Immunophenotyping of B-Cell AND T-CELL ABNORMALITIES IN PID USING EUROFLOW-BASED PANELS

Abstract

Background: Predominantly antibody deficiency (PAD) is characterised by severe and recurrent bacterial infections, and up to 68% of patients develop non-infectious complications (NIC) including autoimmunity. Because the aetiology of NIC is unknown, we aimed to identify immune cell markers that associate with NIC in PAD patients. Methods: We developed an 11-colour flowcytometry panel and performed in-depth analysis of B- and T-cells in 53 adult PAD patients and 59 age-matched controls. Results: The patients were not genetically defined, and 30 (57%) had one or more NIC, 24 patients had reduced B-cell and 17 reduced T-cell numbers. Both PAD-NIC and PAD+NIC groups had significantly reduced Ig class-switched memory B cells, and naive CD4 and CD8 T-cell numbers. Naive and IgM memory B cells, Treg, Th17, and Tfh17 cells were specifically reduced in the PAD+NIC group. CD21lo B-cell and Tfh cells were increased in frequencies, but not in absolute numbers in PAD+NIC. Conclusion: The increased CD21lo B-cell and Tfh-cell frequencies are the indirect result of reduced naive B-cell and T-cell numbers. Hence, absolute cell counts are critical for correct interpretation of immunophenotyping of immunodeficiencies. The defects in naive B- and T-cell numbers suggest a mild combined immunodeficiency in PAD patients with NIC.