Endotoxin-associated protein: a potent stimulus for human granulocytopoietic activity which may be accessory cell independent.

Proteins coextracted with endotoxin, termed endotoxin-associated protein (EAP), have been shown to exert interleukin 1-like activities. The present studies demonstrate that EAP also exerts potent granulopoietic colony-stimulating activity (CSA) on human peripheral blood and bone marrow progenitor cells, comparable to that seen with various types of conditioned media. The CSA observed with EAP appeared to be heat (100 degrees C, 30 min) and trypsin resistant and partially pronase resistant. Similar resistance was observed with the porin proteins of the outer membrane of gram-negative bacteria, and similar CSA activity was observed with a purified porin preparation of Neisseria gonorrhoeae. The CSA of EAP could be demonstrated in human peripheral blood and bone marrow leukocytes rigorously depleted of monocytes, T lymphocytes, and B lymphocytes by treatment with specific monoclonal antibodies and complement.