Small-vessel vasculitis surrounding an uninflamed temporal artery and isolated vasa vasorum vasculitis of the temporal artery: two subsets of giant cell arteritis

NKG2D stimulated T-cell autoreactivity in giant cell arteritis and polymyalgia rheumatica

OBJECTIVE

To investigate functional expression of NKG2D on CD4 and CD8 T-cells in patients with giant cell arteritis (GCA) and polymyalgia rheumatica (PMR).

METHODS

Peripheral blood was drawn from patients with GCA (n=16), PMR (n=78) and healthy controls (HC, n=64). Tissue samples were obtained from GCA patients and controls. Proliferation and cytokine production assays were performed using CFSE and intracellular IFN-γ or TNF-α staining, respectively, and flow cytometry analysis. Immunofluorescence and immunohistology were applied to analyse the presence of NKG2D-expressing T-cells and NKG2D-ligands in temporal arteries, respectively. mRNA levels of NKG2D-ligands were determined by RT-PCR.

RESULTS

In both GCA and PMR patients, NKG2D was preferentially expressed on senescent CD4CD28(-) and CD8CD28(-), as well as on CD8CD28 T-cells. Frequencies of senescent T-cells were increased in GCA and PMR patients compared to HC. In GCA tissue samples, infiltrating T-cells were predominately CD28(-). NKG2D expressing T-cells concentrated around the vasa vasorum of the adventitia. Antigenic stimulation induced rapid up-regulation of NKG2D on CD4CD28(-) and CD4CD28 T-cells, whereas TNF-α and interleukin-15 enhanced NKG2D expression on senescent CD4 and CD8 T-cells only. NKG2D cross-linkage augmented anti-CD3 triggered proliferation, IFN-γ and TNF-α production of CD8 T-cells. In CD4CD28(-) T-cells, NKG2D ligation resulted in increased IFN-γ production only. NKG2D ligands were expressed in temporal arteries from GCA patients, particularly in the adventitial and medial layers of affected vessels.

CONCLUSIONS

NKG2D is functionally expressed on CD4CD28(-) and CD8 T-cells in GCA and PMR. NKG2D-ligands are present in temporal arteries and may co-stimulate NKG2D expressing T-cells.

CC chemokine receptor 5 polymorphism in Italian patients with giant cell arteritis

OBJECTIVES

To evaluate the potential role of CC chemokine receptor 5 (CCR5)Δ32 polymorphism in the susceptibility to giant cell arteritis (GCA) in a cohort of Italian patients.

METHODS

176 consecutive Italian patients with biopsy-proven GCA and 180 healthy age- and sex-matched blood donors were molecularly genotyped for the CCR5Δ32 polymorphism.

RESULTS

No statistically significant difference in the Δ32CCR5 allele frequency between GCA patients (5.1 %) and controls (2.8 %) was observed (p = 0.109). Carriers of the CCR5Δ32 allele (Δ32/Δ32 + CCR5/Δ32) were similarly represented in the two groups.

CONCLUSIONS

Our results do not support a role for the CCR5Δ32 polymorphism in determining susceptibility to GCA.

Clinical features of polymyalgia rheumatica and giant cell arteritis

Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are inflammatory diseases that typically affect white individuals >50 years. Women are affected ∼2-3 times more often than men. PMR and GCA occur together more frequently than expected by chance. The main symptoms of PMR are pain and stiffness in the shoulders, and often in the neck and pelvic girdle. Imaging studies reveal inflammation of joints and bursae of the affected areas. GCA is a large-vessel and medium-vessel arteritis predominantly involving the branches of the aortic arch. The typical clinical manifestations of GCA are new headache, jaw claudication and visual loss. PMR and GCA usually remit within 6 months to 2 years from disease onset. Some patients, however, have a relapsing course and might require long-standing treatment. Diagnosis of PMR and GCA is based on clinical features and elevated levels of inflammatory markers. Temporal artery biopsy remains the gold standard to support the diagnosis of GCA; imaging studies are useful to delineate large-vessel involvement in GCA. Glucocorticoids remain the cornerstone of treatment of both PMR and GCA, but patients with GCA require higher doses. Synthetic immunosuppressive drugs also have a role in disease management, whereas the role of biologic agents is currently unclear.