title: Role of IgM antibodies versus B cells in influenza virus-specific immunity.
abstract: We have compared the role of IgM antibodies with the role of B cells in control of primary influenza virus infection. Mice deficient in IgM (IgM(-/-)), but capable of producing other Igisotypes, exhibited increased pulmonary virus titers compared to wild-type mice. However, IgM(-/-) mice were less susceptible compared to B cell-deficient micro MT) mice. CD4(+) T cells from spleen and lung draining lymph nodes of infected micro MT mice showed reduced proliferation upon virus re-stimulation in vitro. Furthermore, numbers of IFN-gamma-producing CD4(+) effector T cells were reduced in the alveolar lavage (BAL) of micro MT mice but not IgM(-/-) mice. In contrast, total number of virus-specific CTL was almost comparable in BAL of micro MT and wild-type mice. Pulmonary recruitment of inflammatory macrophages and neutrophils occurred normally in both micro MT and IgM(-/-) mice. Interestingly, virus-specific IgG2a and IgG2b antibody responses were affected locally in the BAL and in the serum of IgM(-/-) mice, while IgG1 responses remained largely normal. Taken together, our data suggest a role for B cells to promote effector T cell responses and a role of both IgM and IgG antibodies in the defense against acute influenza virus infection.
authors.affiliation: Swiss Federal Institute of Technology Zurich, Molecular Biomedicine, Department of Environmental Sciences, Zürich-Schlieren, Switzerland.
authors.forename: Manfred
authors.initials: M
authors.lastname: Kopf
authors.forename: Frank
authors.initials: F
authors.lastname: Brombacher
authors.forename: Martin F
authors.initials: MF
authors.lastname: Bachmann
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001402:B-Lymphocytes / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology*; D008168:Lung / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D009975:Orthomyxoviridae / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M