Development of immunocompetent lymphocytes in vivo from murine umbilical cord blood cells

Reports concerning the immunological functions of lymphocytes derived from umbilical cord blood cell (UCBC) have been limited. In murine syngeneic transplantation system using green fluorescent protein transgenic donors, UCBC-derived lymphocytes were studied for their immunological competence. Hematopoietic stem cells (HSC) among UCBC differentiated in the recipients into phenotypically mature T and B lymphocytes. The T lymphocytes were capable of specific recognition of major histocompatibility complex/peptide complex and of the subsequent activation. The antigen-induced CD4(+) T cells produced lymphokine upon in vitro antigen stimulation. CD8(+) T cells simulated in the mixed lymphocyte culture could lyze specific target cells. Furthermore, RAG2(-/-) mice reconstituted with UCBC mounted specific antibody responses to T-dependent antigen comparable to those by bone marrow chimeras and also rejected allogeneic skin grafts. Collectively the data indicated that T and B lymphocytes derived from UCBC-HSC are fully competent in immunological terms.