Ontogeny of the immune system in amphibians

Abstract

SYNOPSIS. Experiments with amphibians have revealed that tissues allografted in embryonic and early larval life may later succumb to a host immunological attack. In Xenopus, the ontogeny of this alloimmune response is correlated with the lymphoid maturation of the thymus. This article describes experiments primarily designed to ascertain if such a correlation exists in Rana pipiens.Initially, a histological study of the differentiation of the lymphomyeloid complex of the leopard frog was undertaken. At 18-21°C lymphoid histogenesis is well under way in the thymus and is beginning in many other organs during the third week of larval life. Extensive growth and differentiation of these organs follow. Observations are also presented on the structure, function and development of the lymphoid and Iymphomyeloid organs from late larval life throughmetamorphosis to adulthood.Experiments were then performed to determine the onset of the alloimmune response to embryonically transplanted neural fold material. At 18-21°C incompatibility phenomena, albeit slight, are first detected in these grafts as early as 17 days after fertilization, i.e. 15 days after transplantation. Thus, in the leopard frog, the alloimmune response develops soon after lymphoid maturation of the thymus. At later stages of development, a more vigorous response is witnessed, concomitant with a rapid phase of lymphoid organ differentiation. © 1971 by the American Society of Zoologists.