Briefly, individual paired serum samples (n = 36) at the onset (MAT-negative, leptospirosis false-negatives) and in the convalescent phase (MAT-positive), and additional unpaired MAT-positive serum samples (n = 142) were incubated with immobilized rChi2, followed by incubation with HRP-conjugated anti-human IgG and IgM (1:10,000 of each antibody). Here, CD40LG is linked to leptospirosis.