1. The 11 S component of normal human serum is required in the initial cold phase of the Donath-Landsteiner reaction, an autoimmune hemolytic reaction entirely of human origin.

  2. The 11 S component is present in crude preparations of C′1-esterase, and removal of 11 S renders C′1-esterase inactive in the cold phase of the reaction.

  3. The 11 S component precedes C′1-esterase in the initiation of the hemolytic reaction, and, in contrast to C′1-esterase, is not inhibited by Na3HEDTA or serum inhibitor of C′1-esterase.

1

Presented in part at the 54th annual meeting of the American Society of Clinical Investigation, Atlantic City, N. J., April 29, 1962; supported in part by Grant H 1263C, National Heart Institute, National Institutes of Health, USPHS.

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Copyright, 1963, by The Williams & Wilkins Company
Copyright © 1963 by The American Association of Immunologists, Inc.
1963
The Williams & Wilkins Company