[THE INDUCTION OF CD25 EXPRESSION IN Jurkat T CELLS]

The expression of an α-subunit of interleukin-2 receptor (IL-2Rα) was assessed by quantifying activation-induced upregulation of CD25 in IL-2-independent Jurkat leukemic cell line. It has been found that in growing Jurkat culture within 24 h, phytohemagglutinin (PHA, 5 μg/ml) or PHA in combination with 12,13-phorbol dibutirate (PDBu, 10(-8)M) increase the number of CD25+ cells to 32.3 ± 3.4% (n = 11) and 44.8 ± 8.6% (n = 6) respectively. Interleukin-2 (IL-2, 200 U/ml) alone or in combination with PDBu did not induce CD25 expression in Jurkat cells. All the tested stimulatory agencies affected neither the proliferation status no the growth of Jurkat cell cultures. In contrast to human blood T cells, WHI-P131, a selective pharmacological inhibitor of JAK/STAT signaling and CD25 expression, did not decrease the number of induced CD25+ cells in Jurkat culture. Flow cytometry analysis revealed a dose-dependent decrease in the proportion of cells in G1 phase and an increase in the proportion of cells in G2/M phase in WHI-P131-treated Jurkat cultures. It has been also found that WHI-P131 induces G2/M arrest in the absence of PHA or PDBu. We have concluded that (1) the IL-2-independent T cells of Jurkat line had not loss the mechanism for IL-2Rα expression in response to T cell receptor activation, (2) in the transformed T cells, WHI-P131 can arrest cell cycle at G2/M phase and has effects on targets other than IL-2 receptor-associated tyrosine kinase JAK3.