Objective To investigate the change of (NZB?NZW) F1 mice (BWF1) with ? 2 microglobulin deficiency and explore the role of ? 2 microglobulin in murine lupus.Methods ? 2 microglobulin knockout BWF1 mice were made according to the reference.The IgG type anti phospholipid antibodies.IgG type and anti dsDNA antibodies,rheumatoid factor,IgG and IgG3 were detected using ELISA.The survival rate,autoantibodies,IgG and IgG3 were compared between knockout mice (? 2m -/- ),wild type mice (? 2m +/+ ) and heterozygous mice (? 2m +/- ).Results ? 2m deficiency did not affect the survival rate of BWF1 mice.But the mortality of male BWF1 mice was lower than that of famale BWF1 mice.Antiphospholipid antibodies in ? 2m -/- BWF1 mice were lower than the wild type group and heterozygous group at month 4.Anti dsDNA antibodies had no difference between the three groups.RF was lower in ? 2m -/- BWF1 mice than ? 2m +/- and ? 2m +/+ BWF1 mice at month 4 and then elevated.At month 9 was higher than ? 2m +/- and ? 2m +/+ BWF1 mice significantly.As for the IgG,it was lower in ? 2m -/- BWF1 group than in ? 2m +/- and ? 2m +/+ BWF1 mice at months 4 and 6,and had no differnce between three groups.It minght be due to the severe proteinuria,ascites and hypoproteinemia.IgG3 was lower in ? 2m -/- BWF1 mice than in other groups,which only occur at month 6.Conclusion ? 2m knockout affects the murine lupus BWF1 in many ways,but not the survival rate.It affects the generation of autoantibodies mainly the antiphospholipid antibodies and RF.? 2m deficiency affects the function of neonatal FcR and results in IgG decreased because of difficult absorbent of IgG from gut and increased catabolism.