MOBILITY OF HUMAN NEUTROPHILS IN RESPONSE TO CRYPTOCOCCUS-NEOFORMANS CELLS, CULTURE FILTRATE ANTIGEN, AND INDIVIDUAL COMPONENTS OF THE ANTIGEN

The mobility of human neutrophils (PMN) in response to encapsulated or nonencapsulated Cryptococcus neoformans cells or cryptococcal culture filtrate (CneF) and its components was studied by using a 48-well mod ified Boyden chamber. Encapsulated C. neoformans (isolate 184A) cells and CneF-184A stimulated directed migration of human PMN in the absenc e of serum (direct chemotactic activity) and activated a heat-labile c omponent(s) in fresh human serum to become a chemoattractant(s) for hu man PMN (indirect chemotactic activity). At a 1:8 dilution (0.25 mg of carbohydrate per ml), CneF-184A displayed chemokinetic activity when assessed with a checkerboard assay. Nonencapsulated C. neoformans isol ate 602 cells did not have direct chemotactic activity but did have in direct chemotactic activity. The capsule of C. neoformans is composed predominantly of glucuronoxylomannan (GXM). Purified GXM displayed bot h direct and indirect chemotactic activity. CneF-184A contains, in add ition to GXM, a concanavalin A-binding mannoprotein (MP), whereas CneF -602 contains no GXM but does contain MP. CneF-184A showed direct chem otactic activity and CneF-602 did not. Both CneF-184A and CneF-602 dis played indirect chemotactic activity for human PMN. In addition, purif ied MP from CneF-184A, like CneF-602, showed only indirect chemotactic activity. These results indicate that GXM contributes to the direct c hemotactic activity of PMN observed with the whole encapsulated yeast cells and the unfractionated CneF derived from the encapsulated cells. Both MP and GXM from encapsulated C. neoformans cells mediate indirec t chemotactic activity on human PMN.