ABSTRACT
Ten mouse monoclonal antibodies (mAbs) were raised against trichocyst contaminants present in crude or enriched lysosome fractions of Paramecium multimicronucleatum. Using an indirect immunofluorescence assay (IFA) and immunogold labelling on frozen thin sections, epitopes were located on the outer edge, cortex and the core of the trichocyst body, as well as the sheath covering the tip. Except for the two on the tip, epitopes were reactive after SDS-PAGE under non-reducing conditions. Four mAbs (131C1E8, Al–3, A16–2, D7) were directed to a trio of bands of 37, 34 and 29 (× 103) Mr from the beaded or meshlike trichocyst body sheath. A fifth mAb (135B9E7), directed to epitopes on the cortex inside the beaded body sheath, reacted strongly with the 37 and 34 bands, but weakly with the 29×103Mr band. The last three mAbs (270D5, 22C7F2, D8) were reactive with one or more of three families of antigens found on the trichocyst core. mAb 270D5 reacted mainly with the 34 and 29(×103)Mr bands of the family containing the above trio, while mAb 22C7F2 reacted consistently with the 47×103 band of the higher Mr family but variably with both the trio of bands and the 17×103 band of the lower Mr family. mAb D8, which was directed to epitopes on the trichocyst core and small vesicles in the endoplasm, reacted only with the 29×103Mt band. The mAbs were cross-reactive with the trichocysts of P. primaurelia, P. tetraurelia, P. caudatum and P. calkinsi with some small variation in blotting patterns. Except for the reactivity of mAbs 22C7F2 and 270D5 with a 64×103Mr band, Tetrahymena thermophila was unreactive with these mAbs either by IF A or after SDS–PAGE and blotting. These results show that: (1) the mAbs obtained are specific for selected polypeptides in four trichocyst locations; (2) antigenic differences exist within the core, cortex and the beaded sheath of the trichocyst body; and (3) the antigenic determinants were conserved in all paramecia species tested.
