STREPTOCOCCAL ERYTHROGENIC TOXINS INDUCE NEOPTERIN FORMATION IN HUMANPERIPHERAL-BLOOD MONONUCLEAR-CELLS BUT NOT IN THE HUMAN MYELOMONOCYTOMA CELL-LINE THP-1

We tested whether the exposure of human monocytic cells to streptococc al erythrogenic toxins A, B, C and a streptococcal-derived Mitogen EX is associated with synthesis of neopterin in vitro. Neopterin producti on was not induced when the human myelomonocytoma cell line THP-I was stimulated with these toxins, and there was only a slight costimulator y effect of streptococcal erythrogenic toxin A together with interfero n-gamma stimulation. However, these toxins induced interferon-gamma an d further neopterin production in peripheral blood mononuclear cells o f three healthy individuals. This neopterin formation could be blocked by anti-human interferon-gamma From our investigations we conclude th at there is no direct effect of streptococcal erythrogenic toxins on n eopterin production by monocytic cells. However, the data obtained in peripheral blood mononuclear cell culture imply that these toxins are able to stimulate neopterin production in humans via the induction of huge amounts of interferon-gamma.