isocytolysin

[ī′sō-sī-tŏlĭ-sĭn]
n.
  1. A cytolysin that reacts with the cells of certain other animals of the same species, but not with the cells of the individual that formed it.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.