Interleukin 12 Induces Leukemic T Lymphocyte Undergonig Apoptosis And Effects FasL Signal Pathway

IL-12 is a very important cytokine for the regulation of immune responses. IL-12 binds its receptor IL-12Rβ1β2 complexe distributed mainly on T and NKlymphocytes and activates intracellular JAK-STATs signal pathway and so displays marked abilities to promote the proliferation of T and NK cells, thesecretion of IFN-γ and the differentiation of ThO into Thl subpopulation. Onereason contributed to its important function in immune system is that IL-12 regulates the Fas/FasL mediated apoptosis of T lymphocytes. To study how IL-12 in high concentration regulate the expression of FasL mRNA in and the apoptosis of T cells, in this research Jurkat T lymphocytes were cultured and stimulated by IL-12, AG490 a tyrosine protein kinase ihnibitor; HA 100 a PKC ihnibitor or HA 1004 a PKA ihnibitor individually or in combination . After 6 hours or 24 hours of stimulation, Jurkat cells were stained with Annexin V and PI in combination and were analysed through flow cytometry for early apoptosis percentages. FasL mRNA expression was also detected by semi-quantatitive RT-PCR. The results as below: At 6 hours of stimulation with 50ng/rnl and 100ng/ml of IL-12 or 24 hours of stimulation with 10 ng/ml of IL-12, Jurkat cells were induced to undergo apoptosis at significantly higher percentages than the negative contral group (p<0.05). Compared with negative contral, the apoptosis percentages of IL-12 stimulating group, IL-12+AG490 group, and IL-12+HA100 group increased; Compared with IL-12 group, the apoptosis rate of IL-12+AG490 group was not significantly different, and that of the IL-12+HA100 group inreased. The FasL mRNA expression levels in IL-12 group, IL-12+AG490 group, IL-12+HA100 group and HA 100 group were higher than the contral group with significant differences(p<0.05); and those levels in AG490 group, IL-12+HA1004group and HA 1004 group were not significantly different from that of central group. From the above results we can conclude that IL-12 at high concentration can induce apoptosis of and upregulate FasL expression in Jurkat lymphocytes. These inducing effects of IL-12 are not mediated by Jak2 pathway and can be negatively regulated by PKC system.