The role of the thymus in development of lympho‐hemopoietic tissues. The effect of thymectomy on development of blood cells, bone‐marrow, spleen, and lymph nodes

Abstract

The effect of thymectomy at different ages in C3H mice on development of circulating leukocytes and cells of marrow, spleen and lymph nodes has been analyzed. Regardless of the age at which thymectomy is performed depression of numbers of circulating lymphocytes is produced. Tliymectomy at birth did not affect significantly the relative number of lymphocytes in the marrow during the first few weeks of life, later they fell to low levels. Thymectomy a t four weeks was followed by prompt reduction in relative numbers of lymphocytes in the marrow.After reaching six weeks of age, neonatally thymectomized mice showed a high proportion of monocytes in the marrow. Neonatal thymectomy and thymectomy at two weeks of age reduced the number of eosinophils in the marrow.Neonatal thymectomy inhibited development of lymphocytes in the spleen, whereas thymectomy later in life produced only transient depression of lymphocytes in this organ. In addition, neontal thymectomy decreased the relative numbers of small lymphocytes in the lymph nodes. This was associated with drastic depletion of lymphocytes in the deep cortical regions of the nodes.It has now been well established that thymectomy in the neonatal period in rodents, exerts a profound effect on development of lymphoid tissue and immunologic capacity (Archer and Pierce,

Effects of Irradiation, Anti-Thymocyte Serum and Corticosteroids on PHA and LPS Responsive Cells of the Mouse

“…2). Lymphocyte numbers in the thora cic duct and blood have been observed to decrease following adult thymectomy [21,27,28] and this may be reflected in the low er number of blood-borne PHA-responsive cells observed here. The results in figures 4b and 5b suggest that PHA responsiveness in spleen cells may also decrease by 7 weeks, but not before 3 weeks after the op eration.…”

Hematologic Standards for Healthy Newborn Thoroughbred Foals

“…It is now an accepted fact that the lymphocyte and its close relative, plasma cell, contain in the cytoplasm y-globulin and in the immunized animal, antibody [9,18,19].…”

“…The thymus plays the most important role in the development of lympho-hemopoietic tissue [9,19]. With age, and perhaps atrophy of the thymus, the circulating lymphocytes decrease again [11,19], No significant changes were noted in monocyte numbers during the studied period.…”