Histocompatibility Complex Status and Mendelian Randomization Analysis in Unsolved Antibody Deficiency.

Area of Science:

• Immunology
• Genetics
• Human Pathology

Background:

• Common variable immunodeficiency (CVID) is the most frequent symptomatic primary immunodeficiency, yet its pathogenesis remains largely unknown in most patients.
• Identifying genetic factors contributing to CVID is crucial for understanding disease mechanisms and developing targeted therapies.

Purpose of the Study:

• To compare major and minor histocompatibility complex (MHC) markers and polygenic scores in CVID patients with and without identified genetic mutations.
• To investigate the causal role of genetic variants in CVID susceptibility and clinical phenotypes using Mendelian randomization (MR).

Main Methods:

• Whole exome sequencing to identify monogenic defects in CVID patients.
• Computational and PCR-based high-resolution MHC typing.
• Development of exome-wide polygenic scores and multi-variant MR analyses.

Main Results:

• Monogenic defects were identified in 40 out of 83 CVID patients.
• Significant associations were found between specific MHC class I and II alleles and CVID in non-monogenic cases.
• A distinct haplotype (W*01:01:01-DMA*01:01:01-DMB*01:03:01:02-TAP1*01:01:01) was strongly linked to a specific CVID phenotype.
• MR analyses identified genetic variants associated with bacterial infections and improved previous GWAS findings.

Conclusions:

• Exclusion of monogenic forms of CVID highlights an independent contribution of MHC genes and common genetic variants to CVID pathogenesis.
• This study provides novel insights into the genetic architecture of CVID, particularly in cases without known monogenic defects.
• The findings pave the way for a more comprehensive understanding of CVID etiology and potential genetic risk factors.