Diurnal variation of immunosuppressive acidic protein.

Diurnal variations of serum immunosuppressive acidic protein (IAP) were studied in four healthy individuals and in four patients with complete type Behçet's disease with active uveitis. The circadian rhythm of the serum level of the protein was recognized in both groups. The peak value was at 1800 hours in the healthy subjects and at 2200 hours in those with Behçet's disease. Although the exact mechanism underlying the rhythmic variation in this clinical marker of acute phase reaction is unknown, the close interaction between the immune system and the rhythmicity of corticosteroids should be considered. The data also suggest that the time of day when sampling is carried out should be considered when evaluating the levels of IAP.