E. Majewska et al., THE IMMUNOREGULATORY GRANULOCYTE FACTOR (GF) .3. CHARACTERISTICS OF TARGET-CELLS FOR GF, Journal of investigational allergology & clinical immunology, 4(2), 1994, pp. 71-80
Granulocyte factor (GF) is a substance secreted selectively from the s
pecific granules of granulocytes in the first minutes of adherence or
phagocytosis. GF possesses many immunoregulatory functions. We applied
flow cytometric analysis to evaluate the target cells responsible for
GF action. Resting lymphocytes did not display binding sites for GF,
but 93 +/- 4.6% of the neutrophils isolated from peripheral blood boun
d GF (mean fluorescence = 122 +/- 11). GF was bound by 26 +/- 7.6% of
the lymphocytes from nonstimulated and 42.6 +/- 12% of the lymphocytes
from PHA-stimulated cultures, and the mean fluorescence intensity was
14.5 +/- 1 and 54 +/- 10.6, respectively. PHA-stimulated CD8+ cells p
resented higher expression of binding sites for GF than CD4+ cells. Bi
nding sites for GF were found on 66 +/- 5.1% of activated cells expres
sing the receptor molecule to IL-2 (CD25) and 50.3 +/- 7.4% of culture
d lymphocytes expressing the early activation marker CD69. These value
s were significantly higher in comparison to the percentage of CD25- a
nd CD69- cells that bound FITC-labeled GF (10.3 +/- 3.3% and 11.3 +/-
3.5%, respectively). The binding was specific, and preincubation of th
e cells with GF almost completely abolished FITC-labeled GF binding. I
t has also been shown that GF binds to lymphocytes via molecules other
than CD 16. High-performance liquid chromatography (HPLC) with fracti
onated GF showed three separate fractions and two of them had GF-like
activity, as demonstrated in the mixed lymphocyte reaction (MLR).