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Polyspecificity of antistreptococcal murine monoclonal antibodies and their implications in autoimmunity
Abstract:
mAbs produced by immunization of BALB/c mice with Streptococcus pyogenes M type 5 membranes were further characterized for their reaction with S. pyogenes pep M5 protein and with autoantigens associated with human cell lines. mAbs 36.2.2 and 54.2.8 simultaneously reacted with M protein and a membrane protein(s) of S. pyogenes. When cell lines were mixed with 54.2.8, we saw nuclear fluorescence along with staining of the cytoskeleton. Subsequent experiments revealed that 54.2.8 was an anti-DNA antibody that reacted with DNA, poly(I), poly(dT), and weakly with cardiolipin. Its reactivity with the cytoskeleton could be blocked with anti-vimentin. On the other hand, 36.2.2 reacted with the cytoskeleton, sparing the nucleus, and was inhibited by the alpha helical proteins myosin, actin, and keratin. mAb 54.2.8 was inhibited with myosin, but not with actin and keratin. None of the antibodies studied were inhibited by collagen, and none of them were rheumatoid factors. The results imply that Group A streptococci can activate B cell clones against myosin, alpha helical proteins, or DNA, thereby contributing to the enhancement of autoantibody production.
Insights
Streptococcus pyogenes M protein can trigger autoimmune responses. Antibodies against M protein also react with human DNA and cytoskeletal proteins, potentially leading to autoantibody production.
Area of Science:
- Immunology
- Microbiology
- Autoimmunity
Background:
- Streptococcus pyogenes is a pathogen associated with various infections.
- M protein is a key virulence factor of S. pyogenes.
- Autoantibodies can contribute to autoimmune diseases.
Purpose of the Study:
- To characterize monoclonal antibodies (mAbs) produced against Streptococcus pyogenes M type 5 membranes.
- To investigate the cross-reactivity of these mAbs with S. pyogenes components and human autoantigens.
- To explore the potential role of S. pyogenes in triggering autoimmune responses.
Main Methods:
- Immunization of BALB/c mice with S. pyogenes M type 5 membranes to generate mAbs.
- Characterization of mAb reactivity against M protein, bacterial membrane proteins, and human cell lines.
- Inhibition assays using various antigens (DNA, proteins) to determine antibody specificity.
Main Results:
- Two mAbs, 36.2.2 and 54.2.8, reacted with both M protein and S. pyogenes membrane proteins.
- mAb 54.2.8 showed nuclear and cytoskeletal fluorescence, identified as an anti-DNA antibody with cross-reactivity to vimentin.
- mAb 36.2.2 reacted with the cytoskeleton, inhibited by myosin, actin, and keratin, but not DNA or cardiolipin.
Conclusions:
- Group A streptococci, through M protein, may activate B cell clones targeting self-antigens like DNA and cytoskeletal proteins.
- This cross-reactivity could contribute to the development of autoantibodies and autoimmune conditions.
- The study suggests a potential mechanism linking streptococcal infections to autoimmunity.