Functional characterization of NK cells in Mexican pediatric patients with acute lymphoblastic leukemia: Report from the Mexican Interinstitutional Group for the Identification of the Causes of Childhood Leukemia

Acute lymphoblastic leukemia (ALL) is the most common cancer in children around the globe. Mexico City has one of the highest incidence rates of childhood leukemia worldwide with 49.5 cases per million children under the age of 15 which is similar to that reported for Hispanic populations living in the United States. In addition, it has been noted a dismal prognosis in Mexican and Hispanic ALL pediatric population. Although ALL, like cancer in general, has its origins in endogenous, exogenous, and genetic factors, several studies have shown that the immune system also plays a deterministic role in cancer development. Among various elements of the immune system, T lymphocytes and NK cells seem to dominate the immune response against leukemia. The aim of the present study was to perform a phenotypic and functional characterization of NK cells in ALL Mexican children at the moment of diagnosis and before treatment initiation. A case-control study was conducted by the Mexican Interinstitutional Group for the Identification of the Causes of Childhood Leukemia (MIGICCL). 41 cases were incident ALL children younger than 17 years old and residents of Mexico City. 14 controls were children without leukemia, matched by age and sex with cases. NK cell function was evaluated by degranulation assays towards K562 cells and SLAM-associated protein (SAP) expression was measured by intracellular staining. All assays were performed using peripheral blood mononuclear cells from controls and patients. The results indicate that NK mediated cytotoxicity, measured by CD107a degranulation assays in response to K562 cells, was reduced in ALL patients compared to controls. Interestingly, an impaired NK cell killing of target cells was not equally distributed among ALL patients. In contrast to patients classified as high-risk, standard-risk patients did not display a significant reduction in NK cell-mediated cytotoxicity. Moreover, patients presenting a leukocyte count ≥ 50,000xmm³ displayed a reduction in NK-cell mediated cytotoxicity and a reduction in SAP expression, indicating a positive correlation between a reduced SAP expression and an impaired NK cell-mediated citotoxicity. In the present study it was observed that unlike patients with standard-risk, NK cells from children presenting high-risk ALL, harbor an impaired cytotoxicity towards K562 at diagnosis. In addition, NK cell function was observed to be compromised in patients with a leukocyte count ≥50,000xmm³, where also it was noticed a decreased expression of SAP compared to patients with a leukocyte count <50,000xmm³. These data indicate NK cell-mediated cytotoxicity is not equally affected in ALL patients, nevertheless a positive correlation between low SAP expression and decreased NK cell-mediated cytotoxicity was observed in ALL patients with a leukocyte count ≥50,000xmm³. Finally, an abnormal NK cell-mediated cytotoxicity may represent a prognostic factor for high-risk acute lymphoblastic leukemia.

Effect of low-dose cyclosporine A in the treatment of refractory proteinuria in childhood-onset lupus nephritis

We performed a prospective study to evaluate the efficacy and safety of low-dose cyclosporine A (CSA) treatment in paediatric lupus nephritis refractory to conventional therapy. Seven children with biopsy-proven Class III-IV lupus nephritis were treated with CSA (2-4 mg/kg/day) combined with low-dose prednisone for one year. All patients had failed to achieve sustained proteinuria remission with corticosteroids and cytotoxic drugs. Proteinuria decreased from median value of 2.5 g/24 hours (range, 1.2-4.9) to 0.14 g/24 hours (range, 0.0-0.84) after treatment (P = 0.018). Median values of creatinine clearance and serum creatinine did not change significantly. Median systemic lupus erythematosus disease activity index score decreased from 12 (range, 6-16) to 4 (range, 0-8) at end of treatment (P = 0.027). However, two patients experienced flares of extrarrenal manifestations and complement levels did not improve. Moreover, most patients relapsed with proteinuria within a few months of stopping CSA therapy. Side effects were not significant. In conclusion, low-dose of CSA combined with steroids appears to be useful to reduce proteinuria in paediatric proliferative lupus nephritis refractory to steroids and cytotoxic drugs; however, relapses are common after CSA discontinuation. Further studies are needed to define the precise role of CSA in paediatric lupus nephritis.