Bacterial transcytosis has previously been suggested to occur in CVID, as endotoxin in plasma and increased lipopolysaccharide have been identified, along with functional impairments of CD4 T cell proliferation, with increased programmed death 1 expression, as well as serum and plasma markers of systemic immune activation, sCD14 and sCD25 (31, 32, 33). Here, CD4 is linked to common variable immunodeficiency.