Age-dependent development of the splenic marginal zone in human infants is associated with different causes of death.

Infants are more susceptible to infections caused by T cell- independent type 2 (TI-2) polysaccharide antigens of certain encapsulated bacteria. Immune responses against this type of antigen are related to the splenic marginal zone (MZ). However, only few data exist on the age-dependent developmental stages of the human spleen in early childhood and on their association with different diseases. Therefore, the present study aimed to investigate spleens of a large number of children at very young ages (12 days to 32 months), derived from autopsy cases. Immunohistochemical labeling was performed on paraffin sections of 34 spleens using a panel of monoclonal antibodies. The shape and size of the white pulp compartments were examined and correlated to the cause of death of the children. Results show that the development of the different compartments was statistically age-dependent, but no clear-cut time point for the maturity of each compartment was seen. Furthermore, the MZ was significantly more often missing when sudden infant death (SID) and/or infection were the cause of death, compared with other violent or traumatic reasons that served as controls. This association supports the concept that an immature state of the spleen and especially of the MZ might contribute to the increased susceptibility to bacterial infections in young infants.