Migration inhibition of peritoneal exudate cells from sensitized and desensitized rats.

The migration of peritoneal exudate cells (PEC) from rats with delayed skin reactivity to diphtheria toxoid (DT) and tuberculin (PPD) was inhibited in the presence of antigen. Three days after an intravenous injection of 2.5 mg of DT there was no inhibition with DT. Seven and 28 days later migration was inhibited but less than in sensitized controls. In 6 weeks the difference disappeared. Three days after the DT challenge, the migration inhibition with PPD was weaker than in the sensitized controls. From day 7 on, non-specific reduction of migration inhibition was not detected. The 24-hour skin reactivity to DT and PPD closely paralleled the in vitro phenomena. The mechanism of desensitization appears to be the lack or a functional defect of the specific cells or a blocking factor unremovable by washing or produced during the migration assay.