Enterobacterial infection modulates major histocompatibility complex class I expression on mononuclear cells.

Area of Science:

• Immunology
• Microbiology
• Genetics

Background:

• Major histocompatibility complex (MHC) class I expression is known to decrease during viral infections.
• The effect of intracellular enterobacterial infections on MHC class I expression in vivo remains largely uncharacterized.

Purpose of the Study:

• To investigate the expression of MHC class I antigens on peripheral blood mononuclear cells (PBMC) during infections caused by intracellular enterobacteria.
• To determine if HLA-B27 genotype influences MHC class I expression during such infections.

Main Methods:

• Analysis of MHC class I antigen expression on PBMC from 16 patients with Salmonella, Yersinia, or Klebsiella infection.
• Genotyping for HLA-B27 and HLA-A2.
• Assessment of intracellular MHC class I antigen retention and HLA-B27 mRNA levels.

Main Results:

• Marked decrease in MHC class I antigen expression observed in eight patients, all carrying the HLA-B27 genotype, and six out of eight with reactive arthritis (ReA).
• Significant decrease in HLA-B27 expression noted in eight patients (P<0.05).
• Intracellular retention of MHC class I antigens occurred during surface expression decrease, without significant changes in HLA-B27 mRNA levels.

Conclusions:

• Enterobacterial infections can down-regulate MHC class I expression in vivo.
• This down-regulation is predominantly observed in patients with the HLA-B27 genotype.
• The findings suggest a specific interaction between enterobacteria, MHC class I regulation, and the HLA-B27 genotype.