Abstract: This invention is directed to a novel group of compounds, herein termed Recognins. Recognins are made by treating malignant tumor cells or artificial cancer cells and separating the desired products. The Recognins may be used to prepare their Chemoreciprocals, i.e., by contacting the Recognins or the Recognins on a support with body fluids. These Chemoreciprocals are useful for diagnostic and therapeutic purposes, i.e., for diagnosing and treating cancers. The Chemoreciprocals are substances which react with immunochemical-like specificity with a Recognin in vivo or in vitro, e.g., in a quantitative precipitin test, in Ouchterlony double diffusion or in immunofluorescence.