Effect of Ajuga bracteosa on systemic T-cell immunity in Balb/C mice: dual Th1/Th2 immunostimulatory effects

Ajuga bracteosa (AB) has been widely used in folk medicine in Asian countries against gout, hepatitis, pneumonia, rheumatism, and various neuro inflammatory disorders. The aim of this study was to investigate the possible immunoregulatory effects of the ethanolic extract of Ajuga bracteosa (ABEE) on systemic Th1/Th2 immunity in SRBC immunized Balb/C mice. Animals were orally administered with graded doses of ABEE from 6.25 mg/kg to 100 mg/kg. Post sub-cutaneous immunization with SRBCs and circulating antibody titers, DTH responses and splenocyte proliferation was monitored as markers of Th2 and Th1 responses. Cyclophosphamide and levamisole were used as controls. Lymphocyte immunophenotying (CD4/CD8 cell counts) and intracellular Th1/Th2 cytokine concentrations were determined using flow cytometry. Treatment with ABEE demonstrated significant biphasic immunostimulation of effector T-helper immunity. ABEE at 50 mg/kg dose resulted in maximal increase in antibody titers, DTH responses and CD4+/CD8+ T-cell percentages indicating maximal activation and proliferation of T and B lymphocytes at this dose. ABEE, at the same dose, also showed maximal up regulation of LPS and CON A stimulated splenocyte proliferation and also maximal up-regulation of both Th1 (IL-2, IFN-γ) and Th2 (IL-4) cytokines which suggest its mixed Th1/Th2 immunostimulatory activity. Comparatively at higher doses (100 mg/kg), significant down regulation of all these effector T-helper (Th) immune responses was observed. The study therefore suggests mixed biphasic immunostimulatory Th1/Th2 activity of ABEE that could support its immunoadjuvant potential.