Expression of essential B cell development genes in horses with common variable immunodeficiency

Area of Science:

• Immunology
• Veterinary Medicine
• Molecular Biology

Background:

• Common variable immunodeficiency (CVID) is a diverse B cell disorder marked by insufficient antibody production.
• Equine CVID model exhibits late-onset B cell lymphopenia from impaired bone marrow B cell production.

Purpose of the Study:

• To investigate B cell differentiation status in equine CVID bone marrow.
• To measure the expression of genes critical for early B cell commitment and development in affected horses.

Main Methods:

• Reverse transcription-polymerase chain reaction (RT-PCR) to assess gene expression.
• Quantitative RT-PCR to measure mRNA levels of E2A, PAX5, CD19, and IGHD.
• Immunohistochemical analysis for PAX5-BSAP expression.

Main Results:

• While early B cell transcription factors were present, PAX5 and related gene expression were variable in equine CVID.
• Significantly reduced mRNA expression of E2A, PAX5, CD19, and IGHD observed in CVID patients.
• Reduced PAX5/EBF1 and PAX5/B220 ratios and absence of PAX5-BSAP expression confirmed in affected horses.

Conclusions:

• B cell development appears impaired at the pre-pro-B to pro-B cell transition in equine CVID.
• This study identifies a specific molecular defect in B cell differentiation in this animal model of CVID.