CD40LG and erythema multiforme: For the patients, who were tested by IgM ELISA, IgG ELISA, and WB (the patients with arthritis or EM-like lesions), four mutually exclusive groups were identified: tested positive by WB regardless of IgG or IgM ELISA results; tested positive by IgM or IgG ELISA but negative by WB; tested negative by IgM ELISA, IgG ELISA and WB and others (Table 1).