Inhibition of interleukin-2 receptor (CD25) expression induced on T cells from children with acute lymphoblastic leukemia

Exonal switch down-regulates the expression of CD5 on blasts of acute T cell leukaemia

To date, CD5 expression and its role in acute T cell lymphoblastic leukaemia (T-ALL) have not been studied closely. We observed a significant reduction in surface expression of CD5 (sCD5) on leukaemic T cells compared to autologous non-leukaemic T cells. In this study, we have shown the molecular mechanism regulating the expression and function of CD5 on leukaemic T cells. A total of 250 patients suffering from leukaemia and lymphoma were immunophenotyped. Final diagnosis was based on their clinical presentation, morphological data and flow cytometry-based immunophenotyping. Thirty-nine patients were found to be of ALL-T origin. Amplification of early region of E1A and E1B transcripts of CD5 was correlated with the levels of surface and intracellular expression of CD5 protein. Functional studies were performed to show the effect of CD5 blocking on interleukin IL-2 production and survival of leukaemic and non-leukaemic cells. Lack of expression of sCD5 on T-ALL blasts was correlated closely with predominant transcription of exon E1B and significant loss of exon E1A of the CD5 gene, which is associated with surface expression of CD5 on lymphocytes. High expression of E1B also correlates with increased expression of cytoplasmic CD5 (cCD5) among leukaemic T cells. Interestingly, we observed a significant increase in the production of IL-2 by non-leukaemic T cells upon CD5 blocking, leading possibly to their increased survival at 48 h. Our study provides understanding of the regulation of CD5 expression on leukaemic T cells, and may help in understanding the molecular mechanism of CD5 down-regulation.

Increased Th22 cells as well as Th17 cells in patients with adult T-cell acute lymphoblastic leukemia

BACKGROUND

Immune regulation is important for the pathogenesis of T-cell acute lymphoblastic leukemia (T-ALL). Th22 cells are recently-identified CD4(+) T cells that implicated in the pathogenesis of many hematological diseases, such as AML. However, the role of Th22 cells in the pathophysiology of T-ALL remains unclear. We examined the Th22, Th17 and Th1 cell frequencies in peripheral blood of T-ALL patients.

METHODS

We studied 24 newly-diagnosed (ND), 17 morphologic complete remission (CR) T-ALL patients and 30 healthy controls. Th subsets were examined by flow cytometry. Plasma IL-22 and IL-17 concentrations were measured by ELISA. Transcription factor RORC, T-bet and AHR mRNA expressions were examined by RT-PCR.

RESULTS

Th22, Th17 frequencies, plasma IL-22 concentration and AHR expression were significantly increased in ND or CR T-ALL patients compared with controls. Moreover, Th22 showed positive correlation with Th17 or Th1 cells in T-ALL patients. However, a significant decrease of IL-17 concentration, Th1 frequency and T-bet expression was found in ND or CR ALL patients compared with controls. Furthermore, Th17 cells showed positive correlation but Th1 cells showed negative correlation with white blood cell counts.

CONCLUSION

The profile of Th subsets was distinct for T-ALL patients and showed some correlations with clinical index, which suggest that these Th subsets may be implicated in the pathogenesis of T-ALL and be reasonable targets for therapeutic intervention.

Changes in acetylcholinesterase (AchE) activity in lymphocytes and whole blood in acute lymphoblastic leukemia patients

BACKGROUND

Acute lymphoblastic leukemia (ALL) is a type of cancer that affects lymphocytes and it is the most common form of cancer in children. Acetylcholinesterase (AChE) is well known as having non-cholinergic functions and has been detected in the blood and plasma of humans including in lymphocytes. Thus, we investigated whole blood and lymphocyte AChE activity in patients with ALL.

METHODS

This study was performed on 72 children with ALL divided into 4 groups: newly diagnosed, remission induction, remission maintenance and out-of-treatment and one control group of 50 healthy subjects. We determined AChE activity in whole blood and lymphocytes of these patients.

RESULTS

Results demonstrated that whole blood AChE activity was enhanced in the newly diagnosed group and reduced in the remission induction and remission maintenance groups in relation to the control group. For lymphocyte AChE activity we found an increase in the newly diagnosed group and a decrease in the remission induction group in relation to the control.

CONCLUSIONS

These results suggest that AChE activity was altered in ALL patients. This fact may be related with the essential role played by AChE in the development of hematological disease and its contribution to the regulation of immune function.

CD30L up-regulates CD30 and IL-4 expression by T cells

CD30L is frequently expressed on acute myeloid leukemia (AML) blasts. Its presence is associated with the co-expression of interleukin-4 (IL-4) receptor and with the expansion of specific T-helper 2 (Th2) cell subsets producing IL-4 and expressing CD30. Recombinant CD30L-bearing cells up-regulated the expression of surface CD30 and increased the production of IL-4 and soluble (s) CD30 by co-cultured T cells. These findings were confirmed with AML blasts expressing surface CD30L, where blocking anti-CD30 antibodies completely abolished the release of sCD30 and reduced the production of IL-4. Our data indicates a direct role of CD30L(+) neoplastic cells in driving the immune response toward a Th2-polarized non-protective state.

Analysis of T-cell defects in the specific immune response against acute lymphoblastic leukemia cells

We previously showed that a specific antileukemia T-cytotoxic response is spontaneously elicited in acute lymphoblastic leukemia (ALL) patients and might contribute to host antileukemia defense, even though it is insufficient for tumor growth control. In this study, we report that multifactorial factors account for some of the acquired immune defects seen in ALL patients. In bone marrow of ALL patients, T cells do not express CD40L and CD25 markers, their apoptosis rate is increased, and a predominance of a CD4 cell subset expressing a Th2 phenotype is detected. A lack of expression of B7-1 molecules and other activation molecules is observed on all ALL blasts. These different parameters combined lead to in vivo dysfunction of T-cell proliferative and cytotoxic activity.

CD3-mediated T cell activation is inhibited by anti-CD44 monoclonal antibodies directed to the hyaluronan-binding region

The CD44 molecule has been shown to play a role in T cell adhesion and activation. We have investigated the ability of five anti-CD44 monoclonal antibodies (MoAb) including 15C6, 18A3, BU75 (Ancell), J173 (Immunotech), and L178 (Becton Dickinson) to regulate T cell activation. Three MoAb: 15C6, BU75, and J173 were found to selectively inhibit DNA synthesis, interleukin-2 (IL-2) receptor expression, and G1-->S transition of the cell cycle in T cells stimulated with anti-CD3 MoAb. None of anti-CD44 MoAb had influence on T cell proliferation induced by IL-2 or phorbol 12-myristate 13-acetate plus ionomycin. Inhibition of the CD3 pathway by anti-CD44 MoAb occurred by binding of MoAb directly to T cells without the involvement of monocytes or Fc receptors. In addition, the inhibitory anti-CD44 MoAb clearly suppressed intracellular calcium mobilization in T cells stimulated with anti-CD3 MoAb. Interestingly, the ability of anti-CD44 MoAb to inhibit T cell activation was well correlated with their capability to block the binding of hyaluronan (HA) to CD44 molecules. These results suggest that anti-CD44 MoAb directed to HA-binding site could selectively inhibit CD3-mediated T cell activation. Furthermore, CD44-mediated inhibitory signals would be linked to the blocking of early CD3-mediated signal transduction.