Distinctive effects of G-CSF, GM-CSF and TNFalpha on neutrophil apoptosis in systemic lupus erythematosus

To investigate the influence of culture with G-CSF GM-CSF and TNFalpha on neutrophil apoptosis, comparing neutrophils from SLE patients with rheumatoid arthritis (RA) patients and healthy control subjects.

Neutrophils were isolated from SLE (n= 10), RA (n= 10) and healthy control subjects (n= 10), and cultured with two different concentrations of G-CSF, GM-CSF and TNFalpha. Proportion of apoptotic neutrophils at T=0, T=2hrs and T=24hrs was measured using FITC-labelled annexinV and flow cytometry.

Significantly more neutrophils were apoptotic at T=0 in the SLE subjects than in the other groups (median, range--Control 3.5% (0.3-7.9) SLE 9.5% (2.9-29.1) RA 3.0% (0.4-23.0) p<0.05). Following culture for 24 hours with 1ng/ml G-CSF the proportion of apoptotic neutrophils from SLE subjects was significantly increased (median, range = 51.6% (27.0-84.0) without G-CSF v 66.8% (31.8-89.2) with G-CSF p<0.05). This was not observed with RA or control subjects, in whom the trend was towards inhibition of apoptosis. Similar trends were seen with GM-CSF There was significant induction of apoptosis in SLE neutrophils after 2 hr culture with 1ng/ml TNFalpha (median, range = 2.3% (0.1-8.0) without TNFalpha v 5.2% (1.0-22.4) with TNFalpha). No significant change was seen in the other groups. There was an inverse correlation between total neutrophil count and the degree of induction of apoptosis by G-CSF and GM-CSF, determined at a range of time-points and cytokine concentrations

Neutrophils from SLE patients display resistance to the apoptosis-inhibiting effects of G-CSF and possibly GM-CSF, and appear more susceptible to the apoptosis-inducing action of TNFalpha, the greatest resistance being observed in the more neutropenic patients.