An assessment of peripheral immunity in patients with sarcoidosis using measurements of serum vitamin D3, cytokines and soluble CD23.

The aetiology of the peripheral anergy in sarcoidosis is unclear. To investigate this further we measured the serum levels of several factors important in different aspects of immune regulation to obtain a profile of those factors which promote and inhibit immune activation in sarcoidosis. Thirty-seven patients with sarcoidosis and 20 healthy controls of similar sex and age comprised the study group. Serum IL-10, interferon-gamma (IFN-gamma), soluble CD23 (sCD23), IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-1beta and tumour necrosis factor-alpha (TNF-alpha) were measured using in-house ELISAs. Vitamin D3 was measured using a radioreceptor assay. Serum levels of sCD23 and IL-10 were significantly elevated in patients with sarcoidosis relative to controls (median 13.9 versus 9.5 arbitrary units/ml, P<0.01 for sCD23, and 9.6 versus 5.0 pg/ml, P<0.04 for IL-10). Regardless of steroid therapy or disease activity, serum levels of IFN-gamma, TNF-alpha, IL-1beta, GM-CSF and IL-8 were no different in patients with sarcoidosis and controls. Vitamin D3 levels were significantly higher in patients with sarcoidosis versus normal controls (medians 78.0 versus 56.0, P<0.001), active sarcoidosis (n = 20) versus inactive disease (n = 17) (medians 81.5 versus 66.0, P<0.03) and active sarcoidosis versus controls (medians 81.5 versus 56.0, P<0.0002). The levels were no different between patients with inactive sarcoidosis and controls. We suggest that IL-10 and vitamin D3 may contribute to the peripheral anergy in sarcoidosis. The elevated serum sCD23 suggests an increase in peripheral humoral immunity. Consistent with a quiescent peripheral immune system, factors capable of monocyte/macrophage activation (TNF-alpha, IFN-gamma, GM-CSF and IL-8) were not elevated in the peripheral circulation.