B-cells with a FasL expressing regulatory phenotype are induced following successful anti-tuberculosis treatment.

Studies show that B-cells, in addition to producing antibodies and antigen-presentation, are able to produce cytokines as well. These include regulatory cytokines such as IL-10 by regulatory B-cells. Furthermore, a rare regulatory subset of B-cells have the potential to express FasL, which is a death-inducing ligand. This subset of B-cells have a positive role during autoimmune disease, but has not yet been studied during tuberculosis. These FasL-expressing B-cells are induced by bacterial LPS and CpG, thus we hypothesized that this phenotype might be induced during tuberculosis as well. B-cells from participants with TB (at diagnosis and during treatment) and controls were collected, and analyzed by means of real-time PCR and flow cytometry. In addition to this, BAL was collected from TB participants as well and analyzed by means of MAGPix (multi-cytokine) technology. Gene expression analysis show that FASL transcript levels increase by the end of treatment. Similarly, phenotypic analysis show that there is a higher frequency of FasL-expressing B-cells by the end of treatment. Collectively, these results indicate that these FasL-expressing B-cells are being induced during anti-TB treatment, and thus may play a positive role. Further studies are required to elucidate this.