Characterization of monoclonal anti-DNA antibodies and visualization of binding to chromosomes and cell nuclei

Monoclonal antibodies against DNA from two hybridoma cell lines were produced and characterized. One had specificity for single stranded (ss) DNA with some cross-reactivity to RNA, while the other was specific for both single (ss) and double stranded (ds) DNA. The latter ds and ss DNA-binding antibody was used as a model for analysing the distribution of the epitope in chromosomes and cell nuclei. A linear correlation between antibody binding and propidium iodide counterstaining was found on flow cytometric analysis of suspended chromosomes. Immunofluorescence of rat myoblast cells showed a speckled distribution of the antibody in the nucleus with a variability between the cells. Using electron microscopy to visualize antibody binding with gold particles, codistribution with uranyl acetate staining of leucocytes was found. These results suggested that the antibody preferentially binds to condensed chromatin in cells and chromosomes.