Heparin-induced hyperplasia of lymphoid tissue.

Experiments on newborn and sexually mature mice and rats showed that repeated injection of heparin leads to an increase both in the number of lymphocytes in the thymus and spleen and in the number of hematopoietic stem cells forming endogenous colonies in the spleen. The lymphoid tissue and the pool of colony-forming units are conjecturally under the regulatory influence of the adrenocortical hormones and of the product of the mast cells-heparin.