UCN2 and myositis disease: That these effects were due to anti-SRP autoantibodies rather than other serum components was supported by the finding that preincubation with sera from a normal human control or from polymyositis patients containing either no detectable myositis autoantibodies (serum 5–15) or with anti-Jo-1 autoantibodies directed against histidyl-tRNA synthetase (serum 1–24) had little or no effect on PPL translocation (Figure 1, lanes 9, 39 and 45), and the finding that protease-protected PL was observed in all cases (Figure 1, lanes 10, 40 and 46).