We observed a correlation between proportions of activated ICOS+PD1+ cTfh cells and levels of IgG Abs binding to SARS-CoV-2 S antigen in ALS as well as in plasma, supporting that cTfh cells are an interesting and easily accessible biomarker for GC B cell responses even very early during a response. This evidence concerns the gene ICOS and amyotrophic lateral sclerosis.