Increased regulatory T cells in acute lymphoblastic leukemia patients

Introduction: Regulation in adaptive immune response balances a fine line that prevents instigation of self-damage or fall into unresponsiveness permitting abnormal cell growth. Mechanisms that keep this balance in check include regulatory T cells (Tregs). Tregs consist of a small but heterogeneous population which may be identified by the phenotype, CD3+CD4+CD25+CD127-. Role of Tregs in pathogenesis of cancers is thus far supported by evidence of increased Tregs in various cancers and may contribute to poorer prognosis. Tregs may also be important in acute leukemias. Objective: A review of the literature on Tregs in acute leukemias was conducted and Tregs were determined in B-cell acute lymphoblastic leukemias (ALLs). Results: Studies on Tregs in B-cell ALL are few and controversial. We observed a significantly increased percentage of Tregs (mean ± SD, 9.72 ± 3.79% vs. 7.05 ± 1.74%; P = 0.047) in the bone marrow/peripheral blood of ALL (n = 17) compared to peripheral blood of normal controls (n = 35). A positive trend between Tregs and age (R = 0.474, P = 0.055, n = 17) implicates this factor of poor prognosis in B-cell ALL. Discussion: Tregs in cancer are particularly significant in immunotherapy. The manipulation of the immune system to treat cancer has for a long time ignored regulatory mechanisms inducible or in place. In lymphoma studies tumor-specific mechanisms that are unlike conventional methods in the induction of Tregs have been hypothesized. In addition, tumor-infiltrating Tregs may present different profiles from peripheral blood pictures. Tregs will continue to be dissected to reveal their mysteries and their impact on clinical significance

Expression of killer cell immunoglobulin-like receptors (KIR) in sex-associated malignancies

Introduction: Sex shapes immune response with possible consequence on tumor immune escape. Acute lymphoblastic leukemia (ALL) predominates in males while ovarian cancer (OC) occurs in females. NK cells essential for tumor killing may have male preponderance. Association of sex, NK cell activity and malignancies is unclear. We hypothesize that sex differentially affects KIR expressions in sex-biased cancers. Method: Expression of inhibitory (KIR2DL1-5 and KIR3DL1-3) and activating (KIR2DS1-2 and 4-5 and KIR3DS1) genes in B-, T-cell ALL, OC and normal controls were determined by reverse-transcription polymerase-chain-reaction. Result: All normal males (but not females) expressed the framework genes and generally maintained haplotype A, except KIR3DL1. Normal females expressed more activating KIRs. Frequencies of KIR2DL1, 2DL4 and 2DS2 were significantly reduced among ovarian cancer patients. Sex difference in frequencies of KIR expression was not detected in ALL as majority were undetectable except framework gene KIR3DL2, was more frequent among T-ALL. Conclusion: Cancers may be associated with reduced KIR expression and influence of sex requires investigation

Association of human leukocyte antigen with precursor-B acute lymphoblastic leukaemia (pre-B ALL) in Malays

Acute Lymphoblastic Leukaemia (ALL) is one of the leukaemia subdivisions and is a malignant disorder of lymphoid progenitor cells originating from the marrow affecting both children and adults. Pathogenesis and epidemiologic studies of leukaemia in some population strongly suggest that this disease has an inherited basis and described an increase in allele frequency of HLA antigens that contribute as one of the risk factors. Thus, polymorphisms and different HLA genetic make-up in different ethnic groups make it crucial to study the disease in each population. Malays make up the largest population in Malaysia and the incidence of lymphoid leukaemia has also been reported to be highest in this group. It is hypothesised that there is an increased frequency of certain Class II (HLA-DRB1) alleles and also increase in levels of soluble HLA-DRB1 in ALL patients. The objectives of this study were to identify the HLA-DRB1 alleles associated with ALL patients of Malay ethnicity in Malaysia, and further sequence the identified risk alleles, and determine the soluble HLA levels in plasma in those patients compared to the healthy population. HLA-DNA Typing Class II was performed in pre-B ALL patients (n=42) by PCR-SSO (Polymerase chain reaction, sequence-specific oligonucleotides) and the data of HLA allele genotypes were compared with available data from healthy Malay population (n=1445). Furthermore, the plasma levels of soluble HLA class II (sHLA-DRB1) in patients (n=30) and controls (n=31) were determined by sandwich Enzyme-linked immunosorbent assay (ELISA). DNA sequencing of specific HLADRB1 alleles for the risk and associated alleles was also carried out on exon 2 by Sequence based typing (SBT) approach. Results show that there were higher allelic distribution of specific HLA-DRB1 alleles; HLA-DRB1*03 (P value=0.001, OR=2.92, 95% CI=1.47-5.80) and also –DRB1*16 (P value=0.001, OR=2.76, 95% CI=1.30-5.87) observed among Malay pre-B ALL patients. On the other hand, significant decrease in HLA-DRB1*07 (P value=0.032, OR=0.47, 95% CI=0.17- 1.28) and -DRB1*12 (P value=0.008, OR=0.59, CI=0.33-1.03) were seen in these patients, would suggest protective potential for the disease. Further analysis by SBT was able to clarify the resolution of risk alleles, which were HLA-DRB1*03:01:01 and HLA-DRB1*16:02:01, respectively. Polymorphisms were observed between DNA sequences of polymorphic exon 2 of patient and control groups for –DRB1*03 but not –DRB1*16. An increase in levels of soluble HLA-DRB1 in plasma also was detected in the ALL patients (0.260 ± 0.057 μg/mL) compared to normal individuals (0.051 ± 0.007 μg/mL) with p value of 0.001. The results obtained support the earlier hypothesis and suggest that HLA Class II antigens are the susceptible genes and also as possible biomarker for ALL. This investigation may contribute to aetiology and pathogenesis studies on ALL and identify HLA as potential genetic risk markers or as cancer biomarkers, and also as reference for future studies

Immune responses to human cytomegalovirus (HCMV) reactivation in allogeneic haematopoietic stem cell transplantation (HSCT)

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is commonly used to treat a range of haematological malignancies with Human cytomegalovirus (HCMV) reactivation as one of the major risk factors. HCMV reactivation is crucial as it can lead to HCMV disease and increase mortality. The CMV serostatus of the recipient and donor in the HSCT setting plays a role in determining the risk of the patient getting viral reactivation. Recent studies have also suggested that CMV reactivation after HSCT is associated with faster immune reconstitution and reduction of leukaemia relapse. This project studied the phenotype kinetics of immune cells including Natural Killer (NK) cells, CD4$^+$, CD8$^+$ and TCR$\gamma\delta$ T cells in HSCT patients after CMV reactivation. Also, the tetramer technique was used to study CMV specific CD8$^+$ and CD4$^+$ T cells responses reconstitution in these HSCT patients. Our data show that CMV reactivation gives significant impact on immune reconstitution of allo-HSCT by imprinting the immune cells with phenotypes specific to CMV. One major impact on NK cells seen in allo-HSCT with CMV reactivation is the huge expansion of CD56$^{dim}$CD16$^{bright}$ NKG2C$^+$ NK cells or the controversial ‘memory-like’ NK cells. The expansion of this NK population results in enhanced cytokines production after stimulation. In overall, the study of CMV reactivation in HSCT will ultimately give some insight of how to modify the clinical practice to target CMV reactivation and improve the overall clinical outcome

CMV reactivation initiates long-term expansion and differentiation of the NK cell repertoire

INTRODUCTION: NK cells play an important role in suppression of viral replication and are critical for effective control of persistent infections such as herpesviruses. Cytomegalovirus infection is associated with expansion of ‘adaptive-memory’ NK cells with a characteristic CD56dimCD16bright NKG2C+ phenotype but the mechanisms by which this population is maintained remain uncertain. METHODS: We studied NK cell reconstitution in patients undergoing haemopoietic stem cell transplantation and related this to CMV reactivation. RESULTS: NK cells expanded in the early post-transplant period but then remained stable in the absence of viral reactivation. However, CMV reactivation led to a rapid and sustained 10-fold increase in NK cell number. The proportion of NKG2C-expressing cells increases on all NK subsets although the kinetics of expansion peaked at 6 months on immature CD56bright cells whilst continuing to rise on the mature CD56dim pool. Phenotypic maturation was observed by acquisition of CD57 expression. Effective control of viral reactivation was seen when the peripheral NK cell count reached 20,000/ml. DISCUSSION: These data show that short term CMV reactivation acts to reprogramme hemopoiesis to drive a sustained modulation and expansion of the NK cell pool and reveal further insight into long term regulation of the innate immune repertoire by infectious challenge