CD27 and tuberculosis: Prompted by the finding of phenotypically atypical (CD21-CD27- or IgD-CD27-) B-cells in the circulation of active TB patients, we isolated CD19+ B-cells from all groups and stimulated equal numbers of these cells with a strong polyclonal activation signal, consisting of anti-CD40 combined with anti-IgG/IgM antibodies to assess the functional properties of these B-cells.