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Circulating group II phospholipase A2 activity and antilipocortin antibodies in systemic lupus erythematosus.
W Pruzanski1, N J Goulding, R J Flower
1Inflammation Research Group, University of Toronto, Canada.
Objective:
Lipocortin (LC) and phospholipase A2 (PLA2) are involved in phospholipid metabolism, and on the cellular level LC seems to be an antagonist of PLA2. Since anti-LC1 autoantibodies were found in systemic lupus erythematosus (SLE), we undertook a study of the relationship between PLA2, anti-LC1, and disease activity in a large group of patients with SLE.
Methods:
Sera from 81 patients with SLE were tested for the activity of extracellular PLA2 and the presence and level of antilipocortin 1 [anti-LC1 (IgM) and anti-LC1 (IgG)] antibodies. Both were compared to SLE activity.
Results:
Mean PLA2 activity was 4.6-fold higher in patients with SLE than in healthy controls (707 +/- 219 vs 154 +/- 6 u/ml, p < 0.01). PLA2 activity correlated significantly with PLA2 immunoreactivity as estimated by an ELISA method using monoclonal antibodies against "synovial type" PLA2 (n = 21, r = 0.984, p < 0.001). Anti-LC1 IgM and IgG antibody levels were significantly higher in SLE than in healthy individuals [anti-LC1 (IgM) 54.5 +/- 4.6 vs 22.6 +/- 2.3 EU/ml, p < 0.001 and anti-LC1 (IgG) 54.3 +/- 3.4 vs 22.9 +/- 2.3 EU/ml, p < 0.001]. There was no correlation between PLA2 activity and anti-LC1 antibody titers. Elevated levels of PLA2 [> normal mean + 2 SD (i.e., > 300 u/ml)] were found in 41/81 patients with SLE. Anti-LC1 antibody titers were high (> 64 EU/ml) in 23/41 patients; 14/40 patients with SLE with normal PLA2 (< 300 u/ml) also had higher titers of anti-LC1 antibodies. PLA2 activity was significantly associated with the presence of synovitis, being markedly increased in 11/12 patients. Mean PLA2 in this group of patients (1593 +/- 957 u/ml) was significantly higher (p < 0.001) than that (553 +/- 188 u/ml) in the group of 69 patients with SLE without synovitis.
Conclusions:
There was no correlation of PLA2 activity with the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) or the Lupus Activity Criteria Count (LACC). Circulating PLA2 activity in SLE correlated only with active synovitis. There was no correlation of anti-LC1 titers with duration of the disease, age, steroid dosage, SLEDAI, or LACC or any individual clinical or laboratory variable included in the assessment of SLEDAI and LACC.