MONOCYTE CHEMOTACTIC PROTEIN-1 IN THE INFLAMMATORY PSEUDOTUMOR OF THELUNG

Inflammatory pseudotumour of the lung is a lesion mainly composed of h istiocytes. Histiocyte accumulation may arise from local proliferation of migratory cells, from cytokine induced recruitment of monocytes fr om the systemic circulation, or both. Cell proliferation was investiga ted with Ki-67 immunostaining and cytokine production with reverse tra nscriptase-polymerase chain reaction in two cases of inflammatory pseu dotumour of the lung. It was found that the two lesions were composed mainly of non-proliferating (Ki-67 non-binding) macrophages that stain ed positive for CD68, CD14, CD4, and mannose receptor. Both cases cont ained mRNA transcripts for monocyte chemotactic protein-1 (MCP-1), a m onocyte chemoattractant, and for interleukin 6 (IL-6), an inducer of p lasma cell differentiation. One of the two cases also contained mRNA t ranscripts for IL-8, a neutrophil chemoattractant. These findings are consistent with the possibility that accumulation of non-proliferating histiocytes induced by MCP-1 is one of the pathogenic events occurrin g in inflammatory pseudotumour of the lung.