The Development of the Phage-Inactivating Properties of Serum During the Course of Specific Immunization of an Animal: Reversible and Irreversible Inactivation

Summary Sera obtained from early and late bleedings of the same animal during the course of immunization against bacteriophage T4 are different in character. Among the T4 particles inactivated by such sera two fractions can be distinguished, one of which can be reactivated on dilution, the other not. In late serum the former fraction is minute; inactivation is practically irreversible. In early serum a large fraction of the inactivated particles can be reactivated on dilution. Reactivation is approximately a first order process. The rate of reactivation is decreased by lowering the temperature or the ionic strength of the medium.