[Effect of hydrocortisone on the density-gradient distribution of autoreactive and 5'-nucleotidase-separating...

Rat thymocytes forming rosettes with autologous erythrocytes, are separated by centrifugation in the ficoll-verografin density gradient into two unequal fractions. A minor part of rosette forming cells is found in the gradient layers with the density of 1.069 and 1.073, a major part in the layers with the density of 1.090 and 1.080. After the administration of hydrocortisone to rats (2.5 mg per 100 g of mass) the number of rosette forming cells increased but in the gradient light fraction (d = 1.069). At 37 degrees C this thymocyte fraction separates the greatest amount of protein with 5'-nucleotidase activity. Under hydrocortisone influence the number of cells in this fraction and the amount of separable protein per 10(6) cells as well as 5'-nucleotidase activity per 10(6) increased in this fraction only. It has been assumed that an increase in 5'-nucleotidase separated at 37 degrees C, is a more constant feature of cortisone resistant thymocytes than a low affinity to autologous erythrocytes which is usually regarded as a feature of mature thymocytes.