Histochemical studies on fatty acid in lymphocyte-mediated immune reaction

Generation of fatty acids by cell-mediated immune reactions was demonstrated histochemically by Okamoto's method, which stains fatty acids and their alkaline earth salts red-brown. The red-brown deposits were observed more frequently on the mixed culture of immune lymph node cells of C3H/He and C57Bl/6 mice than on the culture of either of the pair alone. Similar evidence was observed in the reaction of immune lymph node cells with the corresponding allogeneic mouse tumour cells as well as on the immune lumphocytes of guinea-pig incubated in the presence of the soluble antigen PPD. In spite of the findings which indicated a possible generation of fatty acids in the immunological reaction of immune lymphocytes, we failed to demonstrate evidence of fatty acid generation in the ascites during rejection of allogeneic ascitic MM102 tumour cells, although accumulation of neutral lipid was evident. This unexpected contradicition was interpreted by finding that MM102 cells incubated with oleic acid did not contain fatty acid but did contain a remarkable amount of neutral lipid on histochemical examinations. This finding indicated that once generated, fatty acids would be converted to neutral lipid in the ascites where allogeneic tumour cells were rejected.