CD40LG and sudden infant death syndrome: Similarly, infants dying of sudden infant death syndrome (SIDS) were found to have overstimulated tonsillar GCs reflected by an increased number of IgG+ and IgA+ PCs, probably caused by airway infection (83); and such activated B cells were apparently distributed in excessive numbers to regional secretory effector sites, including the parotid glands (84), thereby explaining the increased levels of salivary IgA and IgM in SIDS (85).