Density gradient electrophoresis of mouse spleen lymphocytes: age-related differences. A critical thymus-dependent...

T and B BALB/c mouse spleen lymphocytes have been separated by preparative density gradient electrophoresis from animals of different ages. Significant age-related differences in the frequency of occurrence of cells exhibiting different mobility were observed in the young adult mouse. In the 6.5-week-old animals, the frequency of occurrence of the high (T lymphocytes) and low (B lymphocytes) mobility cells was changed, so that these lymphocytes exhibit an electrophoretic distribution profile different (essentially unimodal) from younger (3.5--5.5 weeks) or older (7.5--17 weeks) animals. In the latter two, bimodal electrophoretic distributions were observed. However, differences were also found in the frequency of occurrence of high and low mobility cells. The mobility distributions, representing individual cell types, were reproducible. Furthermore, the age-related changes were independent of the method of cell preparation and appeared in all mouse strains examined. Lymphocytes from animals thymectomized at the 5th week of age did not exhibit these changes (i.e. unimodal distribution) by the 6th week of age. Their electrophoretic distributions at the 6th week and thereafter were similar to those obtained from younger (3.5--5.5 weeks old) animals. It is concluded that the observed changes in the electrophoretic distributions of mouse spleen lymphocytes during development are thymus dependent and may be related to thymus involution.