Purification and partial characterization of a product from Yersinia pseudotuberculosis with the ability to activate human T cells

We tried to purify a substance exhibiting mitogenicity for human peripheral blood lymphocytes from Yersinia pseudotuberculosis isolated from patients with Y. pseudotuberculosis infection manifesting acute and systemic clinical symptoms. The supernatant of a suspension of the bacteria disrupted by sonication was serially chromatographed on DEAE-Sepharose fast-flow, Sephacryl S-100 HR, and TSK-gel G2000SW high-pressure liquid chromatography columns. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that the purified mitogenically active substance migrated as a single band corresponding to a molecular mass of 21 kDa. We designated the purified substance Y. pseudotuberculosis-derived mitogen (YPM). YPM stimulated human peripheral T cells to proliferate and produce interleukin-2 at 0.1 ng/ml or more. YPM-induced T-cell activation required the expression of HLA class II molecules on accessory cells.