<Li> Natural killer cells: virus - infected and tumor cells . </Li> <Tr> <Td> Monocyte </Td> <Td> </Td> <Td> </Td> <Td> 5.3% </Td> <Td> 15--30 </Td> <Td> Monocytes migrate from the bloodstream to other tissues and differentiate into tissue resident macrophages, Kupffer cells in the liver . </Td> <Td> Kidney shaped </Td> <Td> None </Td> <Td> Hours to days </Td> </Tr> <P> Neutrophils are the most abundant white blood cell, constituting 60 - 70% of the circulating leukocytes, and including two functionally unequal subpopulations: neutrophil - killers and neutrophil - cagers . They defend against bacterial or fungal infection . They are usually first responders to microbial infection; their activity and death in large numbers form pus . They are commonly referred to as polymorphonuclear (PMN) leukocytes, although, in the technical sense, PMN refers to all granulocytes . They have a multi-lobed nucleus, which consists of three to five lobes connected by slender strands . This gives the neutrophils the appearance of having multiple nuclei, hence the name polymorphonuclear leukocyte . The cytoplasm may look transparent because of fine granules that are pale lilac when stained . Neutrophils are active in phagocytosing bacteria and are present in large amount in the pus of wounds . These cells are not able to renew their lysosomes (used in digesting microbes) and die after having phagocytosed a few pathogens . Neutrophils are the most common cell type seen in the early stages of acute inflammation . The life span of a circulating human neutrophil is about 5.4 days . </P> <P> Eosinophils compose about 2 - 4% of the WBC total . This count fluctuates throughout the day, seasonally, and during menstruation . It rises in response to allergies, parasitic infections, collagen diseases, and disease of the spleen and central nervous system . They are rare in the blood, but numerous in the mucous membranes of the respiratory, digestive, and lower urinary tracts . </P>

Function of different types of white blood cells