Early activated Th-1 type and dominantly diverse natural killer T (CD3+CD161+Vα24−) cells in bone marrow among visceral leishmaniasis patients

► CD3+CD161+ natural killer T (NKT) cells are not enriched at the site of pathology among visceral leishmaniasis (VL) patients. ► Non-CD1d restricted, non-invariant NKT cells are the dominant population in the bone marrow (BM) of VL patients. ► Findings are indicative of an early activated phenotype of recruited NKT cells at disease site (BM). ► These cells were heterogeneous and pre-dominantly IFN-γ producing at the BM in response to Leishmania donovani antigen. ► Activation and polarisation of resident NKT cells may be due to a compensatory host mechanism to contain the pathology.