title: Intestinal B-cell isotype response in relation to local bacterial load: evidence for immunoglobulin A subclass adaptation.
abstract: OBJECTIVE
  In experimental animals, the indigenous microbiota modulates mucosal immunity. In humans, such direct evidence is scarce. The aim of this study was to examine the effect of intestinal bacteria on the local immunoglobulin (Ig) response.
  
  
  METHODS
  The numbers of IgA-, IgM-, and IgG-producing immunocytes per defined mucosal length unit were determined, and the local IgA subclass response was studied using immunohistochemistry in jejunal segments from adults with bacterial overgrowth and in sterile ileal urinary conduits from children.
  
  
  RESULTS
  The ileal bladder mucosa showed atrophy, but the number of immunocytes only tended to be decreased. The jejunal segments with bacterial overgrowth showed minor histological changes; the numbers of IgA and IgG immunocytes were fairly normal, whereas the number of IgM immunocytes was significantly reduced (P < 0.05) (12 cells/U) compared with control mucosa (24 cells/U). The number of IgA2 immunocytes was significantly decreased (P < 0.01) in ileal conduits (7 cells/U or 30% of total IgA) but increased (P < 0.05) in jejunal segments with bacterial overgrowth (42 cells/U or 43% of total IgA) compared with normal ileum (15 cells/U or 40% of total IgA) and jejunum (24 cells/U or 23% of total IgA).
  
  
  CONCLUSIONS
  An association exists between bacterial load and IgA subclass production. An increase in IgA2 may enhance mucosal protection and probably reflects immunomodulation caused by lipopolysaccharides.
authors.affiliation: Laboratory for Immunohistochemistry and Immunopathology, University of Oslo, Rikshospitalet, Norway.
authors.forename: K
authors.initials: K
authors.lastname: Kett
authors.forename: K
authors.initials: K
authors.lastname: Baklien
authors.forename: A
authors.initials: A
authors.lastname: Bakken
authors.forename: J G
authors.initials: JG
authors.lastname: Kral
authors.forename: O
authors.initials: O
authors.lastname: Fausa
authors.forename: P
authors.initials: P
authors.lastname: Brandtzaeg
mesh_terms: D000293:Adolescent; D000328:Adult; D001402:B-Lymphocytes / Q000276:immunology*; D001419:Bacteria / Q000254:growth & development*; D002648:Child; D006801:Humans; D007082:Ileum / Q000382:microbiology / Q000601:surgery; D007070:Immunoglobulin A / Q000096:biosynthesis* / Q000145:classification; D007074:Immunoglobulin G / Q000096:biosynthesis; D007132:Immunoglobulin Isotypes / Q000096:biosynthesis*; D007075:Immunoglobulin M / Q000096:biosynthesis; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology; D007422:Intestines / Q000276:immunology* / Q000382:microbiology; D007583:Jejunum / Q000276:immunology / Q000382:microbiology; D014547:Urinary Diversion
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D007075:Immunoglobulin M