Functionally exhausted and mostly autoreactive B-cells with a peculiar CD21^lowCD11c⁺ phenotype accumulate in several human immunological disorders including common variable immunodeficiency, HIV infection and rheumatoid arthritis. In HCV-associated mixed cryoglobulinemia (MC) there is accumulation of exhausted clonal B cells expressing a V_H1-69-encoded cross-reactive idiotype; these cells are phenotypically heterogeneous, displaying either a CD21^lowCD11c⁺ or a marginal zone (MZ)-like (IgM⁺CD27⁺CD21⁺CD11c^-) phenotype. Irrespective of their phenotype, V_H1-69⁺ B-cells are unresponsive to the stimulation of Toll-like receptor 9 (TLR9). We investigated the fate of these cells after the eradication of HCV.

Fourteen MC patients were studied before and after antiviral therapy. V_H1-69⁺ B-cells were identified using the G6 monoclonal antibody and their phenotype and responsiveness to the stimulation of TLR9 were investigated.

In seven virological non-responders, cryoglobulin levels and the number and phenotype of V_H1-69⁺ B cells remained substantially unchanged. By contrast, in sustained viral responders cryoglobulinemia subsided and the number of V_H1-69⁺ B cells declined. However, high proportions of MZ-like V_H1-69⁺ B cells retaining unresponsiveness to TLR9 stimulation persisted for several months in these patients.

Clonal expansion of CD21^low V_H1-69⁺ B cells may depend on continual stimulation by HCV, whereas their MZ-like counterparts may persist for years after the eradication of infection. Prolonged survival of exhausted MZ-like B cells after withdrawal of the initial inciting stimulus may contribute to the accumulation of autoreactive B cells in immunological disorders.