Contribution of a thymic humoral factor to the development of an immunologically competent population from cells of mouse bone marrow.

The hypothesis that cells located in mouse bone marrow can acquire immunological competence by a process that involves interaction with a noncellular component of the thymus was tested using an in vitro assay of graft-versus-host reactivity as a criterion of cell competence. When suspensions of C57BL bone marrow cells were incubated in thymus extract and injected into mice incapable of inducing a response in the graft-versus-host assay as a result of neonatal thymectomy, or adult thymectomy plus irradiation, or because of genetic similarity with the (C3H x C57BL)F(1) tissue used for challenge in the assay, competent cells were recovered from the spleens of the injected mice. The reactive cells were shown to be of bone marrow origin since immune reactivity was related to the genetic makeup of the bone marrow cells rather than that of the intermediate recipients.

Studies on some physicochemical properties of a thymus humoral factor conferring immunocompetence on lymphoid cells.

By means of an assay of graft-versus-host activity some properties of the thymic humoral factor which confers immunocompetence upon lymphoid cells in vitro have been studied. Allogeneic and xenogeneic thymic preparations were found to activate lymphoid cells from neonatally thymectomized mice, enabling initiation of a graft-versus-host response. Thus, this thymus factor is apparently neither strain nor species specific.

Some biochemical effects of triamcinolone acetonide on rat liver and muscle.

1. The powerful anti-inflammatory glucocorticoid triamcinolone acetonide, administered to rats at 20 and 2.5mg/kg, leads to a decrease in the incorporation in vivo of [(3)H]uridine and [(32)P]orthophosphate into hind-limb skeletal muscle.

Immunocompetence of spleen cells from neonatally thymectomized mice conferred in vitro by a syngeneic thymus extract.

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)F(1) 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.