The selective augmentation by recombinant human tumour necrosis factor-alpha of neutrophil responses to pathogenic Escherichia coli.

Endotoxin release may amplify the neutrophil (PMN) responses to bacterial infection through the release of monocyte-derived tumour necrosis factor (TNF). The present study was designed to assess the effect of recombinant human TNF-alpha (rhTNF-alpha) on the in vitro response of human PMN to two defined strains of pathogenic Escherichia coli. In the absence of rhTNF-alpha, a P-fimbriate strain caused significant release of the PMN secondary granule marker vitamin B12-binding protein (B12 BP), and a low level of release of leukotriene B4 (LTB4). Type 1-fimbriate strain 504, however, stimulated the release of the primary granule marker myeloperoxidase (MPO) and PMN chemiluminescence (CL), in addition to B12 BP and LTB4 release. Following rhTNF-alpha (10(-9) M) pretreatment, the release of LTB4 by PMN stimulated with the P-fimbriate strain was synergistically augmented, while B12 BP and MPO release were additively increased. In contrast, rhTNF-alpha did not significantly affect any of the responses by the type 1-fimbriate strain. These results suggest selectivity in the priming of PMN by rhTNF-alpha and confirm the independence of PMN responses to phagocytic stimuli.