Antibodies against Z DNA react with the macronucleus but not the micronucleus of the hypotrichous ciliate stylonychia mytilus

Using indirect immunofluorescence, we studied the reaction of antibodies specific for left-handed Z DNA with the nuclei of the hypotrichous ciliate Stylonychia mytilus. In the vegetative cell, the macronucleus reacts strongly with these antibodies, but no reaction can be detected with micronuclei. However, an antibody that binds to denatured and right-handed B DNA reacts with both types of nuclei. No reaction of the anti-Z DNA antibody is seen in the macronuclear replication band. Digestion of macronuclei with DNAase I leads to a decrease in the anti-Z DNA antibody reaction. Some stages of the developing macronucleus were also investigated. No reaction is seen at the polytene chromosome stage, but following DNA elimination the nucleus is seen to react with the antibody.