Functional properties of human thymoma lymphocytes: role of subcellular factors in blastic activation.

The proliferative responses to phytohemagglutinin and the role of subcellular factors in the modulation of blastogenesis of thymoma lymphocytes from 5 thymoma patients were investigated. The addition of exogenous interleukin 1, a macrophage product, strongly augmented the blastic transformation of cultured thymocytes from both normal and neoplastic glands by influencing the production of interleukin 2 (IL-2) by a well-defined T-cell subset. The magnitudes of the blastic responses were ultimately modulated by the amount of IL-2 released in culture. The higher proliferative responses exhibited by thymocytes from thymoma were effectively sustained by a higher production of IL-2 in culture. In addition to having distinctive surface membrane receptors in common with normal thymocytes, thymoma lymphocytes were also under the influence of the same subcellular factors involved in T-cell blastic activation as thymocytes. These observations imply the presence of functionally distinct subpopulations in the thymoma lymphocyte component and add arguments in favor of their nonneoplastic nature.