Absorption of ablastic activity from mouse serum by using a Trypanosoma musculi population rich in dividing forms

An in vivo assay of ablastin activity was developed by passive transfer of ablastic serum into nude mice. Preparations of Trypanosoma musculi that contained 35 to 50% dividing forms removed ablastic activity from mouse serum, but absorption of serum with a parasite preparation consisting of less than 5% dividing forms did not appreciably alter ablastic activity. These data suggest that ablastin is an antibody that can be absorbed onto homologous trypanosomes.