Abstract
Phyllanthus amarus
(family: Euphorbiaceae) is of immense interest due to its wide spectrum of biological activities. In the present study, the standardized 80% ethanol extract of
P. amarus
was investigated for its modulatory activity on various cellular immune parameters, including chemotaxis of neutrophils, engulfment of
Escherichia coli
by neutrophils, and Mac-1 expression, in leukocytes isolated from treated/nontreated Wistar-Kyoto rats. The detailed cell-mediated activity of
P. amarus
was also investigated, including analysis of the effects on T- and B-cell proliferation and CD4
+
and CD8
+
T-cell subsets in splenic mononuclear cells, and estimation of serum cytokine production by activated T-cells. The main components of the extract, phyllanthin, hypophyllanthin, corilagin, geraniin, ellagic acid, and gallic acid were identified and quantitatively analyzed in the extracts, using validated reversed-phase high-performance liquid chromatography (HPLC) methods. N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced neutrophils isolated from rats administered with the extract of
P. amarus
, at doses ranging from 100 to 400 mg/kg for 14 days, revealed a significant dose-dependent reduction in neutrophil migration (
P
<0.05). Similar patterns of inhibition were also observed in phagocytic activity and in fMLP-induced changes in expression of β
2
integrin polymorphonuclear neutrophils. The results in
P. amarus
-treated rats also demonstrated a dose-dependent inhibition of both lipopolysaccharide-stimulated B-cell proliferation and concanavalin A–stimulated T-cell proliferation as compared with sensitized control. At a dose of 400 mg/kg (
P
<0.01), there was a significant decrease in the (%) expression of CD4
+
and CD8
+
in splenocytes and in serum cytokines of T helper (Th1) (IL-2 and IFN-γ) and Th2 (IL-4). In conclusion,
P. amarus
showed effective immunosuppressive activities in cellular immune response, by various immune regulatory mechanisms, and may be useful for improvement of immune-related disorders.