In the present study, the effects of lipopolysaccharide (LPS) isolated from Salmonella Enteritidis were investigated by in vivo and in vitro methods. The mean lethal dose of 50% death (LD(50)) was determined by a Probit test as 450-mu g/mouse after 72 h post-treatment of LPS. Madin-Darby bovine kidney (MDBK), baby hamster kidney (BHK), mouse fibroblastic cell-lines (L929), and hybridoma cell lines were treated with different amounts of LPS (0-100 mu g/ml) cultivated for 72 h in 24 well tissue culture plates. Morphological investigation was done with inverted microscope after Giemsa staining. The results suggested that MDBK, BHK, and L929 cell lines were resistant to LPS cytotoxicity due to lack of the specific membrane receptor unlike hybridoma cells. After immunisation, one priming and seven booster's diluted sera (1:100) antibody level was found to be 2.00 +/- 0.06-2.41 +/- 0.07 optical density (OD) by enzyme linked immunosorbent assay (ELISA) on day 142. This result indicated that the LPS, instead of whole bacteria, have potential application in the immunisation.