Alternate sites of lymphopoiesis in the amphibian embryo.
Turpen Jb, Nicholas Cohen · PubMed · 1977
The presumptive ventral blood islands were reciprocally transplanted between chromosomally labelled 72-hour-old leopard frog embryos. At 10 days of development, the differentiating epithelial thymus glands were surgically removed. Following metamorphosis, the spleen and bone marrow from juvenile frogs were analysed cytophotometrically. During normal ontogeny, the vast majority of peripheral lymphocytes are derived from the thymus, not the ventral blood islands. In the absence of the thymus, the ventral blood islands made the major lymphocyte contribution to the peripheral lymphoid organs. Thus, removal of the thymus appears to initiate an alternate pathway of lymphocyte differentiation in the leopard frog.