Suppression of human lymphocyte proliferation and cytotoxic T lymphocyte generation by a soluble factor derived from K562 cells
The human myeloid leukemia cell line, K562, secrets a lymphocyte growth-suppressive factor (LGSF). We report our investigation of the immunological and chemical features of this factor. LGSF showed no cytolytic effect on human peripheral blood mononuclear cells (PBMC). Nevertheless, LGSF adequately suppressed in vitro alloantigen- or mitogen (PHA, ConA, PWM)-stimu-lated human PBMC proliferation and alloantigen-in-duced cytotoxic T lymphocyte generation, in antigen-nonspecific and LGSF concentration-related manners. LGSF retained activity after filtration through a 0.22 |im filter membrane and storage at — 80 °C for 6 months. Ultrafiltration experiments indicated that suppressive activity was retained in the higher molecular weight fraction (MW > 100000) and that the activity was heat-labile at 56 °C for 30 min. These results strongly suggested that LGSF is a noncytotoxically immunosuppressive substance with a high molecular weight.
Key wordsImmunosuppression Cytokine Human leukemia cell line Lymphocyte growth suppressive factor Cytotoxic Tlymphocyte
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