Introduction: Leprosy is a chronic infectious granulomatous disease caused by M. leprae, which affects mainly the skin and peripheral nervous system. For treatment purposes leprosy is classified as paucibacillary (PB) and multibacillary (MB). Interleukin-4 is a typical Th2 cytokine and mediator of the Th1/Th2 balance.

Aims: Estimation of serum interleukin-4 (IL-4) levels in leprosy patients and compare & correlate with the values of controls.

Materials and methods: The present study was conducted in Department of Biochemistry and Dermatology & Venerology, SGT Medical College, Hospital & Research Institute, Budhera, Gurugram, Haryana and Civil Hospital Gurugram, Haryana. Serum IL-4 was estimated in 50 patients and 50 control by using enzyme linked immunosorbent assay (ELISA).

Result: Serum IL-4 was significantly higher in cases (35.20 ± 4.91 pg/mL) compared to controls (5.52 ± 1.27 pg/mL, p<0.000). Serum IL-4 level was also higher in multibacillary patients (37.40 ± 2.29 pg/mL) compared to paucibacillary patients (26.4 ± 0.90 pg/mL).

Conclusion: The increase in serum IL-4 levels indicates the association of disease progression with Th2 activation.