PDCD1 and dilated cardiomyopathy: Additionally, Nishimura et al. demonstrated that mice deficient of programmed cell death protein-1 (PD-1-/-, a key factor for B-cell differentiation) expressed elevated levels of circulating autoantibodies that bound specifically to cardiomyocytes and were associated with progression of dilated cardiomyopathy (Nishimura et al., 2001).