FURTHER OBSERVATIONS ON POTENTIAL IMMUNOLOGICALLY COMPETENT CELLS OF FETAL LIVER ORIGIN

摘要

Using a modified graft-versus-host method, attempts were made to promote the maturation of potential immunologically competent cells of fetal liver origin (parental) in thymectomized F. hybrid hosts by means of irradiated and nonirradiated syngeneic (with respect to the fetal liver cells) and allergenic thymus grafts, suspensions of cells from syngeneic thymus, and syngeneic and allergenic thymus placed in diffusion chambers. It was found that, in this experimental model, only those thymus grafts which survived in the primary host for a prolonged period (i.e., syngeneic) and to which the fetal liver cells had direct physical access would promote the maturation of these lymphoid precursor cells. In addition it was noted that: (l) the method used had immunologic specificity;(2) viable fetal liver cells or thymus grafts were required in all experimental systems;(3) 18-20 day dissociated fetal thymus gave no evidence of the presence of either mature or immature lymphoid cells;and (4) potential immunologically competent cells appeared to be incapable of producing hem agglutinins to rat erythrocytes or of rejecting allergenic or xenogeneic skin grafts in the absence of the host thymus.