This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Lipopolysaccharide of gram negative bacteria - 
Select and explain. 
A. Hapten, B. Heterophile antibody, C. Stimulator for B lymphocytes, D. Induce cell mediated immunity'
C: Stimulator for B lymphocytes
Answer: C: Stimulator for B lymphocytes 
Explanation: Ans. is 'c' i.e., Stimulator for B lymphocytes o The biological activity of endotoxin is associated with lipopolysaccharide (LPS).Toxicity is associated with lipid component (Lipid A).Immunogenicity is associated with polysaccharide component.o The cell wall antigen (O antigen) of Gram-negative bacteria are components of LPS.o LPS elicits a variety of inflammatory responses and activates alternate complement pathway,o The susceptibility to infections induced by Gram-negative bacteria is largely determined by innate immune response to bacterial cell wall lipopolysaccharide (LPS).o The stimulation of B-cells by LPS enhances their antigen-presenting capacity and is accompanied by B-cell proliferation and secretion of large qunatities of LPS neurilizing antibodies.