Described as secreting a mouse monoclonal antibody (IgG1) reacting with neonatal and adult slow and IIA fibers in rat and human and with slow and IIA fast myosin heavy chains in Western blots; the cell line was established in 1985 by fusion of X63AG8.653 cells with spleen cells from a BALB/c mouse that had been immunized with human skeletal muscle myosin