Intriguingly, beyond absence of IgA, the lack of IL-10 producing regulatory B cells in CVID may play a role in susceptibility to Giardia—recently, investigators developed an IL-10 deficient mouse model that showed intractable diarrhea, lethargy and weight loss following infection with Giardia muris in mice lacking IL-10 while wild type mice did not showcase any evidence of infection (33, 34). Here, IL10 is linked to common variable immunodeficiency.