CD25 expression on the surface of Jurkat cells

Expression of the α-subunit of the interleukin-2 receptor (IL-2Rα) was assessed by quantifying CD25 upregulation in the Jurkat cell line (human acute T cell leukemia). It was found that phytohemagglutinin (PHA, 5 μmL) or PHA in combination with 12,13-phorbol dibutirate (PDBu, 10–8 M) increased the number of CD25-positive cells in the proliferating Jurkat culture. In 24 h, their number was 32.3 ± 3.4 (n = 11) and 44.8 ± 8.6% (n = 6), respectively. Interleukin-2 (IL-2, 200 U/mL), alone or together with PDBu, did not induce CD25 expression in Jurkat cells. The agents regulating normal T-cell proliferation did not affect Jurkat cell growth. It was found that, unlike normal human blood lymphocytes, tyrphostin WHI-P131, an inhibitor of JAK/STAT signaling from the IL-2 receptor to CD25, inhibited Jurkat cell growth and blocked the cell cycle in G2/M rather than decreasing the induced CD25+ cell number. It has been concluded that transformed IL-2-independent Jurkat T-cells do not lose the mechanism of IL-2Rα expression. WHI-P131, an inhibitor of IL-2 receptor-associated tyrosine kinase, JAK3 arrests the cell cycle at G2/M phase and has targets other than JAK3.