Long-term follow-up on affinity maturation and memory B-cell generation in patients with common variable immunodeficiency.

Purpose: Common variable immunodeficiency (CVID) comprises a heterogeneous group of primary immunodeficiency disorders. Immunophenotyping of memory B cells at the time of diagnosis is increasingly used for the classification of patients into subgroups with different clinical prognoses. The EUROclass classification is a widely used method. Levels of somatic hypermutation (SHM) have proven useful as a prognostic marker for recurrent respiratory tract infections. As time of presentation and diagnosis is highly variable in CVID patients, and diagnostic delay is a common problem, it is important to know whether classification parameters are stable over time. The purpose of the study was to address this question in a cohort of 33 CVID patients followed from 3 to 19 years after diagnosis (average follow-up 8.8 years).

Methods: Levels of class-switched memory B cells were analyzed using flow cytometric immunophenotyping, and patients were classified according to the EUROclass criteria. Affinity maturation of B cells was measured using Igκ-REHMA, which assesses somatic hypermutation in kappa light chain transcripts. Clinical manifestations in terms of splenomegaly, autoimmune disease and granulomatous disease were also determined.

Results: Switched memory B cells and levels of SHM were not consistently stable markers in a long-term follow-up setting. At a given time during follow-up, 60% of the patients were assigned to the EUROclass group SmB- (less than 2% switched memory B cells), but only 23% were consistently assigned to this group. Associations between clinical manifestations and levels of switched memory B cells or SHM were not observed in our study.

Conclusion: Based on our findings, we suggest that immunologic characteristics in CVID patients should be evaluated several times after diagnosis using internationally standardized methods.