CDR1
Cerebellar degeneration-related antigen 1 (CDR34)
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The escape of anti-self B cells from tolerance mechanisms like clonal deletion, receptor editing, and anergy results in the production of autoantibodies, which is a hallmark of many autoimmune disorders. In this study, we demonstrate that both germline sequences and somatic mutations contribute to autospecificity of B cell clones. For this issue, we investigated the development of antinuclear autoantibodies (ANAs) and their repertoire in two different mouse models. First, in aging mice that were shown to gain several autoimmune features over time including ANAs. Second, in mice undergoing a chronic graft-versus-host disease (GVHD), thereby developing systemic lupus erythematosus-like symptoms. Detailed repertoire analysis revealed that somatic hypermutations (SHM) were present in all Vh and practically all Vl regions of ANAs generated in these two models. The ANA B cell repertoire in aging mice was restricted, dominated by clonally related Vh1-26/Vk4-74 antibodies. In the collection of GVHD-derived ANAs, the repertoire was less restricted, but the usage of the Vh1-26/Vk4-74 combination was still apparent. Germline conversion showed that the SHM in the 4-74 light chain are deterministic for autoreactivity. Detailed analysis revealed that antinuclear reactivity of these antibodies could be induced by a single amino acid substitution in the CDR1 of the Vk4-74. In both aging B6 and young GVHD mice, conversion of the somatic mutations in the Vh and Vl regions of non Vh1-26/Vk4-74 using antibodies showed that B cells with a germline-encoded V gene could also contribute to the ANA-reactive B cell repertoire. These findings indicate that two distinct pathways generate ANA-producing B cells in both model systems. In one pathway, they are generated by Vh1-26/Vk4-74 expressing B cells in the course of immune responses to an antigen that is neither a nuclear antigen nor any other self-antigen. In the other pathway, ANA-producing B cells are derived from progenitors in the bone marrow that express B cell receptors (BCRs), which bind to nuclear antigens and that escape tolerance induction, possibly as a result of crosslinking of their BCRs by multivalent determinants of nuclear antigens.
MeSH Terms
- Aging
- Amino Acid Substitution
- Animals
- Antibodies, Antinuclear
- Antibodies, Monoclonal
- Antigens, Nuclear
- Autoimmunity
- B-Lymphocytes
- Graft vs Host Disease
- Histones
- Immune Tolerance
- Immunoglobulin Heavy Chains
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Mutation
- Receptors, Antigen, B-Cell
Keywords
- antinuclear antibodies
- autoantibodies
- monoclonal antibodies
- mouse model
- somatic hypermutation
- systemic lupus erythematosus-like disease
Alzheimer's disease (AD) is a primary and progressive neurodegenerative disorder, which is marked by cognitive deterioration and memory impairment. Atrophy of hippocampus and other basal brain regions is one of the most predominant structural imaging findings related to AD. Most studies have evaluated the pre-clinical and initial stages of AD through clinical trials using Magnetic Resonance Imaging. Structural biomarkers for advanced AD stages have not been evaluated yet, being considered only hypothetically. To evaluate the brain morphometry of AD patients at all disease stages, identifying the structural neuro-degeneration profile associated with AD severity. AD patients aged 60 years or over at different AD stages were recruited and grouped into three groups following the Clinical Dementia Rating (CDR) score: CDR1 (n = 16), CDR2 (n = 15), CDR3 (n = 13). Age paired healthy volunteers (n = 16) were also recruited (control group). Brain images were acquired on a 3T magnetic resonance scanner using a conventional Gradient eco 3D T1-w sequence without contrast injection. Volumetric quantitative data and cortical thickness were obtained by automatic segmentation using the Freesurfer software. Volume of each brain region was normalized by the whole brain volume in order to minimize age and body size effects. Volume and cortical thickness variations among groups were compared. Atrophy was observed in the hippocampus, amygdala, entorhinal cortex, parahippocampal region, temporal pole and temporal lobe of patients suffering from AD at any stage. Cortical thickness was reduced only in the parahippocampal gyrus at all disease stages. Volume and cortical thickness were correlated with the Mini Mental State Examination (MMSE) score in all studied regions, as well as with CDR and disease duration. As previously reported, brain regions affected by AD during its initial stages, such as hippocampus, amygdala, entorhinal cortex, and parahippocampal region, were found to be altered even in individuals with severe AD. In addition, individuals, specifically, with CDR 3, have multiple regions with lower volumes than individuals with a CDR 2. These results indicate that rates of atrophy have not plateaued out at CDR 2-3, and in severe patients there are yet neuronal loss and gliosis. These findings can add important information to the more accepted model in the literature that focuses mainly on early stages. Our findings allow a better understanding on the AD pathophysiologic process and follow-up process of drug treatment even at advanced disease stages.
MeSH Terms
- Aged
- Aged, 80 and over
- Alzheimer Disease
- Atrophy
- Brain
- Brain Mapping
- Female
- Humans
- Male
- Neurodegenerative Diseases
- Organ Size
Keywords
- Aging
- Alzheimer's disease
- Brain atrophy
- Cortical thickness
Previous studies established that retrovirally infected young mice produced large amounts of autoantibodies to certain T-cell receptor (TCR) peptides whose administration diminished retrovirus-induced immune abnormalities. C57BL/6 young (4 weeks) and old (16 months) female mice were injected with these same synthetic human TCR V beta 8.1 or 5.2 peptides. Administration of these autoantigenic peptides to old mice prevent immunosenescence, such as age-related reduction in splenocyte proliferation and interleukin-2 (IL-2) secretion. TCR V beta peptide injection into young mice had no effect on T- or B-cell mitogenesis and IL-4 production while modifying tumour necrosis factor-alpha (TNF-alpha), IL-6, and interferon-gamma (IFN-gamma) secreted by mitogen-stimulated spleen cells. TCR V beta injection also retarded the excessive production of IL-4, IL-6 and TNF-alpha induced by ageing. These data suggest that immune dysfunction and abnormal cytokine production, induced by the ageing process, were largely prevented by injection of selected TCR V beta CDR1 peptides.
MeSH Terms
- Aging
- Animals
- Autoantibodies
- Body Weight
- Cell Division
- Cytokines
- Female
- Humans
- Immune Tolerance
- Mice
- Mice, Inbred C57BL
- Mitogens
- Peptide Fragments
- Receptors, Antigen, T-Cell, alpha-beta
- Spleen
We used synthetic peptides to analyze the human natural antibody response to V beta determinants. A major determinant recognized by IgM and IgG autoantibodies of clinically healthy individuals as well as those suffering from rheumatoid arthritis (RA) was a peptide corresponding to the first complementarity-determining region (CDR1). The natural IgM response of RA patients to this synthetic autoepitope was significantly elevated relative to that shown by healthy individuals. The levels of IgM reactivity to determinants corresponding to this region decreased with increasing age. By contrast, IgG autoantibodies to certain V beta CDR1 peptides increased markedly with age. In order to determine whether the CDR1 V beta determinant might be involved in immunization, we immunized rabbits with a human peptide that is greater than 80% identical to the homologous sequence derived from a rabbit V beta gene. As a control, the rabbits were immunized with a peptide of equal length derived from the N-terminus of the human V beta chain. Like humans, rabbits tended to have high levels of autoantibodies to the CDR1 peptide but not to the N-terminal segment. Following immunization, the rabbits produced strong IgG responses to the N-terminal peptide. By contrast, immunization with the CDR1 peptide resulted in levels of IgG antibody less than or equal to the natural activity in unimmunized rabbits. These studies indicate that the CDR1 region of Tcr V beta is a widely recognized autoantigenic portion of the Tcr that most probably functions as a regulatory epitope in man and other species.
MeSH Terms
- Adult
- Aged
- Aged, 80 and over
- Aging
- Amino Acid Sequence
- Arthritis, Rheumatoid
- Autoantibodies
- Autoimmune Diseases
- Dose-Response Relationship, Immunologic
- Enzyme-Linked Immunosorbent Assay
- Female
- Humans
- Immunoglobulin G
- Immunoglobulin M
- Immunoglobulin Variable Region
- Immunoglobulins, Intravenous
- Lupus Erythematosus, Systemic
- Male
- Middle Aged
- Molecular Sequence Data
- Ovalbumin
- Receptors, Antigen, T-Cell, alpha-beta
- Sequence Alignment
- Sequence Homology, Amino Acid
We used synthetic peptides duplicating the structures of a human lambda light chain (Mcg), and a human T-cell receptor (Tcr) alpha and a Tcr beta chain predicted from gene sequence to determine the presence and loci of activity of natural human autoantibodies directed against these antigen recognition molecules. We report that normal individuals and patients suffering from autoimmune diseases have antibodies directed against regions of lambda light chains and Tcr beta chains corresponding to the first complementarity determining region and the third framework region of the variable domain and to constant region determinants. The levels of IgM natural antibodies particularly against the CDR1 peptides tend to be higher in RA patients than in normals or SLE patients. Although polyclonal IgG immunoglobulins from healthy individuals did not show detectable reactivity to Tcr alpha peptides, such reactivity was found in the IgM immunoglobulins of RA patients, thereby showing that Tcr alpha peptides can be autoantigenic in man. The levels of IgM autoantibodies to V beta CDR1 peptides tend to decrease with age. By contrast, there was a marked increase in IgG natural autoantibodies to certain CDR1 sequences with advancing age. We suggest that the natural antibodies to defined regions of immunoglobulins and T-cell receptors are part of a physiological network for the regulation of the immune response.
MeSH Terms
- Adult
- Aged
- Aged, 80 and over
- Aging
- Amino Acid Sequence
- Animals
- Antibody Specificity
- Arthritis, Rheumatoid
- Autoantibodies
- Autoantigens
- Autoimmune Diseases
- Enzyme-Linked Immunosorbent Assay
- Humans
- Immunoglobulin G
- Immunoglobulin Light Chains
- Immunoglobulin M
- Molecular Sequence Data
- Myeloma Proteins
- Peptide Fragments
- Rabbits
- Receptors, Antigen, T-Cell, alpha-beta
- Reference Values
Immunoglobulins and their close relatives, the antigen-specific T-cell receptors, are recognition proteins that express structures which readily serve as self-immunogens. Healthy humans can produce antibodies against variable region-defined recognition structures termed idiotypes, as well as against constant region structures, and the levels of these can increase markedly in autoimmune disease; e.g., rheumatoid factors are autoantibodies directed against a conformational determinant of the gamma heavy chain. More recent analyses employing synthetic peptide technologies and construction of recombinant T-cell receptors document that autoantibodies directed against both variable and constant region markers of the alpha/beta T-cell receptor occur in healthy individuals. Alterations in levels of antibody, usage of IgM or IgG isotypes, and specificity for particular peptide-defined regions vary with natural physiological processes (aging, pregnancy), with artificial allografting, with retroviral infection, and with the inception and progression of autoimmune disease (e.g., rheumatoid arthritis, systemic lupus erythematosus). Two of the major autoimmunogeneic regions of the Tcr alpha/beta are "constitutive" markers inasmuch as all individuals tested produce antibodies against these regions. The most frequently observed autoantibodies are against Tcr V beta CDR1 and Fr3 markers. It is hypothesized that these are normally involved in immunoregulation. Autoantibodies usually are not detected against CDR2 region determinants, or the "private idiotypes" defined by the CDR3 region, or the highly conserved FR4 segment specified by the joining gene segment. However, autoantibodies against the CDR2 of the Tcr alpha chain occur in some SLE patients, and healthy pregnant women produce antibodies against the common peptide determinant expressed by the joining gene and the beginning of the C alpha or C beta domain. Although the precise role of the naturally occurring autoantibodies in immunoregulation remains to be determined, modification of the course of autoimmune diseases in experimental rodent models (experimental allergic encephalomyelitis) has been successfully carried out by immunization with synthetic peptides corresponding to the CDR2 and Fr3/CDR3 segments, and immunization of humans with synthetic V beta CDR2 segments may prove helpful in multiple sclerosis. Moreover, infusion of intravenous immunoglobulins has been successful in the treatment of many autoimmune diseases, including examples where levels of T cells bearing particular V beta gene subsets were elevated. The recent knowledge gained from T-cell receptor structural analysis and antigenic modeling holds promise for determining the roles of particular variable domain structures in antigen recognition MHC-restriction and immunoregulation, and in the development of synthetic and recombinant reagents for modulation of autoimmune and infectious diseases.
MeSH Terms
- Aging
- Amino Acid Sequence
- Animals
- Autoantibodies
- Autoantigens
- Autoimmunity
- Epitope Mapping
- Humans
- Immunoglobulins
- Models, Molecular
- Molecular Sequence Data
- Peptide Fragments
- Receptors, Antigen, T-Cell
- Retroviridae Infections
We describe monoclonal antibodies (MAB) reactive with subsets of mouse and human thymic epithelial cells. Rat MAb CDR1 reacts with mouse but not human cortical epithelial cells. Immunologic staining of thymic nurse cells in suspension indicates the CDR1 antigen is located on the cell surface. Mouse MAb CDR2 reacts with human but not mouse cortical thymic epithelial cells. Rat MAb MD1 and MD2 detect different determinants expressed by most medullary epithelial cells in mouse thymus but fewer such cells in human thymus. In addition, MD1 detects flattened subcapsular cells rarely in mouse thymus but frequently in human thymus. Two-color stains using an anti-keratin antiserum demonstrate the epithelial nature of the cells reactive with these antibodies. The antigens detected by CDR1 and MD1 first appear during the neonatal period, achieving adult distribution by postnatal days 14 and 4, respectively. The extra-thymic staining of these MAb is described. On the basis of their intra- and extra-thymic reactivities, these MAb differ from those previously reported and may permit dissection of the thymic microenvironment.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Antibodies, Monoclonal
- Antigens, Surface
- Epithelium
- Histocytochemistry
- Humans
- Immunoenzyme Techniques
- Keratins
- Male
- Mice
- Mice, Inbred AKR
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Rats
- Thymus Gland