ABSTRACT
BACKGROUND: Toll-like receptors contribute to the establishment of adaptive immune responses. OBJECTIVE: The reported studies were conducted to examine the effects of the Toll-like receptor (TLR)-7 ligand, resiquimod, on human naive B-cell differentiation. METHODS: Naive human B cells were cultured with resiquimod in the presence or absence of IL-2 and IL-10. Secreted IgM and IgG were measured by ELISA, and IL-6, IL-10, and IFN-alpha were measured by a multiplex protein array. Cell proliferation was assessed by measuring [(3)H]thymidine uptake. mRNA for activation-induced cytidine deaminase and I(gamma 1)-C(mu) circle transcripts was measured by means of RT-PCR. RESULTS: Resiquimod induced the production of IgM and, to a lesser extent, IgG by naive human B cells in association with the secretion of IL-6 and IL-10, and a weak proliferative response. IL-2 and IL-10 synergized with resiquimod in markedly augmenting resiquimod-induced IgM and IgG production and proliferation. Resiquimod also stimulated production of IgG by B cells isolated from the blood of a patient with the X-linked hyper-IgM syndrome, with a greater response when these cells were costimulated with IL-2 and IL-10. The stimulated naive B cells from healthy volunteers displayed molecular evidence of immunoglobulin class-switch recombination-namely the appearance of activation-induced cytidine deaminase and I(gamma 1)-C(mu) circle transcripts. CONCLUSION: Perturbation of TLR-7 on naive human B cells can lead to the induction of immunoglobulin class switch and IgG production in the absence of B-cell receptor cross-linking and CD40-CD40L interaction. The results are relevant to vaccine development and mechanisms by which microbial infection may lead to autoimmunity.
Subject(s)
Antibody Formation/immunology , B-Lymphocytes/immunology , Imidazoles/pharmacology , Immunoglobulin G/immunology , Immunoglobulin M/immunology , Toll-Like Receptor 7/immunology , Adult , Antibody Formation/drug effects , Antibody Formation/genetics , CD40 Antigens/genetics , CD40 Antigens/immunology , CD40 Ligand/genetics , CD40 Ligand/immunology , Cell Proliferation/drug effects , Cells, Cultured , Drug Synergism , Female , Gene Rearrangement, B-Lymphocyte/drug effects , Gene Rearrangement, B-Lymphocyte/genetics , Gene Rearrangement, B-Lymphocyte/immunology , Humans , Hyper-IgM Immunodeficiency Syndrome, Type 1/genetics , Hyper-IgM Immunodeficiency Syndrome, Type 1/immunology , Imidazoles/immunology , Immunoglobulin G/genetics , Immunoglobulin M/genetics , Interferon-alpha/genetics , Interferon-alpha/immunology , Interleukin-10/immunology , Interleukin-10/pharmacology , Interleukin-2/immunology , Interleukin-2/pharmacology , Interleukin-6/genetics , Interleukin-6/immunology , Ligands , Male , Middle Aged , Receptors, Antigen, B-Cell/genetics , Receptors, Antigen, B-Cell/immunology , Toll-Like Receptor 7/agonists , Toll-Like Receptor 7/geneticsABSTRACT
The thymus is thought to play an important role in the pathogenesis of myasthenia gravis (MG), an autoimmune disease characterized by skeletal muscle weakness. However, its role remains a mystery. The studies described represent our efforts to determine how intrathymic expression of the neuromuscular type of acetylcholine receptors (nAChRs) is involved in the immunopathogenesis of MG. We review our work characterizing the expression of the alpha subunit of nAChR (nAChRalpha) in the thymus and advance a new hypothesis that examines the intrathymic expression of this autoantigen in disease pathogenesis.
Subject(s)
Myasthenia Gravis/etiology , Receptors, Cholinergic/biosynthesis , Thymus Gland/metabolism , Animals , Cytokines/pharmacology , Disease Models, Animal , Gene Expression Regulation/drug effects , Humans , Inflammation/virology , Leukemia Virus, Murine/pathogenicity , Mice , Muscle, Skeletal/metabolism , Myasthenia Gravis/complications , Myasthenia Gravis/immunology , Protein Isoforms/biosynthesis , Protein Isoforms/genetics , Receptors, Cholinergic/genetics , Thymoma/complications , Thymoma/immunologyABSTRACT
The thymus has been considered to play an important role in the pathogenesis of myasthenia gravis (MG), an autoimmune disease characterized by skeletal muscle weakness. However, the pathogenic role of the thymus still remains a mystery. The neuromuscular type of acetylcholine receptor (AChR) was the first self-protein associated with a defined autoimmune disease that was found to be expressed by thymic stromal populations. The studies described herein represent our efforts to determine how this "promiscuous" autoantigen expression may be involved in the immunopathogenesis of MG. We review our work, characterizating the expression of the alpha subunit of AChR (AChRalpha) in the thymus, and advance a new hypothesis that examines the intrathymic expression of this autoantigen in disease pathogenesis.