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ABSTRACT
Previous studies have shown that the ethanol extract of Plumbago zeylanica. L. stems (EPZ) suppresses immediate allergic reactions. We extended these studies to examine the effect of EPZ on delayed-type hypersensitivity reactions. Our results showed that EPZ (500 and 1000 mg/kg), orally administered during either sensitization stage or effector stage, effectively attenuated picryl chloride–induced delayed-type hypersensitivity (PC-DTH) in mice. In vitro., EPZ (100 and 200 µg/ml) concentration-dependently inhibited Con A–induced splenocyte proliferation and interleukin-2 (IL-2) production but had little effect on nitric oxide (NO) production from murine peritoneal macrophages activated with lipopolysaccharide (LPS). EPZ (500 and 1000 mg/kg) also showed a significant inhibition of ear swelling caused by xylene in mice. These results suggested that EPE alleviated delayed-type hypersensitivity in mice, which might be attributable to inhibition of proliferation and differentiation of T lymphocytes as well as anti-inflammatory activities.