| Abstract: | Cells carrying surface immunoglobulins (Ig+ cells) detected by the indirect immunofluorescence method, and cells forming rosettes with sheep's red blood cells (SRBC) with antibodies adsorbed on their surface and with complement (RFC), were found in the liver and spleen of rat fetuses at the 15th and 20th days of development. The relative percentage of Ig+ cells and RFC in the liver remained low and about the same level in rats on different days of postnatal development. In the spleen and bone marrow the number of Ig+ lymphocytes and RFC increased during the first month of the rat's life, to reach a maximum in animals aged 30 days, and fell sharply in old rats. No Ig+ cells or RFC were present in the thymus or they were found in very small numbers at certain times of investigation. Ig+ lymphocytes with  caps of fluorescence on their surface appeared in the spleen and bone marrow on the fifth and 10th days of life of the rat and their number rose considerably by the age of 30 days and in adult rats. No such cells were present in the lymphoid organs of old (40 months) animals.Laboratory of Embryonic Histogenesis, Institute of Human Morphology, Academy of Medical Sciences of the USSR. Institute of Molecular Biology, Academy of Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. P. Avtsyn.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 10, pp. 491–494, October, 1977. |
