Cell biology of echinoid coelomocytes. 1. Diversity and characterization of cell types

Echinoderm (Strongylocentrotus ) coelomocytes have been postulated to play an important role in cell-mediated host defense mechanisms. The diversity and classification of coelomocyte types has been underestimated and therefore any assignment of cell types to specific role has been incomplete. Evidence is presented that the petaloid, phagocytic cell type is composed of two distinctive subsets of cells. The two subsets differ in their position on sucrose gradients following their isolation, in their tendency to aggregate, and in their shape and appearance when spread on a glass substratum, and the structure and composition of the actin-based cytoskeleton is different in each subset. The relative role of each subset in host defense mechanisms may be reflected in these differences.