CD40LG and COVID-19: To dissect the antibody component and specificity from the sera of COVID-19 clinically recovered patients, the magnitude of IgM, IgA, IgG, and IgG isotypes including IgG1 to IgG4 targeting RBD, S1, ECD, and NP were further analyzed by ELISA (Fig 4). Of note, barely detectable levels of anti-SARS-CoV-2 IgG2 and IgG4 were observed from all the patients in our cohort.