title: Interleukin-5 plays a key role in mouse strain- dependent susceptibility to contact hypersensitivity through its effects on initiator B cells.
abstract: BACKGROUND
  Elicitation of contact hypersensitivity requires antigen-specific immunoglobulin M (IgM) antibodies that trigger recruitment of effector T cells to the local tissue. These antigen-specific IgM antibodies are produced by B-1-like 'initiator B cells'. In this study, we compared susceptibility to hapten-induced contact hypersensitivity between BALB/c and C57BL/6 mice.
  
  
  METHODS
  BALB/c and C57BL/6 mice were sensitized by painting oxazolone onto the skin and were challenged on the ears with the same hapten on day 4. Ear thickness and serum hapten-specific IgM levels were measured at 24 h post-challenge. Peritoneal cells were harvested and the numbers of B cell subpopulations were counted. Interleukin (IL)-5 was intraperitoneally injected into BALB/c and C57BL/6 mice, and the change in numbers of B cell subpopulations and serum IgM levels was monitored.
  
  
  RESULTS
  Oxazolone induced stronger ear swelling and specific IgM responses in BALB/c mice than in C57BL/6 mice. BALB/c mice had higher numbers of peritoneal B-1 cells than C57BL/6 mice at steady state. IL-5 injection increased the number of peritoneal B-1 cells and serum IgM levels more significantly in BALB/ mice than in C57BL/6 mice.
  
  
  CONCLUSIONS
  BALB/c mice exhibit higher susceptibility to hapten-induced contact hypersensitivity than C57BL/6 mice, most likely because they have a higher number of B-1 cells, leading to massive production of hapten-specific IgM antibodies upon contact sensitization. The differences in the number of B-1 cells and IgM responses between the two strains of mice may be attributed to the difference in responsiveness of B-1 cells to IL-5.
authors.affiliation: Faculty of Pharmacy, Iwaki Meisei University, Iwaki, Japan. atsukof @ hama-med.ac.jp
authors.forename: Atsuko
authors.initials: A
authors.lastname: Itakura
authors.forename: Masashi
authors.initials: M
authors.lastname: Ikutani
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Takatsu
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kikuchi
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology; D016175:B-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D003877:Dermatitis, Contact / Q000276:immunology* / Q000378:metabolism; D004198:Disease Susceptibility; D005260:Female; D007075:Immunoglobulin M / Q000097:blood / Q000276:immunology; D015848:Interleukin-5 / Q000378:metabolism*; D053666:Interleukin-5 Receptor alpha Subunit / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010529:Peritoneal Cavity
chemical_list: D000941:Antigens; D007075:Immunoglobulin M; D015848:Interleukin-5; D053666:Interleukin-5 Receptor alpha Subunit