title: CD27 expression in the human splenic marginal zone: the infant marginal zone is populated by naive B cells.
abstract: The splenic marginal zone of adult humans contains B cells, of which most express CD27, an antigen only recently identified as a marker for somatically mutated memory B cells. We investigated whether and to which extent the developing marginal zone in infants and children is populated by either memory (CD27+) or naive (CD27-) B cells. Frozen sections of 32 spleens of infants and children ranging in age from 6 days to 15 years and 6 adult spleens were investigated. The expression of CD27 in combination with monoclonal antibodies against CD3, CD21, IgM, IgD and ASM-1 was analyzed by immunohistochemistry. The marginal zone was already present at 4 months after birth but CD21 expression was observed first after 2 years. CD27-positive marginal zone B cells were observed firstly 2 years after birth and increased in number to adult levels at the age of 5 years. We demonstrated that the MZ of infants and young children is populated by naive B cells, which are replaced by memory B cells in a time frame of 2 to 5 years. Before the age of 2 years, although present, memory B cells appear to be unable to colonize the marginal zone. Because of the absence of memory B cells in the marginal zone, the immune system of a child is not capable to initiate a rapid secondary humoral immune response comparable to the adult immune response.
authors.affiliation: Department of Pathology and Laboratory Medicine, University Hospital Groningen, Groningen, The Netherlands. a.zandvoort@path.azg.nl
authors.forename: A
authors.initials: A
authors.lastname: Zandvoort
authors.forename: M E
authors.initials: ME
authors.lastname: Lodewijk
authors.forename: N K
authors.initials: NK
authors.lastname: de Boer
authors.forename: P M
authors.initials: PM
authors.lastname: Dammers
authors.forename: F G
authors.initials: FG
authors.lastname: Kroese
authors.forename: W
authors.initials: W
authors.lastname: Timens
mesh_terms: D000293:Adolescent; D000328:Adult; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology*; D002675:Child, Preschool; D015870:Gene Expression; D006801:Humans; D007156:Immunologic Memory; D007223:Infant; D007231:Infant, Newborn; D016131:Lymphocyte Subsets / Q000276:immunology; D017464:Receptors, Complement 3d / Q000032:analysis*; D013154:Spleen / Q000166:cytology* / Q000276:immunology*; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000032:analysis*
chemical_list: D017464:Receptors, Complement 3d; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7