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Abstract

It has been suggested that neutrophil (PMN) specific granules are important in cell aggregation, locomotion, hydroxyl radical formation, and in extracellular functions such as the generation of complement- related inflammatory mediators (C5a) and the feedback regulation of myelopoiesis. In the current studies, a 9-yr-old boy with a history of recurrent infections and specific granule deficiency (absent lactoferrin, B-12 binding proteins, and characteristic specific granules on sucrose gradient centrifugation of cell homogenates) was studied to assess some of these concepts. In vivo, the patient had decreased PMN and monocyte accumulation into Rebuck skin windows but an expected febrile episode with an associated neutropenia (PMN margination) and neutrophilia (mobilization of marrow reserves) in response to intravenous endotoxin. In vitro, the patient's resting PMN showed increased ruffling, increased surface-to-volume ratio, and increased numbers of centriole-associated microtubules. His PMN showed a significant decrease in cell negative surface charge (which may relate to aggregation) in response to several stimuli and adhered better than normally to plastic. In addition, his PMN aggregated normally in response to the chemoattractant f-met-leu-phe, although the subsequent disaggregation normally seen with PMN did not occur with the patients cells. Chemotaxis of the patient's PMN to several stimuli was abnormal, and specific saturable and displaceable binding of the chemoattractant f-met-leu-[3H]phe was decreased. Similarly, following incubation with secretagogues, there was a less than normal increase in f-met-leu-[3H]phe binding and an absence of the normal increases in PMN surface area. The patient's PMN bactericidal activity, stimulated oxygen metabolism (cytochrome-c reduction, chemiluminescence, and NBT reduction), and elicited changes in membrane potential were also abnormal. Studies assessing the mechanism for the abnormal monocyte accumulation into skin windows indicated the patient's monocyte chemotaxis was better than normal in vitro. However, the patient's PMN homogenates lacked a stimulus of monocyte locomotion and did not generate chemotactic activity normally from serum. Thus, the data indicate that specific granule constituents are not required for neutrophil margination in vivo or aggregation in vitro. However, the data support the concept that PMN-specific granules are important for PMN locomotion and oxidative metabolism. In addition, extracellular release of specific granule constituents appears to be important for amplification of the initial and subsequent phases of the inflammatory response.