title: Selective defect of anti-pneumococcal IgG in a patient with persistent polyclonal B cell lymphocytosis.
abstract: BACKGROUND
  Persistent polyclonal B cell lymphocytosis (PPBL) is a rare condition characterized by increased IgM and large excess of B cells with an IgD(+) CD27(+) phenotype. In normal individuals, these cells play a central role in the defense against pneumococcal infection. So far, few studies have characterized humoral immune responses in PPBL patients. We therefore measured IgG directed against S. pneumoniae antigens in a 51 yr-old woman with PPBL before and after vaccination with a pneumococcal 23-valent polysaccharide vaccine.
  
  
  METHODS
  Antibodies against pneumococcal antigens were measured first with an overall immunoassay using microplates coated with the 23-valent pneumococcal vaccine. A serotype-specific test was also performed according to the WHO consensus protocol.
  
  
  RESULTS
  Despite a large number of IgD(+) CD27(+) cells, our patient had low baseline titers of IgG directed against pneumococcal antigens and did not significantly respond to a 23-valent polysaccharide vaccine against S. pneumoniae. On the contrary, she had good titers of IgG directed against tetanus toxoid.
  
  
  CONCLUSIONS
  IgM(+) IgD(+) CD27(+) cells which accumulate in this patient with typical PPBL patient failed to perform IgG isotype switch after a polysaccharide vaccine. The potential mechanisms and relationships with the main features of PPBL are discussed. Further studies on a larger number of similar patients are needed.
authors.affiliation: Clinical Hematology, CHU Liège, Université de Liège, Liège, Belgium.
authors.forename: Kaoutar
authors.initials: K
authors.lastname: Hafraoui
authors.forename: Michel
authors.initials: M
authors.lastname: Moutschen
authors.forename: Julie
authors.initials: J
authors.lastname: Smet
authors.forename: Françoise
authors.initials: F
authors.lastname: Mascart
authors.forename: Nicole
authors.initials: N
authors.lastname: Schaaf-Lafontaine
authors.forename: Georges
authors.initials: G
authors.lastname: Fillet
mesh_terms: D000907:Antibodies, Bacterial / Q000276:immunology; D000918:Antibody Specificity; D001402:B-Lymphocytes / Q000276:immunology*; D000939:Epitopes; D005260:Female; D006801:Humans; D017578:Immunoglobulin Class Switching / Q000276:immunology; D007072:Immunoglobulin D / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D016130:Immunophenotyping; D008218:Lymphocytosis / Q000276:immunology* / Q000628:therapy; D008875:Middle Aged; D011008:Pneumococcal Infections / Q000276:immunology* / Q000628:therapy; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D013296:Streptococcus pneumoniae / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000939:Epitopes; D007072:Immunoglobulin D; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D022242:Pneumococcal Vaccines