Expression and function of HLA-DR3 and DQ8 in transgenic mice lacking functional H2-M

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Human Leukocyte Antigen (HLA)-DM (also known as H2-M) are non-classical MHC class II molecules vital for antigen presentation.
• They facilitate the exchange of peptides within the peptide-binding groove of MHC class II molecules.
• H2-M deficiency can impact T-cell development and antigen responses, but its in vivo role with specific HLA class II molecules like DQ8 and DR3 is not fully understood.

Purpose of the Study:

• To investigate the in vivo function of H2-M in antigen presentation by HLA-DQ8 and HLA-DR3 molecules.
• To determine the effect of H2-M deficiency on CD4+ T-cell development and responses to various antigens and superantigens.

Main Methods:

• Utilized a transgenic approach in mice lacking H2-M.
• Expressed human HLA-DQ8 and HLA-DR3 molecules in H2-M-deficient and sufficient backgrounds.
• Assessed surface expression of MHC class II molecules, CD4+ T-cell development, peptide antigen presentation, superantigen presentation, and systemic IFN-gamma production following Staphylococcal Enterotoxin B (SEB) challenge.

Main Results:

• DQ8 and DR3 molecules were expressed at normal levels in H2-M-deficient mice, with unaltered CD4+ T-cell development.
• The ability of DQ8 molecules to present peptide antigens was compromised in H2-M-deficient mice.
• Presentation of bacterial superantigens by DQ8 and DR3 was unaffected by H2-M deficiency.
• H2-M-deficient DQ8/DR3 transgenic mice exhibited significantly higher SEB-induced IFN-gamma production and increased susceptibility to SEB-induced toxic shock.

Conclusions:

• H2-M is essential for efficient peptide antigen presentation by HLA-DQ8 in vivo, but not for superantigen presentation by DQ8 or DR3.
• H2-M deficiency leads to heightened inflammatory responses and susceptibility to toxic shock mediated by certain superantigens like SEB.
• These findings highlight a critical role for H2-M in modulating immune responses to specific antigens and superantigens.