Analysis of splenic lymphocytes with high electrophoretic mobility in adult and aged nude mice.

Electrophoretic mobility (EPM) and surface markers of splenic lymphocytes in adult (8 weeks old) and aged (over 1 year old) nude mice were investigated. Splenic lymphocytes in nude mice showed a bimodal pattern consisting of low mobility lymphocytes (LML) corresponding to B cells and high mobility lymphocytes (HML). The HML of nude mice showed the following immunological characteristics: (1) surface Ig- cells; (2) asialo GM1+ cells; (3) an increase in natural killer (NK) activity after depletion of B cells; (4) abrogation of the HML peak and NK activity after treatment with anti-asialo GM1 and complement. These findings suggested that HML in nude mice were NK cells. The mobility of NK cells was slightly lower than that of T cells in normal mice, although their histograms greatly overlapped each other. In the spleen cells of nude mice, there was a significant increase in the numbers of Thy-1+ cells and a decrease in the intensity of asialo GM1 antigen as a function of age. The surface markers of HML were Thy-1+- asialo GM1++ in adult nude mice, but were Thy-1+ asialo GM1+ in aged nude mice. However, although HML in aged nude mice became Thy-1+, these had almost the same EPM as those in adult nude mice.