Differentiation of T-cell Precursors in Nude Mice Demonstrated by Immunofluorescence of T-cell Membrane Markers

When the thymus from an AKR mouse (TL(-), theta-AKR) is grafted to a BALB/c-nu/nu mouse (TL2, theta-C3H), the grafted thymus is rapidly repopulated by host lymphocytes, i.e., lymphocytes having the TL2 and theta-C3H T-lymphocyte membrane antigen markers. theta-C3H lymphocytes also appear rapidly in the spleen and lymph nodes. After a few weeks, BALB/c nude mice grafted with AKR thymus and normal BALB/c mice could not be distinguished on the basis of the number of TL-positive thymocytes or theta-C3H-positive lymphocytes in thymus, spleen, or lymph nodes. These experiments give a definitive proof of the existence of precursor cells for the T compartment of the lymphoid system in the nude mouse. They strongly suggest the involvement of host-derived T cells in the recovery of some T-cell functions by nude mice grafted with allogeneic thymuses.