The occurrence of DNA synthesis in mouse peritoneal macrophages was estimated autoradiographically in cells cultured on glass in the presence of tritiated thymidine. Subcutaneous injection of a soluble antigen, human serum albumin (HSA) into mice previously immunized with HSA in Freund’s complete adjuvant was followed, after a lag of at least 16 h, by the onset of DNA synthesis in peritoneal macrophages. This effect was immunologically specific and was accompanied by morphological changes indicating activation. The ability to respond in this way was passively transferable by means of spleen cells, but not serum, from immunized mice. DNA synthesis in macrophages was induced in vivo by Concanavalin A, phytohaemagglutinin-P, anti-lymphocyte globulin, bacterial endotoxin and normal mouse serum. The number of macrophages synthesizing DNA was also increased in mice with graft-versus-host reactions and in mice bearing a syngeneic methylcholanthrene-induced tumour.

Summary Phytohaemagglutinin‐induced transformation of normal human lymphocytes was lower, as assessed by tritiated thymidine incorporation, in sera from patients with chronic renal failure than in normal sera. Transformation was lower in normal sera dialysed against tissue culture medium and lower still in patients’ sera similarly dialysed. Addition of patients’ sera, untreated or dialysed, to cultures of normal cells in normal serum depressed lymphocyte transformation.

No abstract

Subcutaneous injection of ovalbumin (OA) into mice immunized with OA in Freund’s complete adjuvant was followed by an increase in the numbers of peritoneal macrophages synthesizing DNA, determined by autoradiography. The effect was immunologically specific. The increase was followed by an increase in the numbers of peritoneal macrophages; the numbers of peritoneal lymphocytes also increased. Injection of OA into immunized or normal mice was followed by a blood monocytosis. Increased DNA synthesis, determined by liquid scintillation counting, occurred in spleen or lymph node cells from immunized mice, cultured with OA. Diluted supernatants from such cultures, injected intravenously into normal mice, caused increases in the numbers of DNA-synthesizing peritoneal macrophages. Similarly, supernatants from concanavalin A stimulated spleen cells, freed of Con A, also caused an increase in DNA-synthesizing macrophages.