William J. Murphy

Immunobiology of Bone Marrow Transplantation: Studies Using Scid Mice

Natural killer (NK) cells are believed to be an effector cell capable of mediating bone marrow allograft rejection in lethally irradiated recipients. However, despite a large body of experimental evidence that suggests that NK cells can mediate specific marrow allograft rejection, the nature of the proposed target antigen present on the marrow stem cell and the mechanism by which NK cells can detect disparities has remained an enigma. NK cells are believed to recognize hematopoietic histocompatability (Hh-1 or Hh) antigens present on incompatible stem cells. Hh antigens are expressed in a noncodominant manner in which homozygosity at the MHC (H-2 in the mouse) is a prerequisite for the expression of Hh antigens (Bennett 1972). In other words, H-2 homozygous marrow grafts are resisted and H-2 heterozygous grafts proliferate. Hh antigens have proven to be elusive to isolate and characterize. However, through the analysis of the rejection patterns using recombinant mouse strains they have been shown to be distinct from class I MHC genes, and are encoded for by genes between the S and D locus of H-2 (Rembecki et al. 1988).