title: B cell-dependent T cell responses: IgM antibodies are required to elicit contact sensitivity.
abstract: Contact sensitivity (CS) is a classic example of in vivo T cell immunity in which skin sensitization with reactive hapten leads to immunized T cells, which are then recruited locally to mediate antigen-specific inflammation after subsequent skin challenge. We have previously shown that T cell recruitment in CS is triggered by local activation of complement, which generates C5a that triggers C5a receptors most likely on mast cells. Here, we show that B-1 cell-derived antihapten IgM antibodies generated within 1 day (d) of immunization combine with local challenge antigen to activate complement to recruit the T cells. These findings overturn three widely accepted immune response paradigms by showing that (a) specific IgM antibodies are required to initiate CS, which is a classical model of T cell immunity thought exclusively due to T cells, (b) CS priming induces production of specific IgM antibodies within 1 d, although primary antibody responses typically begin by day 4, and (c) B-1 cells produce the 1-d IgM response to CS priming, although these cells generally are thought to be nonresponsive to antigenic stimulation. Coupled with previous evidence, our findings indicate that the elicitation of CS is initiated by rapidly formed IgM antibodies. The IgM and challenge antigen likely form local complexes that activate complement, generating C5a, leading to local vascular activation to recruit the antigen-primed effector T cells that mediate the CS response.
authors.affiliation: Noda Institute for Scientific Research, Chiba-ken 278, Japan.
authors.forename: Ryohei F
authors.initials: RF
authors.lastname: Tsuji
authors.forename: Marian
authors.initials: M
authors.lastname: Szczepanik
authors.forename: Ivana
authors.initials: I
authors.lastname: Kawikova
authors.forename: Vipin
authors.initials: V
authors.lastname: Paliwal
authors.forename: Regis A
authors.initials: RA
authors.lastname: Campos
authors.forename: Atsuko
authors.initials: A
authors.lastname: Itakura
authors.forename: Moe
authors.initials: M
authors.lastname: Akahira-Azuma
authors.forename: Nicole
authors.initials: N
authors.lastname: Baumgarth
authors.forename: Leonore A
authors.initials: LA
authors.lastname: Herzenberg
authors.forename: Philip W
authors.initials: PW
authors.lastname: Askenase
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D002469:Cell Separation; D003182:Complement C5 / Q000276:immunology; D003877:Dermatitis, Contact / Q000276:immunology*; D005434:Flow Cytometry; D007075:Immunoglobulin M / Q000276:immunology*; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D003182:Complement C5; D007075:Immunoglobulin M