Abstract:
The present study was undertaken to elucidate the immunomodulatory potential of five
medicinal plants which are used by traditional and Ayurveda practitioners of Sri Lanka to
treat various ailments. Ethanolic extracts of roots of Clerodendrum infortimatum Linn.,
Croton laccifer Linn, and Solanum surattense Burm.f., rhizomes of Alpinia calcarata
Rose, and tubers of Cyperus rotundus Linn, were tested on a rat model at doses of 50, 100
and 200 mg/Kg/day via oral route. Immunomodulatory activity was assessed in terms of
inflammatory response, differential leukocyte count, granulocyte adhesion, modulation of
cytokines including XL-1 (3, IL-4, IL-6, IL-10, IL-12, IFN-y and TNF-a and immunological
memory. As indicated by the results of CRBC induced inflammatory response assay (Paw
Edema Assay) rats treated with plant extracts showed significantly higher (P<0.05) paw
edema thickness and shorter recovery periods in comparison to control rats indicating a
possible strong cell mediated immune response induced by plant extracts. In the case of
secondary exposure to the same antigen after seven days from first challenge rats treated
with plant extracts showed rapid inflammatory response and recovery rates in comparison
with primary challenge indicating a significant buildup of short term immunological
memory induced by plant extracts. As suggested by granulocyte adhesion assay rats treated
with the plant extracts showed significantly higher adhesion percentages (PO.05) in dose
independent manner in comparison with the control rats indicating a probable up regulation
of expression in cellular adhesion molecules of granulocytes. The tested plant extracts
especially at higher doses induced cell mediated immunity by significantly increasing
(P<0.05) granulocyte, monocytes and hence total leukocyte count. Further treatment of
tested plant extracts did not significantly alter the hematological parameters such as RBC
count, HGB, HCT, Platelet Count, RDW, PDW and P-LCR indicating specific action of
these plant extracts on immune cells. In vivo cytokine assay suggested that tested plant
extracts stimulated the production of cytokines for varying degrees in a dose dependent
manner in comparison with control groups. In contrast to control group rats treated with
plant extracts showed enhanced survival ratios indicating a potential tolerance against
immunosuppression induced by cyclophosphamide. In this context these findings have
contributed to reasonably conclude that all the five plant extracts are positive
immunomoduLitors in innate immunity.
'Key words: Immune system, Medicinal plants, Immunomodulation, Cytokines,
Leukocytes, Inflammation, Immunological memory.
