BDNF and systemic lupus erythematosus: NGF, BDNF and NT-3 concentrations were similar in SLE patients with or without secondary Sjögren’s syndrome (NGF 430.7 ± 113.2 vs 424.5 ± 51.8 pg/mL, BDNF 624.27 ± 102.31 vs 589.4 ± 139.89 pg/mL, NT-3 3094.86 ± 1262.33 vs 2860.87 ± 1274.52 pg/mL, all NS).