IL2 and infection: This timing was selected, taking into consideration recent data on the production of neutralizing antibodies at 39 days after infection [16,17], to discriminate between the reported half-life of IgG, being less than 30 days [18], and the presence of memory B cells and plasma cells, detected as early as 7 days after primary immunization [19], even in the absence of stimulatory factors (such as R848 and IL-2), as already reported for viral antigens [5].