Relationship between temperature and apoptosis of human peripheral blood mononuclear cells

To examine the effect of various incubation temperatures on the apoptotic death of human peripheral blood mononuclear cells (PBMC), we incubated cells at 37degreesC, 22degreesC, and 4degreesC for 1 and 24 hours. In addition, cells incubated at 4degreesC for 3, 6, and 9 hours were rewarmed to 37degreesC until a total incubation time of 24 hours was reached. The percentage of apoptotic cells was detected by a flow cytometric assay using propidium iodide staining. Incubation of PBMC at the above-mentioned temperatures for 1 hour did not affect the percentage of apoptotic cells. However, incubation at 4degreesC for 24 hours resulted in the lowest percentage of apoptotic cells compared to those incubated at 22degreesC and 37degreesC. Rewarming of the cells to 37degreesC increased the percentage of apoptotic cells to a level similar to that of the controls (incubated at 37degreesC). Because PBMC are closely involved in the normal function of the immune system, the results of the study should be considered in cases in which these cells are exposed to various thermal conditions. (C)2003 The Japanese Society of Hematology.