RESTRICTED EXPRESSION OF GALACTOSE N-ACETYLGALACTOSAMINE-SPECIFIC MACROPHAGE C-TYPE LECTIN TO CONNECTIVE-TISSUE AND TO METASTATIC LESIONS IN MOUSE LUNG/

We investigated expression of macrophage galactose/N-acetylgalactosami ne-specific C-type lectin (MMGL) in normal mouse lung tissue and in lu ngs with metastatic nodules produced by OV2944-HM-1 mouse metastatic o varian tumour cells. Cells expressing MMGL were detected in tissue sec tions using a rat monoclonal antibody (mAb) specific for MMGL, mAb LOM -14. The regions containing cells immunostained using mAb LOM-14 were restricted to the connective tissue surrounding blood vessels and resp iratory epithelia, whereas alveolar regions of lung parenchyma were es sentially devoid of these cells. In contrast, a significant number of cells in the alveolar regions was shown to express Mac-1 antigen (CD11 b/CD18) and leucocyte common antigen (CD45). Immunoelectron microscopi c study revealed the presence of MMGL in the intracellular vesicles of cells residing in connective tissue. In the tumour-bearing mice, MMGL -positive cells were also present within metastatic nodules. Their loc alization outside of the nodules was restricted to connective tissue. Cells with Mac-1 antigens were seen both in the nodules and in the alv eolar regions. These results indicate that MMGL serves as a unique mac rophage marker in mouse lung tissue due to its topographical site-depe ndent pattern of expression. The present results also suggest a possib le involvement of macrophages expressing MMGL in the immune response d irected against metastatic tumour cells.