Immunological aspects of polymyalgia rheumatica and giant cell arteritis

Forty four patients with PMR/GCA have been followed from presentation for a period of 2-4 years. Immunological investigations have been carried out in a search for useful tests to assist in the diagnosis of PMR/GCA and in assessing disease activity. This study has confirmed that ESR and CRP are useful investigations at presentation of PMR/GCA, although even at this stage these tests may not be elevated. During relapses of PMR/GCA both ESR and CRP remain in the normal range in the majority of patients so no reliance should be placed on these investigations to confirm a clinical diagnosis of relapse. Alpha-1-antichymotrypsin (ACT) has shown an interesting pattern of response, in that the raised levels at presentation (1.0g/l) did not fall rapidly on prednisolone treatment but fell gradually over 2-4 years reaching normal levels (0.6g/l) in those patients satisfactorily off prednisolone treatment. An ACT concentration of ≤0.8g/l at 12 months and ≤0.7g/l at 18 months indicated a reduced risk of subsequent relapse. Hence this investigation may be a useful tool in tailoring prednisolone reduction for the individual patient with PMR/GCA. Measurement of the cytokines IL1B, IL6 and soluble IL2 receptor, using ELISA methods, did not add any useful information to the assessment of the individual patient. However the fact that IL1≤ levels were raised at presentation and relapse (albeit to only 4pg/ml and 5pg/ml respectively) does illustrate that this mediator of inflammation is involved in PMR/GCA. The elevation of soluble IL2 receptor at presentation (476 U/ml) compared with controls (366 U/ml) also illustrates that there is immune system activation in PMR/GCA. IL6 levels were not significantly elevated in this study. This study did not find low CD8+ cells in PMR/GCA prior to treatment. %CD8+ cells were significantly reduced after prednisolone treatment commenced, and a study in volunteers confirmed that this was an effect of the prednisolone itself, particularly in the older volunteers