Correction of gld autoimmunity by co-infusion of normal bone marrow suggests that gld is a mutation of the Fas ligand gene.

lpr and gld mice develop phenotypically indistinguishable systemic autoimmune diseases and marked lymphadenopathy dominated by CD4-CD8- T cells. In vivo chimera experiments have demonstrated that both lpr T and lpr B cells are intrinsically defective. Analogous experiments were conducted using gld mice. Lethally irradiated gld mice were given mixtures of congenic gld and normal (+/+) bone marrow differentially marked by Ig heavy chain allotype. In sharp contrast to lpr-(+)/+ mixed chimeras, gld-(+)/+ chimeras had little autoantibody production at 5 months and minimal adenopathy at 6 months, indicating that the normal marrow-derived cells corrected the gld defect. Thus, aberrant autoantibody production is due to a defect extrinsic to the gld B cell and lymphoproliferation is due to a defect extrinsic to the gld T cell. These data support the hypothesis that gld mice lack an apoptosis-inducing ligand. The receptor for this ligand may be the Fas molecule, which is defective in lpr mice.