1Department of Immunology, Birjand University of Medical Sciences, Birjand, Iran
2Immunology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
3Department of Allergy and Immunology, Ghaem Hospital, Mashhad, Iran
Background: Invariant natural killer cells (iNKT) are an important immunoregulatory T cell subset. Currently several flow cytometry-based approaches exist for the identifi-cation of iNKT cells, which rely on using the 6B11 monoclonal antibody or a combina-tion of anti-Vα24 and anti-Vβ11 antibodies. Objective: The aim of this study was to compare the ability of two flow cytometry-based methods for detecting the frequency of circulating iNKT cells. Methods: The frequency of iNKT cells was detected in the pe-ripheral blood of 37 healthy adult donors by flow cytometry using the 6B11 antibody or a combination of anti-Vα24 and anti-Vβ11 antibodies. Results: The frequency of iNKT cells detected by 6B11 antibody or by combination of anti-Vα24 and anti-Vβ11 anti-bodies was significantly different (0.54% vs. 0.31%, respectively, p<0.001) but the val-ues were highly correlated (Spearman r = 0.742, p<0.0001). Conclusion: The results of this study indicate that different combinations of mAbs detect different frequencies of peripheral blood iNKT cells and a consensus in the field needs to be established to al-low better assessment of iNKT-related studies and suggest using different methods for accurate identification of iNKT cells.