SURFACTANT PREVENTS QUARTZ INDUCED DOWN-REGULATION OF COMPLEMENT RECEPTOR-1 IN HUMAN GRANULOCYTES

Quartz is known to induce an inflammatory response in the alveolar spa ce by recruitment of different effector cells. We investigated the int eraction between granulocytes and quartz with respect to expression of complement receptor type 1 (CR1) and CR3, with and without the presen ce of surfactant. Granulocytes from hemolyzed blood were stimulated by N-formyl-methionyl-leucyl-phenylalanine (fMLP), which mobilize the in tracellular pool of CR1 to the surface, and the mean fluorescence inte nsity (MFI) measured by cytofluorometry was 47.4 (46-63.6) (median; in terquartile range). Quartz exposure reduced the CR1 expression to 23.2 (22.8-30.6) MFI units (P < 0.01), a porcine surfactant preparation ad ded during quartz exposure abolished the down-regulation completely. 4 7.7 (43.2-62.3) MFI units (P < 0.001). Similar results were obtained a fter preincubation of the cells with surfactant followed by quartz exp osure. No significant influence on CR1 expression was found by a synth etic lipid mixture, nor was the CR3 expression affected. In conclusion , this study demonstrates that the presence of surfactant inhibits qua rtz induced down-regulation of CR1 on activated granulocytes.