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Of leukocytes effects include enhanced adherence

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of leukocytes. Effects include enhanced adherence, enhancedchemotactic activity, release of proteinases, and production of toxicmetabolites of oxygen. C3, on the other hand, plays a key role inbacterial opsonization, resulting in enhanced phagocytosis of invadingmicroorganisms. The alternative and classical complement pathwaysconverge at the C5 level proximal to generating the membrane attackcomplex (C5b-9) (Figure 6-3).180 Which of the following statements regarding neutrophils are true?a. The neutrophil undergoes final maturation after release into thecirculationb. Patients with chronic granulomatous disease have a defectiveneutrophil H-oxidase systemc. Neutrophil killing of bacteria is achieved by oxidants, proteinasesand cationic proteinsd. The normal human neutrophil circulates in the blood for 7–10 daysAnswer: b, cThe neutrophil is a migratory phagocytic cell that defends the hostagainst bacteria and eliminates necrotic tissue. The neutrophilmatures in the bone marrow and is released into the circulation as afully differentiated cell. It is loaded with granules containing a varietyof proteinases, hydrolases, antimicrobial agents and cationic proteins.The cell phagocytoses material and the granules fuse with thephagocytic vacuoles to degrade the foreign material. When the cellsare challenged with a large amount of material, the granule contentsmay be released into the extracellular space where damage tosurrounding tissue occurs. The neutrophil normally circulates in thehuman bloodstream for 7 to 10 hours. Thereafter, neutrophils arethought to exist for 1 to 2 days in the tissues before being clearedfrom the system. Granule constituents are formed duringdifferentiation and replenishment of spent granules does not occuronce the cells are in the circulation. Hence, the neutrophil is a fullydifferentiated end-cell poised to respond rapidly to stimuli, but it israpidly spent in the process. Neutrophils have a NADPH-oxidaseenzyme system on the plasma membrane which can be activated toproduce toxic oxygen species including the superoxide anion (02–).Patients with chronic granulomatous disease (CGD) have a defective
NADPH-oxidase system in their neutrophils, and are thus unable togenerate 02–. Although neutrophils from patients with CGD are ableto phagocytose bacteria, they are unable to kill the intracellularmicrobes and chronic, unresolved infections result.181 Which of the following statements regarding the alternativecomplement pathway are true?a. C1, C4 and C2 are involvedb. NH3 apparently activates complement via this pathwayc. Factors B and D are involvedd. Endotoxin activates complement via the alternative pathwayAnswer: b, c, dThe alternative pathway differs from the classic pathway in that thefirst steps involving C1, C4 and C2 are bypassed. (See Figure 6-3previously reproduced.) This pathway can be directly activated byagents other than antigen–antibody complex (e.g., complexpolysaccharides like endotoxin and zymosan). Other serum proteinfactors (e.g., factors B and D) are involved in the activation sequence.

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