Compared to patients with PBC alone, PBC-SLE patients had lower γ-glutamyl transpeptidase (γ-GGT) and immunoglobulin M (IgM) levels, suggesting that presence of SLE in PBC patients appeared to be associated with significantly less extensive liver damage and SLE might protect against progression of PBC by delaying cirrhosis and the need for liver transplantation; PBC-RA patients had higher serum immunoglobulin G (IgG) and alkaline phosphatase (ALP) levels, suggesting that presence of RA might be a harmful factor in the prognosis of PBC. The gene discussed is CD40LG; the disease is systemic lupus erythematosus.