CHMP5 and common variable immunodeficiency: When we analyzed SEB-induced cTfh and Tmem activation in anti-spike IgG-responsive and non-responsive CVID patients, only the IgG-nonresponders showed significantly reduced SEB-mediated activation of cTfh and Tmem as compared to healthy controls (Figure 5B), indicating that impaired anti-spike protein IgG response was associated with defective TCR-mediated CD4+ T cell activation.