Mitogenic Effect of Phytohaemagglutinin at Different Ages

Abstract

WHILE investigating the effect of myelotoxic drugs on the mitotic potential of phytohaemagglutinin-stimulated lymphocytes from peripheral blood, we found that the mitotic index (number of mitoses/1,000 cells) and percentage blast transformation was frequently lower in elderly individuals than in younger subjects. This report presents the results of standardized investigations of cell cultures, from 293 apparently healthy individuals ranging in age from 1 to 98 years after stimulation with phytohaemagglutinin. To avoid circadian influences all work was carried out at the same time of day, beginning with venipuncture at 9.00 a.m. To test the reproducibility of the method, duplicate cultures were made from the same individuals at the same time. The mean difference in mitotic index in duplicate cultures from ten subjects was 0.9 ± 4.4 (standard deviation). The mean difference in blast transformation of duplicate cultures was 5.1 ± 5.5 per cent. In seven subjects, ages 21–30 yr, cultures were repeated eight to thirty-five separate times during several weeks. The coefficient of variation (S.D./X.) for mitotic index (Fig. 1) in any given subject ranged from 25 per cent to 40 per cent. The value of mean ± 1 S.D. for mitotic index was the same for each individual so tested in this age group.