D. Vitolo et al., RAPID IL-2-INDUCED ADHERENCE OF HUMAN NATURAL-KILLER-CELLS - EXPRESSION OF MESSENGER-RNA FOR CYTOKINES AND IL-2 RECEPTORS IN ADHERENT NK-CELLS, The Journal of immunology, 151(4), 1993, pp. 1926-1937
Natural killer (NK) cells selected by IL-2-induced rapid adherence to
plastic and called A-NK cells represent a phenotypically and functiona
lly distinct subset of mature peripheral blood NK cells. To further ch
aracterize this subset of NK cells functionally, their potential to ex
press mRNA for the IL-2R and various cytokines after IL-2 activation w
as examined. Highly purified normal human peripheral blood resting NK
(R-NK) cells were obtained by negative immunoselection using OKT3 mAb
and magnetic beads coated with goat anti-mouse Ig. By two-color flow c
ytometry, >90% of these R-NK cells were either CD3-CD56+CD16+ or - or
CD3-CD56-CD16+. R-NK cells were activated in the presence of 6000 IU/m
l (22 nM) of IL-2 for different periods of time. After 1, 3, 5, or 24
h, plastic-adherent (A) and nonadherent (NA) NK cells were separated a
nd compared for the expression of the IL-2R or cytokine mRNA by in sit
u hybridization, using [S-35]-cDNA probes. Only low proportions of R-N
K cells expressed genes for IL-2Rp55 (16%) or cytokines IL-2 (20%), IF
N-gamma (18%), TNF-alpha (16%), and TGF-beta (7%). Thus, the genes for
the IL-2Rp55 and these cytokines were not constitutively expressed by
most human R-NK cells, and there was no indication that the NK cells
used in these experiments were activated in vivo or during the purific
ation procedure. However, larger proportions of R-NK cells showed expr
ession of mRNA for IL-1-beta (35%) and IL-6 (40%), which indicates tha
t genes for these cytokines may be constitutively expressed in a subst
antial proportion of normal human circulating NK cells. When R-NK cell
s were incubated in the presence of 22 nM of IL-2 for 1 to 24 h and se
parated into A-NK cells and NA-NK cells, a large proportion of A-NK ce
lls became positive for IL-2R and cytokine gene expression. In contras
t, the proportion of mRNA-positive NA-NK cells was similar or lower th
an that observed for R-NK cells, with the exception of an increase in
TGF-beta. Thus, significantly higher proportions of A-NK than NA-NK ce
lls expressed mRNA for the IL-2Rp75 (e.g, at 3 h after induction with
IL-2, 58% vs 12%), IL-2Rp55 (at 5 h, 74% vs 4%), IL-2 (at 5 h, 68% vs
10%), TGF-beta (at 5 h, 82% vs 30%), IL-1-beta (at 5 h, 80% vs 24%) an
d IL-6 (at 5 h, 79% vs 34%). Message for TNF-alpha or IFN-gamma was ex
pressed in a high proportion of both A-NK and NA-NK cells (at 3 h, 70%
and 64% for TNF-alpha and 58% and 30% for IFN-gamma, respectively). T
he increased mRNA expression in A-NK cells at 3 h was followed by high
levels of release of the proteins in 48 h culture supernatants. As ex
pected, A-NK cell supernatants contained considerably higher levels of
sIL-2R, IL-2, and IL-1-beta than those of NA-NK cells. In contrast, N
A-NK cell supernatants contained more IFN-gamma than those of A-NK cel
ls. Both subsets of NK cells produced similar levels of TNF-alpha. The
data indicate that A-NK cells are a subset of NK cells that have not
only been rapidly altered in their adherence properties, but also have
a high level of NK activity and are selectively activated for express
ion of IL-2R and several cytokine genes. Thus, A-NK cells appear to re
present both a rapidly adherent and activated subset of NK cells.