The distribution and functional properties of dendritic cells in patients with seronegative arthritis

Abstract

SUMMARY Dendritic cells (DC), potent antigen-presenting cells, are known to be increased in numbers in inflammatory lesions in rheumatoid arthritis and juvenile chronic arthritis. In this study, patients with seronegative arthritis were studied: the distribution and functional properties of DC enriched low density cells (LDC) from peripheral blood (PB) and synovial fluid (SF) were compared. The composition of LDC from both sources was similar, comprising approximately 30% DC, 60% monocyles with few T lymphocytes. SF was significantly enriched for LDC compared with paired peripheral blood (P<0.0001) or peripheral blood from healthy controls (P < 0.00l). In contrast, patient PB contained fewer LDC (P < 0.05) overall than healthy controls. LDC from both sources were potent stimulators of allogeneic PB T cells in a mixed leucocyte reaction (MLR), but in four out of 10 patients SF LDC were significantly more stimulatory. In autologous MLRs (AMLRs) SF T cells were not stimulated by cither LDC population. This anergy of T cells was confined to the joint as patient PB T cells showed an AMLR response to PB LDC which was similar to that seen in cells from healthy controls. PB T cells also responded to SF LDC; in a minority of patients SF LDC caused significantly greater stimulation in AMLR than PB LDC and the possibility is discussed that this may represent presentation of antigen acquired in vivo.