Immunoelectron and immunofluorescence localization of desmin in mature avian muscles.

Antisera or affinity-purified antibodies shown to be specific for avian gizzard desmin antigen by double immunodiffusion, antigen-blocking, and immunoautoradiography experiments have been used in indirect immunofluorescence and indirect immunoelectron microscopy to demonstrate localization of desmin in myofibrils from mature avian muscles. The light microscope results agree with the work of others in that they suggest that desmin is primarily at or near the periphery of Z-lines of striated muscle myofibrils. Immunoperoxidase labelling more clearly shows that the reactive desmin antigen is located almost entirely between Z-lines of adjacent parallel myofibrils and that there is no obvious correlation between locations of T-tubules and desmin structures. The electron-dense reaction product often followed an approximately linear course between Z-lines of adjacent myofibrils and indicated the desmin antibodies had decorated a small number of filaments spanning this region. These results suggest that the desmin found in close association with myofibrils of mature striated muscle is in the aggregated form of 10-nm filaments.