CD40LG and systemic lupus erythematosus: By comparing the serum levels of IgG and IgM autoantibody isotypes in the subgroups of healthy controls (HCs), ILE, and SLE, they found that patients in SLE group exhibited increased level of IgG autoantibodies compared with ILE, whereas alterations in IgM autoantibodies showed the opposite trends: high in ILE but low in SLE, implying that there might be a class switch from IgG to IgM during the transition from ILE to SLE [23].