Mice with SCID disease have previously been successfully engrafted with human peripheral blood mononuclear cells (PBMC) obtained from normal individuals and from patients with various diseases. To determine whether SCID mice engrafted with SLE PBMC produced autoantibodies with specificities similar to those in the SLE donor, and to investigate which variables influence autoantibody production in the SCID recipients, we injected PBMC from 16 SLE patients into SCID mice and tested the recipients for autoantibodies to DNA and to five recombinant autoantigens. Ten out of 16 (68%) lupus and six out of nine (67%) normal grafts were successful as determined by the presence of human IgG greater than or equal to 5 micrograms/ml of SCID serum post-transfer. Autoantibodies to La/SSB, Ro/SSA, and RNP were detected in five out of 10 SCID-SLE recipients by ELISA and immunoblotting up to 22 weeks post-engraftment. The detection of autoantibodies in SCID-SLE mice was more closely related to autoantibody levels in donor sera than to total IgG concentrations in the SCID recipients. Autoantibody activity/mg IgG was similar in the donor and recipient sera. Histological evaluation of eight SCID-SLE mice killed 4-22 weeks post-transfer revealed population of the SCID thymus and spleen with mononuclear cells, but no evidence of lupus nephritis or dermatitis. These findings indicate that SCID mice can be engrafted with PBMC from patients with lupus and that specific autoantibodies are produced up to 5 months post-transfer. Failure to develop glomerulonephritis may be explained by low or absent anti-DNA antibodies or by changes in the cellular composition of the PBMC grafts.