Superantigenic properties of a novel mitogenic substance produced by Yersinia pseudotuberculosis isolated from patients manifesting acute and systemic symptoms.

A novel product from Yersinia pseudotuberculosis exhibiting mitogenic activity for human PBMC (designated Y. pseudotuberculosis-derived mitogen, YPM) was examined for its biologic activities for human lymphocytes. YPM induced a substantial proliferative response and IL-2 production at 0.1 ng/ml or more in whole PBMC but not in T-depleted PBMC. IL-2 production occurred within 12 h after YPM stimulation. T cells from PBMC produced IL-2 in the presence of L cells transfected with HLA DR genes or DP genes but not in the presence of control L cells used as accessory cells. Paraformaldehyde fixation did not abolish the AC activity of the DR+ L cells. The results suggest that YPM bind directly to HLA class II molecules. Analysis of the TCR V beta element using the polymerase chain reaction revealed that YPM selectively activated human T cells bearing V beta 3, V beta 9, V beta 13.1, and V beta 13.2 in TCR. These results indicate that YPM is a potent T cell activator and has superantigenic properties (abilities to bind directly to MHC class II molecules and selectively stimulate T cell populations bearing particular V beta elements in TCR). The role of YPM in the mechanism of pathogenesis of Y. pseudotuberculosis infections manifesting acute and systemic clinical symptoms is discussed.