Developmental expression of macronuclear specific antigen in Paramecium caudatum.

We obtained a monoclonal antibody (MA-1) specific for macronuclei of the ciliate Paramecium caudatum and P. dubosqui. Immunoblotting showed that the antigen was a polypeptide of 50 kilodalton (kDa). During the process of nuclear differentiation in P. caudatum, the MA-1 antigens appeared in the macronuclear anlagen immediately after four out of eight post zygotic nuclei differentiated morphologically into the macronuclear anlagen. Afterwards, the antigens could be detected in the macronucleus through the cell cycle, and disappeared when the macronucleus began to degenerate in exconjugant cells. These results suggest that the antigens may play a role in the differentiation and function of the macronucleus.