Immunocompetence of Spleen Cells From Neonatally Thymectomized Mice Conferred in Vitro by a Syngeneic Thymus Extract

Abstract

Impaired immunological competence of spleen cells from neonatally thymectomized C57B1/6 young adult mice was apparent when these cells were tested in an in vitro graft-versus-host assay. Spleen cell inocula prepared from thymectomized mice did not induce enlargement of (C3H/eb x C57BI/6)F1 newborn spleen explants, whereas the same number of cells from intact donors consistently initiated splenomegaly. Spleen enlargement was observed, however, when the explants were challenged by cells from thymectomized donors in the presence of syngeneic thymus extract, indicating that the spleen cells in suspension attained immunological competence under the influence of a non-cellular component of the thymus. Immunocompetence was also evident when the cells from thymectomized donors were first incubated with thymus extract for 1 hr and subsequently tested for reactivity. Cells from the same thymectomized donor mice exposed in parallel to extracts from syngeneic spleen or mesenteric lymph node at an equivalent protein concentration did not initiate a graft-versus-host response. These experiments demonstrate that immune reactivity in the graft-versus-host response involves activation of lymphoid cells by a humoral factor of the thymus acting directly upon these cells.

Increased Incidence of Urethane Induced Lung Adenomata by Autosensitized Lymphocytes

“…We found previously that immunological impairment of the host as a result of neonatal thymectomy (Trainin et at., 1967), or ALS treatment (Trainin and Linker-Israeli, 1970) was associated with an increase in the yield of lung adenomata.…”

“…We have reported previously that an impairment of thymus function was followed by a higher carcinogenic response to urethane in mice (Trainin et al, 1967;Trainin and Linker-Israeli, 1970). The effects of the injection of autosensitized lymphocytes upon the T cell competence of the recipients in our experiments was examined.…”

“…The calculated area of each test spleen fragment divided by the corresponding area of its paired reference fragment provided a numerical index of splenomegaly. Cultures were considered reactive when the index of splenomegaly obtained was 1-2 or more (Trainin, Small and Globerson, 1969).…”

Some Endocrine Aspects of the Thymus Gland

“…The extract from syngeneic or allogeneic mice restored the ability of thymectomized mice to reject skin grafts . Trainin et al (1969) (Robey, 1973). Thymosin was found to accelerate the development of immunocompetence in spleen cells in normal, neonatal mice after injection of the extract on days 1 and 2 after birth.…”

Amplification of the proliferative response to alloantigen by a factor present in an extract of syngeneic thymic lymphoid cells.

“…Cohen et al (40) reported that the addition of thymosin to one-way MLCs resulted in an increase in the proliferative response of thymus cells but a decrease in the response of spleen cells to alloantigen. Another thymus product, thymus humoral factor, is also assumed to be a product of the reticuloepithelial cells of the thymic medulla, although its cellular origin is less well-defined than in the case of the factors discussed above (41)(42)(43). Thymus humoral factor has been observed to either increase or decrease MLC reactivity, depending upon the assay conditions utilized.…”