title: Luminal immunity in small-intestinal bacterial overgrowth and old age.
abstract: BACKGROUND
  The independent influences of small-intestinal bacterial overgrowth and old age on mucosal immunoglobulin production and secretion have not been assessed. This is an important issue, since luminal IgA deficiency may exacerbate small-intestinal bacterial overgrowth, the prevalence of which is high in selected elderly populations.
  
  
  METHODS
  Proximal small-intestinal aspirates were obtained from 33 subjects for bacteriologic analysis and measurement of total IgA, IgM, total IgG. IgG subclass, and IgD concentrations. IgA subclasses were measured in 24 unselected subjects. Serum immunoglobulin and salivary IgA concentrations were measured in all subjects.
  
  
  RESULTS
  IgA2 and IgG3 were predominant IgA and IgG subclasses in proximal small-intestinal luminal secretions. Luminal concentrations of IgA2 and IgM, but not IgG3 or any other IgG subclass, were significantly increased in small-intestinal bacterial overgrowth, which was present in 19 of 33 (57.6%) subjects. Old age did not influence these levels. Luminal immunoglobulin concentrations did not correlate significantly with either serum or salivary values. IgD was not measureable in proximal small-intestinal secretions.
  
  
  CONCLUSIONS
  Increased luminal concentrations of the secretory immunoglobulins, IgA2 and IgM, occur in small-intestinal bacterial overgrowth. Local investigation is mandatory when assessing the mucosal immunopathology of this disorder. Luminal IgG3 is unlikely to be predominantly derived from serum. Old age does not independently influence luminal immunity.
authors.affiliation: Dept. of Gastroenterology, Prince of Wales Hospital, University of New South Wales, Sydney, Australia.
authors.forename: S M
authors.initials: SM
authors.lastname: Riordan
authors.forename: C J
authors.initials: CJ
authors.lastname: McIver
authors.forename: D
authors.initials: D
authors.lastname: Wakefield
authors.forename: V M
authors.initials: VM
authors.lastname: Duncombe
authors.forename: T D
authors.initials: TD
authors.lastname: Bolin
authors.forename: M C
authors.initials: MC
authors.lastname: Thomas
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001424:Bacterial Infections / Q000276:immunology*; D016022:Case-Control Studies; D006801:Humans; D018928:Immunity, Mucosal / Q000276:immunology*; D007136:Immunoglobulins / Q000276:immunology* / Q000378:metabolism; D007410:Intestinal Diseases / Q000276:immunology* / Q000382:microbiology; D007413:Intestinal Mucosa / Q000276:immunology; D007421:Intestine, Small / Q000276:immunology / Q000382:microbiology; D008875:Middle Aged
chemical_list: D007136:Immunoglobulins