Although autoantibodies to interleukin-1α (IL-1α autoantibodies) are known to be present in sera of apparently healthy humans, their frequency of occurrence and significance are unclear. To determine the prevalence of detectable IL-1α autoantibodies in normal human blood, we screened the plasma of blood donors (6290 subjects : 3977 men and 2313 women, ages 16 to 64 yr) by a radioimmunoassay which we developed using a method that could detect over 5 ng/ml. Moreover, we investigated immunoglobulin class of IL-1α autoantibodies and also their function. IL-1α autoantibodies were detected in 14.6% of the 6290 donors. Their frequency was higher in males than females (16.6% vs.11.2%, p<0.01) and increased with age in both sexes. The proportion of subjects with a high IL-1α autoantibodies titers also increased with age. We showed that IL-1α autoantibodies were of the IgG class and that they had neutralizing function to IL-1α by receptor assay. Neutralizing activity was only shown in plasma with concentration of IL-1α autoantibodies, the level of which was over 1000 ng/ml. The affinity of the IL-1α autoantibodies in plasma was between 2.1 X 10-10and 1.2 X 10-9 M (mean 6.4 X 10-10M). Our results provide a basis for comparison with IL-1α autoantibodies prevalence between healthy states and disease states, and suggest that IL-1α autoantibodies may play a significant role in modulating the effects of excessive IL-1α at local site or in systemic regions
