When an apparently identical HL-A donor can be found and satisfactorily checked by the mixed lymphocyte reaction, it is worth attempting simple bone marrow grafting in a patient with combined immune deficiency syndrome who otherwise would die. Immunocompetence was given in this way to a baby girl by her 4-year-old brother and was confirmed by the presence of Y-chromosome in most of the transforming lymphocytes. IgA was late to emerge, presumably owing to the immaturity for IgA of the donor's bone marrow.
