Natural killer cell activity and frequency of killer cell immunoglobulin-like receptors in children with different forms of juvenile idiopathic arthritis

BackgroundJuvenile idiopathic arthritis (JIA) has three major onset types with widely varying clinical features: systemic, polyarticular and pauciarticular. We assessed natural killer (NK) cell function and killer cell immunoglobulin-like receptor (KIR) genotypes in patients with different JIA subtypes. MethodsPeripheral blood samples from 72 children with active JIA (systemic, 25; polyarticular, 24; pauciarticular, 23) and 25 controls were used for flow cytometric assessments of NK cell count, cytotoxicity, perforin, granzyme B, interferon (IFN)- and tumour necrosis factor (TNF)-. Samples from 220 children with JIA (systemic, 84; polyarticular, 72; pauciarticular, 64) and 150 controls were used for KIR2DS2, KIR2DS4, KIR3DS1, KIR2DL1, KIR2DL2, KIR2DL3 and KIR3DL1 typing by polymerase chain reaction with sequence-specific oligonucleotide probes. ResultsCompared with the controls, the patients with systemic JIA showed lower NK cell counts, cytotoxicity and perforin and granzyme B expression (p<0.05), while the patients with pauci- and polyarticular JIA showed higher perforin and granzyme B expression (p<0.05). NK cells produced higher level of TNF- while lower level of IFN- in the pauci- and polyarticular JIA groups than in the systemic JIA group (p<0.05). No significant differences in KIR gene frequencies were found between the JIA subgroups and healthy controls, except for the positive frequency and locus frequency of KIR2DS4, which were lower in the systemic JIA group. ConclusionsCompared with poly- and pauciarticular JIA, systemic JIA is associated with decreased NK cell function, more IFN- and less TNF- secretion of NK cell and lower KIR2DS4 frequency.