CD40LG and COVID-19: Subsequently, fresh finger-prick blood was taken from each participant and placed directly into the well of the QuickZen COVID-19 IgM/IgG kit (ZenTech, Angleur, Belgium), an immune colloidal gold lateral flow test kit that detects IgM and IgG against SARS-CoV-2 S-RBD (receptor-binding domain of the S protein of SARS-CoV-2).