The mechanisms of increasing of polyreactive immunoglobulin (PRIG) activity in vivo are suggested. It was shown that at some conditions, which can be observed in organism in sites of inflammation, activity of serum PRIG could be enhance considerably. This enhancing might be induced either by reactive oxygen species, mainly by hydroxyl radicals, or by lipases. The increasing of PRIG activity could be not only a result of preexisting PRIG unblocking, but also a result of transformation specific antibodies into PRIG, caused by peroxide degradation or lipolysis of lipids, tightly but noncovalently linked to antibodies, either by hydroxyl radicals or lipase. It was also suggested that most (if not all) specific antibodies consist of not only polypeptide chains, but also some lipids. Deprived of these lipids antibodies loose their specificity and transform into polyreactive immunoglobulins.