The Surface Antigens of Paramecium aurelia

Abstract

Antisera against the various serotypes of Paramecium aurelia are prepared by injecting homogenates of mechanically disrupted organisms into a rabbit (Sonneborn, 1950). These antisera contain antibodies against antigens other than the immobilization antigen (van Wagtendonk & van Tijn, 1953). In an effort to obtain partially purified preparations of the immobilization antigen, preparatory to .the determination of its chemical constitution, a method was devised to obtain the antigen without disrupting the cell. This antigen prepartion which includes the trichocysts, but not the cilia, will be referred to as the ' surface antigen preparation '. The properties of this preparation are described in this communication. RESULTSParamecium aurelia, var. 4, stock 51.7, serotype A was grown in a bacterized lettuce extract medium. Several litres of a 24 hr. old culture were first concentrated by filtration through a Berkefeld filter. The organisms were then concentrated and partially freed from bacteria by electromigration through a sterile salt solution (van Wagtendonk, Simonsen & Zill, 1952). The volume of the concentrated organisms was carefully measured and the number of P. aurelia present determined by a count of samples of a suitable dilution. Molar NaCl solution was added to the suspension to reach a final concentration of 0-06 M. The mixture was gently shaken for 1 min. and centrifuged for 2 min. a t 600g. The supernatant fluid, containing the trichocysts (microscopical examination showed the absence of cilia) was carefully decanted and saved. The sediment was resuspended in 0.06 M-NaCl solution and treated in the same way. The two supernatant suspensions were combined, centrifuged for 1 hr. a t 2OOOg in a refrigerated centrifuge, dialysed for 24 hr. against running distilled water and finally concentrated by lyophilization.The number of organisms present after the first treatment and after the second treatment was determined by a count of the organisms present in a suitable dilution and the loss by lysis calculated. It can be seen from Table 1