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 mito gen, YPM) was examined for its biologic activities for human lymphocyt es. YPM induced a substantial proliferative response and IL-2 producti on 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 P BMC produced IL-2 in the presence of L cells transfected with HLA DR g enes or DP genes but not in the presence of control L cells used as ac cessory cells. Paraformaldehyde fixation did not abolish the AC activi ty of the DR+ L cells. The results suggest that YPM bind directly to H LA class II molecules. Analysis of the TCR Vbeta element using the pol ymerase chain reaction revealed that YPM selectively activated human T cells bearing Vbeta3, Vbeta9, Vbeta13.1, and Vbeta13.2 in TCR.These r esults indicate that YPM is a potent T cell activator and has superant igenic properties (abilities to bind directly to MHC class II molecule s and selectively stimulate T cell populations bearing particular Vbet a elements in TCR). The role of YPM in the mechanism of pathogenesis o f Y. pseudotuberculosis infections manifesting acute and systemic clin ical symptoms is discussed.