Clonal and temperature induced differences in serotypes in the ciliate Dileptus anser

Abstract

Antigenic differences have been demonstrated in 20 clones of the ciliate Dileptus anser by immobilization assay, precipitation reaction in agar and immunofluorescence, using antisera obtained against two of these clones. Homologous clones reacted with antisera in high dilutions. 7 heterologous clones demonstrated a slight reaction of immobilization. 13 heterologous clones failed to react with immune sera, which allowed to attribute them to some other serotypes. By immunodiffusion methods the presence of an antigen expressed in a single clone has been shown. When testing a certain clone with the homologous immune serum by immobilization reaction and immunofluorescence, the subclones cultured at 17°C and 25°C express two different serotypes each. When cultivating the same clone at 19 °C, 21 °C or 23 °C, the cells express both of these serotypes, although to a different extent depending on the temperature of their cultivation. Heterologous clones often show cross-reactions with the same immune sera, usually when the ciliates are cultivated at the same temperature as the cells used for immunization. The change of cultivation temperature from 17°C to 25 °C, or vice versa, leads to a gradual replacement of one serotype with another. This transformation of serotypes induced by the change in cultivation temperature was completely reversible, and judging by the immunofluorescence data, occurred in most of, if not in all, the cells. The new serotype appeared and the old one disappeared at the same rate and took 6 to 7 days at 17 °C and 3 to 4 days at 25 °C. In both cases 6 to 8 cell divisions took place during that time.