Expression of tumour necrosis factor receptors (CD120a and CD120b) on bronchoalveolar cells

It is generally accepted that physiological modulators for tumour necrosis factor (TNF) are present in a variety of body fluids including serum. Among these modulators are soluble TNF receptors (TNF-R) that are cleaved from the extracellular domain of the TNF-Rs. Two receptors of different structures with molecular weights of 55 kDa (CD120a) and 75 kDa (CD120b) are known to be expressed on monocytes, lymphocytes, granulocytes and other cells of peripheral blood. The aim of our study was to determine the expression of CD120a and CD120b on bronchoalveolar lavage cells (BAL cells). BAL cells of 14 patients with different pulmonary disorders were stained with anti-CD120a and anti-CD120b monoclonal antibodies and were differentiated by FACS analysis. Both TNF-Rs are expressed on monocytes, macrophages, lymphocytes and granulocytes of the BAL. Although the relation of CD120a to CD120b is individual for a given cell type and an individual patient, strict correlations between both receptors were observed for BAL monocytes and alveolar macrophages. CD120a are expressed on 29.7% of alveolar macrophages; similar data were obtained for CD120b. 24.3% of the BAL monocytes were positive for CD120a and 25.5% for CD120b. 4.1% of the BAL lymphocytes were positive for CD120a whereas the percentage of CD120b positive BAL lymphocytes was approximately six times greater. Analysis of BAL granulocytes revealed 21.2% cells positive for CD120a and 11.6% for CD120b. In contrast to the BAL cells named above there was no positive correlation between CD120a and CD120b expression on BAL lymphocytes and granulocytes. We were able to show that TNF-Rs of BAL cells, like those of blood cells, are shedded in vitro after incubation with or without lipopolysaccharide (LPS), detected as TNFalpha-inhibitor activity in cell culture supernatant. In conclusion, BAL cells express and shed TNF-Rs, as is known for cells of other body compartments.