<prompt> Which of the following activates the classical complement pathway?Immune complexLipopolysaccharideExotoxinZymosan  <response>: Ans: A Immune complex Ref: Ananthnarayan R, Partiker CKJ. Textbook of Microbiology. 8th Edition. Hyderabad: Universities Press: 2009.Explanation:Complement-pathwaysClassic pathway - Acquired immunity Activated by antigen antibody complexAlternate complement pathway - Innate immunity Activated by various substances like bacterial endotoxins, fungal cell wall components like zymosanMannanMannose Binding Lectin pathway MBL Pathway - Innate immunity Activated by the binding of mannose-binding lectin MBL to mannose residues on glycoproteins or carbohydrates on the surface of microorganisms including certain Salmonella, Listeria, and Neisseria strains, as well as Cryptococcus neoformans and Candida albicans.Sources of ComplementClassical pathwayC1-epithelium fibroblastsC3, C4. C6 -C9 -LiverCl -C5 -Macrophages stimulated by phagocytic eventsCI esterase -LiverAlternate pathwayFactor B. D. H. I. P -Macrophages stimulated by phagocytic events 