Aims: The activation of cellular and humoral immunity depends upon nature of antigens. Complex proteins like bacterial outer membrane proteins (OMP) usually successfully activate both humoral and cellular immunity. Whereas antigens like bacterial lipopolysaccharides (LPS) usually elicit T-independent immunity i.e. humoral immunity without the activation of cellular immune wing. The present study was under taken to evaluate the comparative immunologic behavior of both the important molecules (bacterial lipopolysaccharide and outer membrane proteins) of Pasteurella multocida alone and in combination in bovine calves in field conditions. Methodology and results: Pasteurella multocida was isolated, purified and identified from an outbreak by mean of culture and biochemical methods. The pathogenicity of the confirmed isolates was done in rabbits (Oryctolagus cuniculus) on the principles of Koch’s postulates. Alum based vaccine against P. multocida was prepared and antibody titer against Outer membrane protein (OMP) and lipopolysaccharides (LPS) were determined by complement fixation test (CFT). The results showed that the antibody titer against OMP and LPS in whole culture vaccine is significantly higher than the respective tested vaccines. These results concluded that OMP no doubt is an active T-dependent immunogenic molecule but its immunogenicity increases many times when combined with LPS in whole culture vaccine. Conclusion, significance and impact of study: Lipopolysaccharides (LPS) in combination with outer membrane proteins (OMP) synergistically boost the humoral immune response in vaccinated animal.