Lack of Correlation between in vivo Peroxidatic Activity Patterns and Tumoricidal Activity in vitro of Peritoneal Macrophages after Intraperitoneal Im

Abstract

Immunization of C57BL mice with one inoculum of 10 7 DBA/2-derived SL2 lymphosarcoma cells resulted in a ± 20-fold increase in the total number of peritoneal cells. The number of macrophages showed a 10-fold increase from 3 × 10 6 (control mice) to 3.4 × 10 7 cells at day 8 after immunization. Within this macrophage population, four different cell types, based on the ultrastructural peroxidatic activity patterns, could be distinguished: exudate macrophages, resident macrophages, resident- exudate macrophages and Peroxidatic-activity- negative macrophages. The number of exudate macrophages significantly increased in the peritoneal cavity after immunization: at day 8 after immunization, a peak value of 10 7 cells was observed. At the same time, there were 2.2 × 10 7 peroxidase-activity- negative macrophages present (representing the control value × 50). Significant in vitro tumoricidal activity of the isolated macrophages could not be measured until 8 days after immunization. At that time, a cytotoxicity index of 68 was reached. After immunization of the C57BL mice with 3 injections with allogeneic SL2 cells, there were no dramatic changes in the number of peritoneal cells after the last immunization. Only immediately after the last immunization was a minor increase in Peroxidatic-activity- negative macrophages seen. But already at 5 days after the last immunization, the composition of the peritoneal suspension was similar to that of non-immunized mice with predominantly resident macrophages. The cytotoxicity of the peritoneal macrophages from hyperimmunized mice was constantly high during 1-15 days after the last immunization (cytotoxicity index ranged from 66-72). In order to study which type(s) of macrophage(s) (resident, exudate, resident- exudate or Peroxidatic-activity-negative) is/are responsible for the cytotoxicity measured in vitro, peritoneal cell suspensions (obtained after immunization) were fractionated according to their affinity to wheat germ agglutinin (WGA) coupled to Sepharose columns. Comparison of the values of cytotoxicity measured before and after separation into ≪subtypes≫ of the macrophages revealed that the expression of cytotoxicity is not correlated with any of the ≪sub-types≫, especially when the peroxidatic activity pattern is taken as a criterion.