Likewise, for leptospirosis, seven serum samples were positive (IgM+ IgG−) for the initial testing, one serum sample seroconverted from IgM+ IgG− to IgM− IgG+, with one serum sample remaining IgM− IgG+, confirming that IgG can remain in the bloodstream for a long time. Here, CD40LG is linked to leptospirosis.