At an E:T ratio of 2:1, 5:1, and 10:1 EM801 induces a killing of MM cells of 60, 70, and 80% respectively and the depletion of a subpopulation of T lymphocytes (CD4+ or CD8+) not significantly reduces the cytocidal effect of the antibody. The gene discussed is CD4; the disease is Miyoshi myopathy.