[Kintetics of lymph node reaction during humoral immunization. Ultrastructural autoradiographic study].

An ultrastructural autoradiographic analysis was done in order to study the kinetics of the lymph node cellular reactions during primary immunization of the mouse with heterologous red blood cells. A single injection of 3H-thymidine is given 24 hours or 48 hours after the antigen administration ; the animals are sacrified 2 to 48 hours later. The localisation of the labelled immunoblasts varies : they are first concentrated in the germinal centers to be dispersed later in the paracortical area and to infiltrate finally the medullar cords, where they change into plasma cells. These results suggest strongly the existence of an immunoblast migration from the cortex to the medulla.