[Properties and kinetics of a population of B-lymphocytes during rat ontogenesis].

Cells bearing surface immunoglobulins (Ig+-cells) detected by the indirect immunofluorescent method and cells forming rosettes (RFC) with sheep erythrocytes coated with antibody and complement (EAC rosettes) were found in the liver and the spleen on the 15th and the 20th days of prenatal life of rats. The percentage of Ig+-cells and RFC in the liver was high and remained unchanged and at about the same level during the whole postnatal life. The spleen and the bone marrow displayed an increase of the Ig+-cells and RFC increased throughout the 1st month of postnatal life with the maximum at the 30th day after birth; a sharp decrease occurred in old animals. In the thymus the Ig+-cells and the RFC were either absent or present in very small amounts only at some periods of study. Ig+-cells with "capping" were discovered in the spleen and bone marrow on the 5th--10th days of postnatal life; their count increased considerably in 30-day and adult rats. Such cells were absent in the lymphoid tissues of old 40-month rats.