Low circulating B cells in immunocompromised individuals are linked to poorer antibody responses to vaccines and a predisposition to viral infections.

Background: B cells play an important role in protection against viral infections, not only through the production of antibodies but also through their ability to act as antigen-presenting cells and produce cytokines. Objectives: To assess whether there is a link between low circulating B-cell counts and a predisposition to viral infections in immunocompromised individuals, we performed a retrospective cohort analysis at 2 National Health Service Clinical Immunology sites in England. Methods: Eligible patients were adults who were either diagnosed with or under investigation for an immunodeficiency and had recorded circulating B-cell counts. Information on viral infections was collected by using the departmental, hospital, and laboratory electronic information systems. A generalized linear model was used to analyze the relationship between B-cell counts and relevant indices of viral infection while controlling for patient age, diagnosis group, and T-cell and natural killer cell counts. Results: A total of 376 eligible patients were identified, 134 of whom had B-cell counts that were below the laboratory-defined refence range (<0.11 ×10 Conclusion: Overall, there was a statistically significant association between low circulating B-cell counts and the incidence of clinically important viral infections in this patient cohort, even when controlling for relevant covariates. Clinicians caring for patients with immunodeficiency should be vigilant for these types of infections, particularly in patients with low peripheral B-cell counts. A prospective study will be required to confirm these findings.