Exam 1 Review:  Chapter 17:  Leukocyte Defense Mechanisms

emigration - The movement of white blood cells by amoeboid movement (diapedesis) between the endothelial cells lining capillaries and small blood vessels in order to patrol the tissue spaces; the rate increases during the inflammatory process when chemotactic chemical signals encourage this activity.

phagocytosis - A form of endocytosis; the engulfing and ingesting of bacteria or other foreign bodies into membrane-bound vesicles (phagosomes) by phagocytes which surround the bacterium or foreign body with cytoplasmic extensions (pseudopods); after ingestion, the phagosome merges with lysosomes to form phagolysosomes where chemical digestion of the bacterium or foreign body occurs.

chemotaxis - The characteristic movement or orientation of an organism or cell along a chemical concentration gradient either toward (+) or away from (-) the diffusing chemical stimulus; it affects the direction of motion rather than the rate of motion; it is an important property of leukocytes in responding to injury and inflammation.

lysozyme - A hydrolytic enzyme occurring in mucous secretions and in the lysosomes of phagocytic cells, capable of destroying the cell walls (peptidoglycan) of bacteria, particularly gram-positive species.

strong oxidants - Chemicals, e.g., O radicals and H₂O₂, which are highly reactive electron acceptors capable of attacking biological molecules indiscriminantly; such compounds are generated as accidental byproducts in many biochemical reactions and may contribute to tissue damage; such compounds are generated by certain immune cells, particularly phagocytes, as one method of attacking and destroying foreign molecules and cells.

defensins - The group of small positively charged (cationic) proteins (peptides) stored in the small azurophilic granules of neutrophils which are biochemically active against the membranes of bacteria, fungi, and enveloped viruses, making them more permeable.

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