CD40LG and cytomegalovirus infection: The percentage of CMV-IgM+ participants was also significantly greater in IIM patients than in healthy controls (8.3% vs. 0%, p = 0.05) as was the percentage of CMV-IgG+ participants (99.5% vs. 93.9%, p = 0.024), suggesting that CMV infection was a predisposing factor in the IIM group.