Figure 2.

Immunostimulatory activity of Dolichos lablab lectin (DLL) on human and murine lymphocytes in vitro. To investigate the mitogenic attribute of DLL, in‐vitro cultured lymphocytes were treated with varying lectin concentrations and subjected to 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazoliumbromide (MTT) proliferation assay, as told in the Methodology section. (a) Representative visual depictions of the purified DLL‐induced mitogenicity on human peripheral blood lymphocytes (2·5 × 10⁶ cells/ml) at 10 μg/ml concentration. The cell cluster formation, a prerequisite event in the cellular proliferation, could be observed in DLL, whereas untreated cells appear distinctively separated. Similar cell clusters were also observed in (b) murine splenocytes (c) and thymocytes. The true‐coloured and unstained images were observed through brightfield inverted microscope (Olympus) at ×20 optical magnification. The proliferative effect of DLL was expressed in terms of proliferative index. The index for control (non‐stimulated) cells was taken as 1·0 and for others it is calculated as a ratio of absorbance at 570 nm of the test sample to that of the control. Graphs indicating the proliferative index of DLL on human peripheral blood lymphocytes (PBLs) (d), splenocytes (e) and thymocytes (f) in vitro. (g) Effect of DLL on ex‐vivo interleukin (IL)‐2 production by human PBL and murine splenocytes. Results are the means of three determinations, each conducted in triplicate. Statistically significant values are *P < 0·05; ^** P < 0·01. [Colour figure can be viewed at wileyonlinelibrary.com].