SSB/
La antigen, expressed on surface of polymorphonuclear neutrophils (PMN), is one of the cognate
antigens recognized by antineutrophil
antibodies. The present study was aimed to assess PMNs in
systemic lupus erythematosus (SLE) patients for their phagocytic efficiency and its correlation with history of
infections and presence of anti-SSB/La
antibodies and their capacity to produce
interleukin (IL)-12 in response to
lipopolysaccharide (LPS) with or without
interferon gamma (IFN-gamma). Fifty patients with SLE, fulfilling American College of Rheumatology criteria of diagnosis, and 20 healthy controls were enrolled for the study. Phagocytic efficiency was evaluated by flow cytometry, using flourescein
isothiocyanate (
FITC)-labeled Escherichia coli, and expressed as mean channel fluorescence (MFI). PMNs were stimulated with LPS or LPS + IFN-gamma for 18 h,
IL-12p40 was estimated in supernatants by
enzyme-linked
immunosorbent assay, and anti-SSB/La
antibodies were detected in serum by Western blot. The mean MFI values were significantly lower in patients with SLE than controls (P < 0.0001), and among patients, it was lower in patients with history of
infection than in those without (P < 0.005). Anti-SSB/La positivity was also associated with lower MFI (P < 0.005) and higher frequency among patients with history of infective episodes (P < 0.05). LPS- and LPS + IFN-gamma-stimulated
IL-12 levels were lower among SLE patients than in controls. However, there was no difference in the levels of
IL-12 between patients with and without history of
infection. These data suggest that the
autoantibodies to SSB/La may modulate PMN function in SLE.