Behavior of Acid-Treated Antipneumococcal Rabbit Antibodies

Summary 1.Pneumococcal rabbit antibody treated with acid shows an increase of nitrogen precipitable by S. 2.A shift in the combining ratio occurs at the same time. 3.The ratio of mouse-protective value / N precipitated by S is lowered. 4.The complement-fixing quality of acid-treated sera is impaired or lost when the ratio of mouse-protective power / N precipitable is lowered. Loss of complement-fixing quality was also observed with antibody subjected to a process of partial peptic digestion. 5.The properties of causing capsular swelling and of eliciting passive anaphylactic shock are unimpaired in acid-treated sera. 6.The implications of these observations are discussed.