title: Human immunoglobulin M memory B cells controlling Streptococcus pneumoniae infections are generated in the spleen.
abstract: Splenectomized and asplenic patients have a high incidence of infections by encapsulated bacteria and do not respond to polysaccharide vaccines. To understand whether the absence of the spleen is associated with a defined B cell defect, we analyzed B cell subsets in the peripheral blood. We found that a population of B cells known as immunoglobulin (Ig)M memory is lacking in patients without spleen. The absence of IgM memory B cells correlates with an impaired immune response to encapsulated bacteria not only in splenectomized patients, but also in individuals with an intact spleen. We show that the physiological and transient predisposition to pneumococcal infections of young children (0-2 yr) is associated with the lack of circulating IgM memory B cells and of serum antipolysaccharide IgM. We also demonstrate that IgM memory B cells are undetectable in a fraction of patients with common variable immunodeficiency, who have recurrent and invasive infections by encapsulated bacteria. IgM memory B cells, therefore, require the spleen for their generation and/or survival and are responsible for the protection against encapsulated bacteria.
authors.affiliation: Max-Plank Institute for Immunology, Department of Developmental Immunology, D-79108 Freiburg, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Kruetzmann
authors.forename: M Manuela
authors.initials: MM
authors.lastname: Rosado
authors.forename: Holger
authors.initials: H
authors.lastname: Weber
authors.forename: Ulrich
authors.initials: U
authors.lastname: Germing
authors.forename: Olivier
authors.initials: O
authors.lastname: Tournilhac
authors.forename: Hans-Hartmut
authors.initials: HH
authors.lastname: Peter
authors.forename: Reinhard
authors.initials: R
authors.lastname: Berner
authors.forename: Anke
authors.initials: A
authors.lastname: Peters
authors.forename: Thomas
authors.initials: T
authors.lastname: Boehm
authors.forename: Alessandro
authors.initials: A
authors.lastname: Plebani
authors.forename: Isabella
authors.initials: I
authors.lastname: Quinti
authors.forename: Rita
authors.initials: R
authors.lastname: Carsetti
mesh_terms: D000328:Adult; D000367:Age Factors; D001402:B-Lymphocytes / Q000276:immunology*; D018956:CD5 Antigens / Q000032:analysis; D017074:Common Variable Immunodeficiency / Q000276:immunology; D005260:Female; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis*; D007156:Immunologic Memory; D007223:Infant; D008875:Middle Aged; D011008:Pneumococcal Infections / Q000276:immunology*; D013154:Spleen / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000032:analysis
chemical_list: D018956:CD5 Antigens; D007075:Immunoglobulin M; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7