Cells involved in cellular response

Cells involved in cellular response:
i) Phagocytes:
• circulating monocyte leave blood stream  develop into macrophages (main phagocyte)
• neutrophils also become phagocytic when meet up with infectious material
• eosinophils are weakly phagocytic (more important against parasitic worms)
• phagocytes engulf material by cytoplasmic extensions surrounding it and pulling it inside, enclosing it in a membrane (phagosome)  fuses with a lysosome (phagolysosome)
• phagocytes kill micro-organism by lysosomal digestion; respiratory burst (liberation of free radical such as nitric oxide); defensins (antibiotic like chemicals);
• some microorganisms are difficult for phagocytes to adhere to capsular polysaccharides for ingestion – this can occur more easily after opsonisation (coating of the foreign particle by complement proteins and/or antibodies)

ii) Natural killer (NK) cells:
• circulate in blood and lymph
• react against virus infected cells and tumour cells
• destroy target cell’s membrane and releases cytolytic chemicals

Antimicrobial chemicals involved in cellular response:
i) Complement:
• group of 20+ plasma proteins that are normally in an inactive state in circulation
• when activated and fixed on a foreign cell’s membrane  lysis of cell and enhancement of phagocytosis

ii) Interferon:
• synthesised by virus infected cells and certain immune cells