DNA synthesis in peritoneal lymphoid cells. Indirect induction of changes

Changes were observed in the DNA-synthesising cells of the murine peritoneal cavity after a single subcutaneous injection of (1) fluid thioglycollate medium, (2) guinea-pig serum, (3) pertussis vaccine, (4) fresh egg albumen, (5) bovine albumin Fraction 5, (6) normal saline as control. The subcutaneous route was chosen in order to avoid direct peritoneal irritation. A total of 180 animals was employed, in six groups of 30 each, and in each group five animals per day were examined for six days. In all cases except the controls there was a significant increase in the number of DNA-synthesising cells in the peritoneal fluid, as measured in autoradiographs following incubation with tritiated thymidine. The labelled cells were predominantly lymphoid, some resembling the transitional cells of bone marrow. There was also a smaller number of labelled macrophages. Changes were maximal after thioglycollate. The peak percentage of labelled cells occurred on Day 1 after thioglycollate and egg albumen, on Day 2 after guinea-pig serum, and on Day 4 after pertussis vaccine and bovine albumin.