Cytokine polarized natural killer T cells modulate effector T cell function in leprosy

Area of Science:

• Immunology
• Infectious Diseases
• Cell Biology

Background:

• Leprosy exhibits a spectrum of clinical manifestations linked to host immune responses, primarily Th1 (Tuberculoid/borderline tuberculoid - TT/BT) and Th2 (Lepromatous/borderline lepromatous - LL/BL) polarization.
• The role of Natural Killer T (NKT) cells, which bridge innate and adaptive immunity, in leprosy immunopathogenesis remains incompletely understood.

Purpose of the Study:

• To investigate the frequency, cytokine profiles, and chemokine receptor expression of NKT cells in leprosy patients.
• To elucidate the functional contribution of NKT cells to the distinct immune responses observed in different leprosy clinical forms.

Main Methods:

• Flow cytometry was used to analyze NKT cell frequencies and phenotypes (CD3+CD161+).
• Intracellular cytokine staining assessed IFN-γ and IL-4 production by NKT cells.
• Sequential stimulation and cytokine-blocking experiments evaluated NKT cell-mediated modulation of T cell responses.
• Chemokine receptor expression (CCR4, CCR5, CXCR3, CCR6) on NKT cells was analyzed.

Main Results:

• BT/TT patients displayed increased frequencies of IFN-γ-producing NKT cells, correlating with Th1 immunity.
• BL/LL patients showed elevated IL-4-producing NKT and invariant NKT (iNKT) cells, associated with Th2 responses.
• NKT-derived IFN-γ enhanced Th1 responses in BT/TT, while IL-4 suppressed Th1 activity in BL/LL.
• Differential chemokine receptor expression (CCR6 in BT/TT; CCR4, CCR5, CXCR3 in BL/LL) indicated distinct migratory patterns.

Conclusions:

• Cytokine-polarized NKT cells play a critical role in modulating effector T cell function, contributing to the clinical heterogeneity of leprosy.
• NKT cells represent potential immunoregulatory targets for novel therapeutic strategies in leprosy and other chronic infections.