Evidence that Candida albicans binds via a unique adhesion system on phagocytic cells in the marginal zone of the mouse spleen.

We recently demonstrated by using an ex vivo adhesion assay that Candida albicans yeast cells exhibit a unique binding affinity for the marginal zone of the spleen. This binding event provides a working model for studying mechanisms of organ dissemination of the fungus from the blood. By using the ex vivo assays reported here, we showed by bright-field and electron microscopic techniques that mouse spleen marginal zone cells capable of ingesting India ink particles are also involved in yeast cell attachment. During splenic clearance of yeast cells from the circulation in vivo, C. albicans is also associated exclusively with marginal zone cells capable of ingesting India ink. The ability to ingest the ink particles is not necessarily related to yeast cell adherence, because the fungal cells did not bind to phagocytic cells in the splenic red pulp. In fact, the marginal zone phagocytic cells appear to have a unique binding system, because yeast cells also did not bind to phagocytes in other tissues, such as the thymus and peritoneum, or to seven different myeloid cell lines. In addition, antibodies to a number of well-characterized murine adhesion molecules, such as leukocyte integrins, LECAM-1, and CD44, had no effect on binding. On the basis of these results, we propose that splenic marginal zone phagocytes express a novel adhesion system that involves either a unique adhesion molecule or previously described adhesion molecules with unique binding activities.