Suppressive effect of intravenous immunoglobulins on the activity of interleukin-1

In order to study the effect of human immunoglobulin preparations for intravenous use (IVIg) on the production and activity of interleukin-1 (IL-1) derived from monocytes, we treated cultured monocytes with IVIg and examined the lymphocyteactivating factor (LAF) activity of IL-1 in the culture supernatants. The results showed that IVIg suppressed the activity from most healthy adults and some febrile children with acute respiratory disease or Kawasaki disease. Further studies revealed that intact Ig (whole molecular Ig) did not suppress the mRNA expression of IL-1α or IL-1β in mononuclear cells, that intact Ig and pepsin-digested Ig inhibited the LAF activity of recombinant IL-1 (rIL-1) and also that intact Ig contains immunoglobulin (probably anti-IL-1 antibody) which binds with rIL-1 by dot blotting using biotin-streptavidin. These results suggest that IVIg suppresses neither IL-1 synthesis nor the release of IL-1 from monocytes but does neutralize IL-1α and IL-1β activity by binding IL-1 proteins as an anti-IL-1 antibody.