title: Unique characteristics of the intestinal immune system as an inductive site after antigen reencounter.
abstract: BACKGROUND
  Immunization prepares the body for a reencounter with the microbe. Information on the targeting of immune effector cells during secondary immune response--that is, lymphocyte homing--is scarce. In the present study, the homing potentials of lymphocytes are examined after antigen reencounter at mucosal versus nonmucosal sites.
  
  
  METHODS
  Orally or parenterally immunized volunteers were reimmunized orally or parenterally with Salmonella typhi Ty21a, and the expression of the gut homing receptor (HR), alpha(4)beta(7), and of the peripheral lymph node HR, L-selectin, was investigated in circulating antigen-specific antibody-secreting cells (ASCs). Lymphocytes were sorted by HR expression and examined for antibody production, by use of an enzyme-linked immunospot assay.
  
  
  RESULTS
  After oral reimmunization, 90% of ASCs were alpha(4)beta(7) positive and 88% were L-selectin positive, an expression profile that differed significantly from that found after oral primary immunization. After parenteral reimmunization, 45% of ASCs were alpha(4)beta(7) positive and 79% were L-selectin positive, similar to the results after parenteral primary immunization. The route of priming had no effect on HR patterns in either case.
  
  
  CONCLUSIONS
  Homing potentials of lymphocytes depend on the site of antigen reencounter. Whereas the HR profile after parenteral reimmunization resembles that after primary immunization, the profile after oral reimmunization is uniquely characterized by high expression of both HRs, suggesting gut-localized memory and effective homing ability to both the mucosal and systemic immune system. These data may prove valuable in the search for the most effective immunization route in humans.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Helsinki University Central Hospital, PL 348, FIN-00029 HUS, Finland. anu.kantele@hus.fi
authors.forename: Anu
authors.initials: A
authors.lastname: Kantele
authors.forename: Heikki
authors.initials: H
authors.lastname: Arvilommi
authors.forename: Katja
authors.initials: K
authors.lastname: Iikkanen
authors.forename: Erkki
authors.initials: E
authors.lastname: Savilahti
authors.forename: Helena P
authors.initials: HP
authors.lastname: Mäkelä
authors.forename: Christian
authors.initials: C
authors.lastname: Herzog
authors.forename: Emil
authors.initials: E
authors.lastname: Fürer
authors.forename: Jussi M
authors.initials: JM
authors.lastname: Kantele
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000921:Antibody-Producing Cells / Q000276:immunology*; D004333:Drug Administration Routes; D005260:Female; D006801:Humans; D007107:Immune System; D007263:Infusions, Parenteral; D007422:Intestines / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D016201:Receptors, Lymphocyte Homing; D012485:Salmonella typhi; D014436:Typhoid-Paratyphoid Vaccines / Q000008:administration & dosage / Q000276:immunology
chemical_list: D016201:Receptors, Lymphocyte Homing; D014436:Typhoid-Paratyphoid Vaccines