Release of Paramecium immobilization antigen to the non-nutrient medium.

The instability of Paramecium aurelia surface components has been shown: after 60 min incubation of dense cell suspension ((1-2 . 10(6) cells per ml) in Tris-Ca buffer at 4 degrees C or 23 degrees C the surface coat was partially stripped off and the proteins were released to the medium. The electrophoretic analysis of the released proteins shows one major band of mol. wt. 280,000--300,000 and some minor bands. The major released protein is the immobilization antigen as proved using immunodiffusion test and antibody precipitation technique.