A sensitive and specific bioassay for the detection of human interleukin-10

Interleukin-10 (IL-10) is a novel cytokine that is produced by T cells, macrophages, B cells and keratinocytes. It has been shown to inhibit cytokine production and proliferation by T cells when macrophages are used as accessory or antigen presenting cells. Monokine production by macrophages is effectively downregulated by IL-10 and it can be used as a growth factor by CD4, CD8 and gamma/delta positive T cells as well as mast cells and B cells. It is because of these pleiotropic immunoregulatory effects that the detection of IL-10 in the supernatants of T cells, B cells, macrophages and other cells is important for many scientific questions. Here we describe a simple and sensitive bioassay specific for human IL-10 using the IL-10 dependent growth of the mouse mast cell line D36. Our data show that this assay is not crossreactive with hIL-1 beta, hIL-2, hIL-3, hIL-4, hIL-5, hIL-6, hIL-9, hIL-12, hGM-CSF and hTNF-alpha and that it can be completely blocked by an antibody against human IL-10. The hIL-10 induced growth of the D36 cell line is dependent on the presence of mIL-4. Human IL-10 can be measured in a concentration range from approximately 10 U/ml to 0.05 U/ml. This assay is only of limited use for the measurement of IL-10 in human blood samples since it is inhibited by the presence of human serum.