INDUCTION OF BETA(2) INTEGRIN-DEPENDENT NEUTROPHIL ADHESION TO HUMAN ALVEOLAR EPITHELIAL-CELLS BY TYPE-1 STREPTOCOCCUS-PNEUMONIAE AND DERIVED SOLUBLE FACTORS

Pneumonia caused by Streptococcus pneumoniae is characterized by neutr ophil infiltration and variable epithelial injury, Neutrophil adhesion to alveolar epithelial pneumocytes (A549) was measured and demonstrat ed to be dose-dependent following preincubation of these (A549) pneumo cytes with type 1 S. pneumoniae. Adhesion peaked at a bacteria-to-epit helial cell ratio of 5:1 after a 4-h incubation but was absent after 2 h and without FMLP. Filtered conditioned media (CM) from pneumococci cultured with (CM+) or without (CM-) epithelial cells were tested. CM induced significant adhesion in the absence of FMLP (P <.001); CM- ha d no effect, In the presence of FMLP, adhesion induced by both media w as significantly greater than by FMLP alone (P <.001) and was signific antly blocked (P <.01) by antibodies to CD11b and CD18. CM+ upregulate d epithelial intercellular adhesion molecule 1 but CM- did not. These data provide new information concerning the interactions of S. pneumon iae, alveolar epithelial cells, and neutrophils.