T. Darville et al., INTRAVENOUS IMMUNOGLOBULIN MODULATES HUMAN MONONUCLEAR PHAGOCYTE TUMOR-NECROSIS-FACTOR-ALPHA PRODUCTION IN-VITRO, Pediatric research, 35(4), 1994, pp. 397-403
Mononuclear phagocytes (MO) secrete tumor necrosis factor-alpha (TNF)
in response to inflammatory stimuli most notably the bacterial product
lipopolysaccharide (LPS). Cross-linking of MO Fc receptors also induc
es TNF release. Immunoglobulin for i.v. use is currently being investi
gated for the treatment and prophylaxis of neonatal sepsis and for the
treatment of various syndromes of autoimmune dysfunction in children
and adults. We examined the in vitro effect of immunoglobulin-gamma (I
gG) on neonatal (cord blood) monocyte and adult MO TNF production. Kin
etic studies were performed on MO incubated with IgG alone and on MO p
reincubated with IgG and stimulated with interferon-gamma/LPS. Incubat
ion of MO in IgG (1-25 g/L) for 2, 6, and 24 h did not stimulate TNF s
ecretion or production. However, enhanced TNF secretion was detected i
n MO preincubated in IgG and subsequently stimulated with interferon-g
amma/LPS. TNF secretion by cord blood monocytes was increasingly enhan
ced by preincubation for 6 h with 1, 10, and 25 g/L IgG (2413.1 +/- 13
89.4, p < 0.05; 4070.4 +/- 3069.2, p < 0.005; and 6383.7 +/- 2982.2, p
< 0.005 versus 1215 +/- 575.9 ng/L, respectively, in cells preincubat
ed in medium alone). Significant enhancement was also detected in cord
blood monocytes preincubated in IgG for 2 h. TNF secretion by adult M
O was similarly enhanced (6082.0 +/- 1732.8, p < 0.05; 7158.8 +/- 3938
.2, p < 0.05; and 7302.7 +/- 3451.4, p < 0.05 versus 3353.2 +/- 2946.7
ng/L for 1, 10, and 25 g/L IgG, respectively, versus preincubation in
medium alone). In additional experiments performed with Fc, Fab, and
F(ab')(2) fragments, only F(ab')(2) fragments yielded positive results
. Northern analyses revealed increased levels of mRNA for TNF only whe
n 25 g/L IgG were used for preincubation. Preincubation in the lower c
oncentrations of IgG did not result in increased accumulations of TNF
mRNA. Thus, IgG acts primarily posttranscriptionally to enhance interf
eron-gamma/LPS-induced TNP release in vitro.