Abstract
Human and monkey sera containing autoantibodic to protamines reveal often strong cross-reactions with protamines of other species including salmon protamine. These cross-reactions can be readily detected both in the immunofllorescence test and the micro-complement fixation test. These sera react to a much lesser extent witn poly-L-argirine. The results indicate that the cross-reactions of these protamines are not primarily due to clusters of arginine.