We analyzed the immunoreactivity against 15 strains from different species of the streptococcal genus using various sera from PBC patients and performed further assays using five strains of the Streptococcus anginosus group, the titers of which were higher than those of the other strains, and found that the PBC patient's sera had the highest IgM class titers to Streptococcus intermedius [20]. The gene discussed is CD40LG; the disease is primary biliary cholangitis.