Bovine melanoma growth stimulatory activity: a new monocyte-macrophage-derived cytokine of the IL-8 family. Partial structure, function, and expression in acute pulmonary inflammation.

BACKGROUND

Neutrophil-chemotactic peptides are a family of small basic peptides 70 to 80 amino acids in length. They contain four conserved cysteine residues, the first two spaced by one amino acid (C-X-C). The best characterized species is human IL-8. Other prominent members are melanoma growth stimulatory activity (GRO-alpha), neutrophil-activating peptide-2, and epithelial-cell derived neutrophil-activating protein 78.

EXPERIMENTAL DESIGN

Bovine monocytes and alveolar macrophages were induced by lipopolysaccaride, and a major neutrophil chemotactic activity in the supernatant was purified by cation-exchange chromatography and reversed-phase HPLC. The chemotaxin was then analyzed for biologic activity on bovine neutrophils by in vitro chemotaxis, shape change, and transient rise of intracellular-free calcium concentration. The in vivo role of bovine GRO (boGRO) was tested immunohistologically in confirmed cases of pneumonic pasteurellosis.

RESULTS

We have purified and partially sequenced a bovine homologue of human GRO-alpha. The partial amino acid sequence of boGRO was: APVVNELRCQCLQTLQGIHLKNIQSVKVTTPGP. BoGRO was biologically active and induced a dose-dependent neutrophil migration in the range of 10(-7) to 10(-9) M. BoGRO also induced a dose-dependent shape change in bovine neutrophils similar to human IL-8. This effect was detectable down to 10(-10) M. Similar effects were observed on the transient rise of intracellular-free calcium concentration. In bovine pneumonic pasteurellosis and, to a lesser extent, in normal lungs, immunoreactivity to human GRO was highly positive in hypertrophic type-II epithelial cells and in mesothelial cells, whereas pleural fibroblasts and bronchial epithelial cells were negative.

CONCLUSIONS

BoGRO is a prominent neutrophil chemoattractant secreted by monocytes and alveolar macrophages. It is active at similar concentrations as human IL-8. The strong immunoreactivity in type-II epithelial and mesothelial cells of bovine pneumonia strongly suggest a role for boGRO in the genesis of pulmonary inflammation.