Somatic diversification in the absence of antigen-driven responses is the hallmark of the IgM+ IgD+ CD27+ B cell repertoire in infants.
T cell-dependent immune responses develop soon after birth, whereas it takes 2 yr for humans to develop T cell-independent responses. We used this dissociation to analyze the repertoire diversification of IgM(+)IgD(+)CD27(+) B cells (also known as "IgM memory" B cells), comparing these cells with switched B cells in children <2 yr of age, with the aim of determining whether these two subsets are developmentally related. We show that the repertoire of IgM(+)IgD(+)CD27(+) B cells in the spleen and blood displays no sign of antigen-driven activation and expansion on H-CDR3 spectratyping, despite the many antigenic challenges provided by childhood vaccinations. This repertoire differed markedly from those of switched B cells and splenic germinal center B cells, even at the early stage of differentiation associated with mu heavy chain expression. These data provide evidence for the developmental diversification of IgM(+)IgD(+)CD27(+) B cells, at least in very young children, outside of T cell-dependent and -independent immune responses.
Institut National de la Santé et de la Recherche Médicale U783, Développement du Système Immunitaire, Université Paris Descartes, Faculté de Médecine, Site Necker Enfants-Malades, Paris 75015, France.
Sandra
S
Weller
Maria
M
Mamani-Matsuda
Capucine
C
Picard
Corinne
C
Cordier
Damiana
D
Lecoeuche
Frédéric
F
Gauthier
Jean-Claude
JC
Weill
Claude-Agnès
CA
Reynaud
D015703:Antigens, CD / Q000276:immunology; D016175:B-Lymphocyte Subsets / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D015321:Gene Rearrangement; D014644:Genetic Variation; D006801:Humans; D007072:Immunoglobulin D / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology*; D007135:Immunoglobulin Variable Region / Q000235:genetics; D007148:Immunoglobulin mu-Chains / Q000276:immunology; D007156:Immunologic Memory; D007223:Infant; D008213:Lymphocyte Activation; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D014158:Transcription, Genetic; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000276:immunology*
D015703:Antigens, CD; D007072:Immunoglobulin D; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D007148:Immunoglobulin mu-Chains; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7