The ontogeny of a 57-Kd cationic antimicrobial protein of human
polymorphonuclear leukocytes: localization to a novel granule population
HA Pereira, JK Spitznagel, EF Winton, WM Shafer, LE Martin, GS Guzman, J Pohl, RW Scott, MN Marra and JM Kinkade
Department of Microbiology, Emory University School of Medicine, Atlanta,
GA.
The ontogeny of a 57-Kd cationic antimicrobial protein (CAP57) that has
substantial similarities to bactericidal permeability increasing protein
(BPI) has been determined immunocytochemically. CAP57 was detected in the
granules of mature peripheral blood neutrophils. However, it was absent
from other cells of the peripheral blood: eosinophils, red blood cells
(RBCs), and mononuclear cells. In human bone marrow, CAP57 was confined to
the neutrophilic series. The earliest stage of development of the myeloid
cells at which CAP57 was demonstrated was the promyelocyte. Double
immunofluorescent labeling showed that CAP57 was detected in cells positive
for myeloperoxidase. The absence of lactoferrin in certain cells
(promyelocytes) containing CAP57 indicated that CAP57 was synthesized and
packaged in a population of granules prior to the development of granules
that contain lactoferrin. CAP57 could not be demonstrated in HL60 cells
either by enzyme-linked immunosorbent assay (ELISA) or by
immunocytochemistry. However, the presence of another granule-associated
cationic antimicrobial protein of molecular weight 37 Kd (CAP37) was
readily detected in undifferentiated HL60 cells. Amino acid sequence
analysis showed that CAP57 and BPI were identical. Further indication of
the identity between CAP57 and BPI was that monoclonal anti-CAP57
antibodies cross reacted with BPI. Sucrose density-gradient centrifugations
showed CAP57 was confined to a granule population that exhibited a buoyant
density intermediate of the previously described light and heavy azurophil
granules. Further resolution of the individual azurophil granule
populations by Percoll density-gradient centrifugation revealed that CAP57
was most concentrated in the density range of 1.093 to 1.100 g/cc. These
results strongly suggest the unique finding that CAP57 may be associated
with a heretofore unreported granule type.
Volume 76,
Issue 4,
pp. 825-834,
08/15/1990
Copyright © 1990 by The American Society of Hematology
