Response of the Thymus and Immunologically Induced Lymphopenia.

Abstract
Administration of specific rabbit anti-rat lymphocyte gamma globulin (IgG) produced prolonged severe lymphopenia in rats made tolerant to normal rabbit IgG. A decrease in thymic weight due to the loss of small lymphocytes occurred. Combined morphologic and biochemical studies demonstrated marked proliferative activity of the precursor cells. The anti-lymphocyte IgG did not appear to gain entrance into the thymus.