Expression of immunoglobulin-like transcript 4 as an inhibitory receptor in patients with psoriatic arthritis

Objectives: To investigate the presence of immunoglobulin-like transcript (ILT)4 and costimulatory proteins (CD40, CD80 and CD86), as well as tumour necrosis factor (TNF)-α production in antigen-presenting cells (APCs) from patients with psoriatic arthritis, before and after treatment with the antitumour necrosis factor-α therapy, adalimumab. Methods: Peripheral blood monocytes from patients with psoriatic arthritis and healthy controls were cultured with CD40 ligand (CD40L) to stimulate differentiation to APCs. Cell-surface phenotype was analysed via fluorescence-activated cell sorting. Results: CD40L-stimulation resulted in significantly more ILT4+ monocytes in cultures from control subjects (n = 21) than those from patients (n = 20). ILT4-positivity on CD40L-stimulated monocytes was negatively correlated with disease activity in patients. Adalimumab treatment resulted in significant increases from baseline in ILT4-positivity, and in decreases in CD40, CD80 and CD86-positivity in monocytes from patients. Conclusion: The effect of adalimumab on monocyte surface phenotype may be due to modification of the inflammatory milieu associated with therapy-induced reduction of disease activity in psoriatic arthritis.