PDCD1 and Guillain-Barre syndrome: Others have hypothesized that T cells with deficient PD-1 signaling may be preferentially polarized toward effector T-cell differentiation and that the expressions of PD-1 and inducible T-cell co-stimulator may determine the immunological status of circulating memory Tfh cells in patients with GBS (Che et al., 2016; Schneiderbauer et al., 2017).