“…These patients had small numbers of memory B cells (CD19 + /CD27 + ), very large numbers of naive (CD19 + /CD27 − ) and immature (CD19 + /CD21 − ) B cells, and an impaired Ig class switch ( Kuehn et al, 2013 ; Belot et al, 2013 ). High counts of circulating CD8 + T cells and double-negative (CD4 − /CD8 − ) T cells were observed in some cases, together with slightly low levels of T cell proliferation in vitro ( Kuehn et al, 2013 ; Sharifinejad et al, 2020 ; Kiykim et al, 2015 ). Intriguingly, these patients suffer not only from autoimmune disease, but also from recurrent and/or severe infections ( Kuehn et al, 2013 ; Belot et al, 2013 ; Kiykim et al, 2015 ; Salzer et al, 2013 ; Lei et al, 2018 ; Nanthapisal et al, 2017 ; Meyts et al, 2021 ; Sharifinejad et al, 2020 ).…”