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Published on: February 28, 2019
Determinant capture by MHC class II DR3 during processing of mycobacteria leprae 65kD heat shock protein by human B
S P Young1, E Epstein, V Potter
1Department of Rheumatology, University of Birmingham, UK. S.P.Young@bham.ac.uk
Insights
Researchers identified a specific 12kD peptide fragment from Mycobacterium Leprae heat shock protein associated with MHC class II DR3 in B cells. This finding highlights the role of MHC in capturing antigenic determinants during processing.
Area of Science:
- Immunology
- Molecular Biology
- Protein Chemistry
Background:
- Mycobacterium leprae heat shock proteins are crucial in leprosy pathogenesis.
- MHC class II molecules present antigens to T helper cells, initiating immune responses.
- Understanding antigen processing by B cells is vital for vaccine development.
Purpose of the Study:
- To characterize immunogenic fragments of Mycobacterium leprae 65kD heat shock protein.
- To investigate the association of these fragments with MHC class II DR3 during B cell processing.
- To elucidate the role of MHC in antigen degradation and determinant capture.
Main Methods:
- T cell immunoblotting was employed to analyze protein fragments.
- Human B cell lines were incubated with Mycobacterium leprae antigen.
- Competition assays with synthetic peptides and temperature-dependent studies were performed.
Main Results:
- A major 12kD peptide fragment (approx. 110 amino acids) of the 65kD heat shock protein was found associated with MHC class II DR3.
- This association was abolished by excess synthetic minimal epitope peptide, indicating specificity.
- The generation of the 12kD fragment and its binding to MHC class II were dependent on cellular metabolism.
Conclusions:
- A specific 12kD fragment of Mycobacterium leprae 65kD heat shock protein is generated during B cell processing.
- This fragment binds specifically to MHC class II DR3, suggesting it's a key intermediate.
- The study demonstrates the role of MHC in determinant capture during antigen processing.
Abstract:
Using T cell immunoblotting we have characterised the immunogenic fragments derived from the Mycobacteria Leprae 65kD heat shock protein that become associated with MHC class II DR3 during processing by a human B cell line. After 5 h incubation with antigen, a peptide of approximately 12kD (approximately 110 amino acids) was the only major fragment found associated with the class II MHC. The association of this oligopeptide was abolished if an excess of a synthetic peptide representing the minimal epitope was included in the culture or when cells were incubated at 4 degrees C. This suggests that the generation of this moiety is dependent on cell metabolism and that its binding to MHC is specific. This large fragment may represent an intermediate in the processing pathway, directly demonstrating the role of MHC in determinant capture during antigen degradation.
