This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cellular Pathology, Subject name: Pathology
[{'content': 'All are involved in phagocytosis except: \nSelect and explain. \nA. Recognition and attachment, B. Engulfment, C. Pavementing of cells, D. Killing and degradation', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans: c (Pavementing of cells) Ref: Robbins, 7th ed, p. 59Phagocytosis involves 3 steps; they are:1. Recognition and attachment: Receptor involved are mannose receptors and scavenger receptors. The efficiency is greatly enhanced by opsonisation. Major opsonins are IgG, C,b breakdown products and lectins (MB,)2. Engulfment: Extension of cytoplasm as pseudopods around the particle to be engulfed, resulting in complete enclosure of the particle within the phagosome created by the plasma membrane of the cell.3. Killing and degradation:- by neutrophils and macrophages largely by oxygen dependent mechanisms, producing reactive oxygen metabolites (ROIs)- ROI is produced due to the activation of NADPH oxidase in the lysosome- The H2O2 - MPO- halide system is the most efficient bactericidal system', 'role': 'assistant'}]