy were determined under standard condition (PBS-0.3% BSA) and using different biological fluids (human serum, plasma and T lymphocyte supernatant). Using this assay, we found that the ubiquitin concentrations were higher in both schistosomiasis and HVH (up to 150–300 ng/ml) compared with sera and plasma from healthy donors where the ubiquitin levels did not exceed 50 ng/ml.