Immunophenotyping of putative human B 1 B cells in healthy controls and common variable immunodeficiency ( CVID ) patients

Summary B 1 B cells represent a unique subset of B lymphocytes distinct from conventional B 2 B cells, and are important in the production of natural antibodies. A potential human homologue of murine B 1 cells was defined recently as a CD 20 + CD 27 + CD 43 + cell. Common variable immunodeficiency ( CVID) is a group of heterogeneous conditions linked by symptomatic primary antibody failure. In this preliminary report, we examined the potential clinical utility of introducing CD 20 + CD 27 + CD 43 + B1 cell immunophenotyping as a routine assay in a diagnostic clinical laboratory. Using a whole blood assay, putative B 1 B cells in healthy controls and in CVID patients were measured. Peripheral blood from 33 healthy donors and 16 CVID patients were stained with relevant monoclonal antibodies and underwent flow cytometric evaluation. We established a rapid, whole blood flow cytometric assay to investigate putative human B 1 B cells. Examination of CD 20 + CD 27 + CD 43 + cells is complicated by CD 3 + CD 27 + CD 43 hi T cell contamination, even when using stringent CD 20 gating. These can be excluded by gating on CD 27 + CD 43 lo–int B cells. Although proportions of CD 20 + CD 27 – CD 43 lo–int cells within B cells in CVID patients were decreased by 50% compared to controls ( P  < 0·01), this was not significant when measured as a percentage of all CD 27 + B cells ( P  = 0·78). Immunophenotypic overlap of this subset with other innate‐like B cells described recently in humans is limited. We have shown that putative B 1 B cell immunophenotyping can be performed rapidly and reliably using whole blood. CD 20 + CD 27 + CD 43 lo–int cells may represent a distinct B1 cell subset within CD 27 + B cells. CVID patients were not significantly different from healthy controls when existing CD 27 + B cell deficiencies were taken into account.