 This suggested that the thymus produces substances important in the development of immunity.It was not until 1971 that it was discovered that thymus-derived lymphocytes (T-cells) were important regulators of bone-marrow-derived antibody-producing lymphocytes (B-cells).After the discovery that the thymus was producing profound regulatory factors, several groups of scientists began trying to extract and purify this factor from thymus glands in much the same manner that insulin was prepared from the pancreas for therapeutic use in diabetes.