T cell suppression in the bone marrow of visceral leishmaniasis patients: Impact of parasite load

Summary

Visceral leishmaniasis (VL) is a disseminated and lethal disease of reticulo-endothelial system caused by protozoan parasites Leishmania donovani and Leishmania infantum, which are known to induce host T cell suppression. To understand the impact of parasite load on T cell function, the present study was focussed on parasite load with T cell function in bone marrow of twenty-six (26) VL patients. We observed significant enrichment of Foxp3⁺ (p = 0.0003) and IL-10⁺ Foxp3⁺ T-regulatory (Treg) cells (p = 0.004) in the BM of patients with high parasite load (HPL) as compared with low parasite load (LPL). Concordantly, T effector cells producing IFN-γ (p = 0.005) and IL-17A (p = 0.002) were reduced in the BM of HPL. Blocking of Treg cell derived suppressive cytokines (IL-10 and TGF-β) rescued the effector T cells and their functions. However, it was observed that TGF-β levels were dominant favouring Treg cell differentiation. Furthermore, the low ratio of IL-6/TGF-β favours the suppressive milieu in HPL patients. Here we show the change in levels of various cytokines with the parasitic load during active VL, which could be helpful in devising newer immunotherapeutic strategies against this disease. This article is protected by copyright. All rights reserved.