Compared to non-COVID-19, COVID-19 patients displayed higher levels of RBD IgM (p = 0.0003) and IgG (p < 0.0001), but not IgA, in respiratory samples (Fig. 3a, b), which was possibly either due to technical issues or cross-reactivity of IgA antibodies (Fig. 3b top left panel). The gene discussed is CD40LG; the disease is COVID-19.