Immune defects in patients with chronic lymphocytic leukemia

Over the past decade, the introduction of nucleoside analogs and monoclonal antibodies into the treatment of patients with chronic lymphocytic leukemia (CLL) has resulted in higher rates and longer duration of response. This is a significant step towards achieving the ultimate goal of disease-eradication and improved survival. A continuing problem, however, is the susceptibility of these patients to infections. Profound dysregulation of the host immune system in patients with CLL and its impact on the clinical course of the disease are well established. A number of investigators have sought to identify the mechanisms underlying this innate immune dysfunction, which is further exacerbated by the actions of the potent therapeutic agents. The early recognition of infections as well as prophylactic administration of appropriate antibiotics has been the mainstay of managing infections in patients with CLL. Hopefully, increasing understanding of the molecular events underlying the neoplastic change in CLL will lead to more targeted and less immunosuppressive therapeutic modalities. Furthermore, the understanding of the mechanisms of immune dysfunction in CLL is of pivotal importance in the novel immune-based therapeutic strategies currently under development.     

T cell helper defect in patients with chronic lymphocytic leukemia.

Purified peripheral blood T lymphocytes from normal donors were shown to help allogeneic tonsillar B cells to differentiate and secrete specific anti-SRBC antibody in vitro in a plaque-forming assay. Utilizing this system, a comparison was made between the allogeneic helper activity generated by the T cells of normal individuals and patients with various disease states. Allogeneic helper activity was absent when T lymphocytes from patients with CLL were used. Conversely, relatively normal allogeneic helper function was provided by T cells of patients with a variety of other disorders studied. Thus, a functional deficiency was identified in CLL patients in the subpopulation of regulatory T cells responsible for providing helper activity in allogeneic interactions.     

Menstruation protects women from B-cell chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) affects women and men with different frequency: men show a more than double as high risk to acquire this disease than women. The reason for this sex-related difference is unknown. It is proposed here that menstruation confers advantages to women in two ways: i) early stage B-CLL cells and/or their potential precursors are partially removed from the body with menstrual bleeding which includes shedding of endometrial tissue; and ii) during degradation of the remaining endometrial tissue an immune response against B-CLL is triggered. The regular reduction of potential B-CLL cells throughout pre-menopausal life as well as the immunization against B-CLL would enable the female organism to better control outbreak and course of the disease. Both processes depend on specific binding of the leukemic cells to the endometrial tissue. CD23 expressed on the surface of B-CLL cells is suggested to mediate binding to the vitronectin receptor/CD47 expressed on endometrium. The menstrual inflammatory process includes danger signals that might facilitate initiation of an anti-leukemia immune response. Menstrual immunization might explain sex-related differences in clinical features of other malignancies as well and might therefore have broad implications for the development of individualized therapies.     

Biology of chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (CLL) lies at the cross-roads of hematology, immunology and oncology for at least three major reasons: (a) it is the prototype of human malignancies that primarily involve defects in the induction of apoptosis; (b) CLL patients develop a severe immunodeficiency with progressive hypogammaglobulinemia; and (c) they have a high prevalence of autoimmune phenomena. Recent advances in the biology of the malignant cell in CLL lead to a scenario comprised of two basic elements: first, CLL cells are optimally organized to survive in their niches because their ability to undergo apoptosis is severely hampered; second, they have a microenvironment-dependence that promotes their extended survival, a situation that arises most probably through direct cell-to-cell contacts. In addition, CLL cells themselves are the major accessory cells in CLL, but are inefficient antigen-presenting cells. This latter defect may provide a clue to reinterpret the events of immunodeficiency and autoimmunity.     

Cortisol catabolism by lymphocytes of patients with chronic lymphocytic leukemia

A low rate of catabolism of cortisol by lymphocytes correlates with high sensitivity of the cells to the steroid and causes them to die at a greater rate than control samples. Since lymphocytes of patients with chronic lymphocytic leukemia respond to treatment with glucocorticosteroids and are cortisol sensitive, we attempted to see whether their capability to catabolize cortisol differs from that of normal lymphocytes. No difference was found between the two groups of cells with regard to the pattern of cortisol metabolites. However, the lymphocytes of the chronic lymphocytic leukemia groups showed a total cortisol catabolism per cell that was significantly lower than that of the control group. Patients with low lymphocyte count in peripheral blood showed a relatively higher cortisol metabolism by lymphocytes per cell than those with high counts.     

A human alloantiserum precipitates Ia-like molecules from chronic lymphocytic leukemia cells.

Alloantigens specific for human B lymphocytes can be identified with selected antisera. These antigens have similarities to murine Ia antigens in that they are found on human B lymphocytes and are controlled by genes linked to genes controlling HLA. Chronic lymphocytic leukemia cells bearing B cell antigens were labeled with 3H leucine and the membrane components reacting with the B cell antisera isolated by immunoprecipitation. These membrane components had m.w. of 33,000 and 24,000 daltons similar to the murine Ia antigens. The results complete the homology of murine Ia and human B cell alloantigens.     

Molecular pathogenesis of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is unique among malignancies since it represents an accumulation of B-lymphocytes resistant to apoptosis. Several factors are thought to confer this unusual feature to a CLL B-cell. Misbalance between cytoplasmic pro-survival and pro-death molecules, such as Bcl-2, Mcl-1 and alike, appears to be one of the key factors defining B-cell longevity. Autocrine pathways, such as vascular endothelial growth factor-receptor pathway, also contribute to survival. The role of B-cell receptor (BCR) is less straightforward. In the last decade it became clear that CLL does not constitute a uniform disease, but, based on the prevalence of mutations in the BCR heavy chain (IgVH), can be classified into two distinct subgroups. Several molecular markers correlate with IgVH mutations. Some of them, like zeta-chain associated protein kinase, are also involved in BCR signaling and influence cell cycle. Yet the primary pathogenic event leading to increased proliferation and survival in CLL is difficult to ascertain. Molecules involved in BCR signaling pathways and cytoplasmic pro-survival players probably act in concert to confer resistance to apoptosis. In this respect, the role of the B-CLL environment, which includes nurse-like cells and T-cells, cannot be underestimated. Nurse-like cells provide stimuli necessary for perpetuation of life in CLL. On the other hand, abnormal T-cell function, whether it is excessive immunosuppression delivered by regulatory T-cells or insufficient anti-tumor immunity rendered by T-helpers, allows malignant CLL cells to go unnoticed by the cellular immune system.     

The pathogenesis of chronic lymphocytic leukemia. II]

Starting from a survey of the present knowledge of morphological, immunological and biochemical characteristics of lymphocytes degenerated in leukamic respect and their kinetics, proposals are made for the pathogenesis of chronic lymphatic leukaemia (CLL). The fact that a progressing restriction of the functional immunological variety will occur in the typical CLL is discussed. Besides normal T and B cells there are elements similar to B and T cells whose percentage of proportion changes in the course of the illness with diminution of function and increasing immunological defect.     

Polyamine metabolism in chronic lymphocytic leukemia

We have previously shown that polyamines have profound effects on lymphocyte proliferation and function. We now report that the proliferative response of cultured lymphocytes from patients with chronic lymphocytic leukemia is abrogated by the addition of diacetyldiaminohexane (HMBA), the 6-carbon analogue of diacetylputrescine. In addition, this study demonstrates the post-translational modification of proteins by polyamines in CLL-lymphocytes, a decrease in the uptake of exogenous spermidine by CLL-lymphocytes which have been exposed to HMBA, and the significant conversion of spermidine to N1-acetylspermidine in CLL-lymphocytes.     

Monoclonal antibody therapy of chronic lymphocytic leukemia

Cure of patients with chronic lymphocytic leukemia (CLL) has been an elusive goal. The recent availability of active monoclonal antibodies has rekindled enthusiasm for new and innovative therapeutic approaches. Alemtuzumab, induces responses in about a third of patients with relapsed or refractory CLL following therapy with fludarabine and an alkylating agent. Whereas, rituximab has limited activity in previously treated patients, response rates of 50-70% have been reported in those without prior therapy. Recent data on combinations with rituximab and chemotherapy have shown promise for improving patient outcome. Newer antibodies in development include the primatized monoclonal antibody lumiliximab (IDEC-152), directed against CD23. Other biological approaches include the use of antisense oligonucleotides, proapoptic small molecules, and vaccines directed against the malignant B cells. The rational development of combinations of these promising approaches may eliminate the need for chemotherapy, leading to safer and more effective approaches for patients with CLL.     

Genetic features of B-cell chronic lymphocytic leukemia

The genetic features of B-cell chronic lymphocytic leukemia (CLL) are currently being reassessed by molecular cytogenetic techniques such as fluorescence in situ hybridization (FISH). Conventional cytogenetic studies by chromosome banding are difficult in CLL mainly because of the low in vitro mitotic activity of the tumor cells, which leads to poor quantity and quality of metaphase spreads. Molecular genetic analyses are limited because candidate genes are known for only a few chromosomal aberrations that are observed in CLL. FISH was found to be a powerful tool for the genetic analysis of CLL as it overcomes both the low mitotic activity of the CLL cells and the lack of suitable candidate genes for analysis. Using FISH, the detection of chromosomal aberrations can be performed at the single cell level in both dividing and non-dividing cells, thus circumventing the need of metaphase preparations from tumor cells. Probes for the detection of trisomies, deletions and translocation breakpoints can be applied to the regions of interest with the growing number of clones available from genome-wide libraries. Using the interphase cytogenetic FISH approach with a disease specific set of probes, chromosome aberrations can be found in more than 80% of CLL cases. The most frequently observed abnormalities are losses of chromosomal material, with deletions in band 13q14 being the most common, followed by deletions in 11q22-q23, deletions in 17p13 and deletions in 6q21. The most common gains of chromosomal material are trisomies 12q, 8q and 3q. Translocation breakpoints, in particular involving the immunoglobulin heavy chain locus at 14q32, which are frequently observed in other types of non-Hodgkin's lymphoma, are rare events in CLL. Genes affected by common chromosome aberrations in CLL appear to be p53 in cases with 17p deletion and ataxia telangiectasia mutated (ATM), which is mutated in a subset of cases with 11q22-q23 aberrations. However, for the other frequently affected genomic regions, the search for candidate genes is ongoing. In parallel, the accurate evaluation of the incidence of chromosome aberrations in CLL by FISH allows the correlation of genetic abnormalities with clinical disease manifestations and outcome. In particular, 17p abnormalities and deletions in 11q22-q23 have already been shown to be among the most important independent prognostic factors identifying subgroups of patients with rapid disease progression and short survival. In addition, deletion 17p has been associated with resistance to treatment with purine analogs. Therefore, genetic abnormalities may allow a risk assessment for individual patients at the time of diagnosis, thus giving the opportunity for a risk-adapted management.     

Dendritic cells from chronic lymphocytic leukemia patients are normal regardless of Ig V gene mutation status

Patients with B-type chronic lymphocytic leukemia (B-CLL) segregate into 2 subgroups based on the mutational status of the immunoglobulin (Ig) V genes and the patients in these subgroups follow very different clinical courses. To examine whether dendritic cells (DCs) generated from CLL patients can be candidates for immune therapy, we compared the phenotypic and functional capacities of DCs generated from patients of the 2 CLL subgroups (normal age-matched subjects [normal-DCs]). Our data show that immature DCs from B-CLL patients (B-CLL-DCs) have the same capacity to take up antigen as those from normal controls. Furthermore, B-CLL-DCs generated from the 2 CLL subgroups up-regulated MHC-II, CD80, CD86, CD83, CD40, and CD54 and down-regulated CD206 in response to stimulation with a cocktail of cytokines (CyC) and secreted increased levels of tumor necrosis factor alpha, interleukin (IL)-8, IL-6, IL-12 (p70), and RANTES in a manner typical of mature normal-DCs. Interestingly, CD54 was significantly more up-regulated by CyC in B-CLL-DCs compared with normal-DCs. Except for CD54, no significant differences in surface molecule expression were observed between normal-DCs and B-CLL-DCs. B-CLL-DCs from both subgroups, including 6 patients with VH1-69, that usually fare poorly, presented tetanus toxoid to autologous T cells in vitro similar to normal- DCs. Our data show that DCs generated from the B-CLL subgroup with unmutated Ig V genes are functionally normal. These results are very promising for the use of DCs from patients with poor prognosis for immunotherapy.     

Galactose-1-phosphate uridylyltransferase activity in chronic lymphocytic leukemia.

Galactose-1-phosphate uridylytransferase (E.C.2.7.12) activity was measured in both lymphoid and erythroid cells from patients with chronic lymphocytic leukemia (CLL). Decreased enzyme activity was found in both cell types using two assay methods. The results suggest the presence of an inhibitor of the enzyme in CLL patients. A correlation between decreased uridyl transferase activity and glycogen accumulation in CLL is postulated.     

Lymphocyte cholesterol synthesis in chronic lymphocytic leukemia

Studies in B and T lymphocytes from two patients with B cell chronic lymphocytic leukemia (CLL) showed that the rate of cholesterol synthesis and hydroxymethylglutaryl (HMG)-CoA reductase activity in the malignant cell--the B lymphocyte--did not differ from that in normals, before or after the treatment. Cholesterol synthesis and HMG-CoA reductase activity in T cells, on the other hand, from one patient (H.E.) before therapy, were only one-fifth of that in normals and in the other patient (J.R.) receiving treatment. Following chemotherapy and treatment with prednisone, T lymphocytes from H.E. exhibited normal cholesterol metabolism.     

B-lymphocyte colony formation in chronic lymphocytic leukemia

A semisolid culture system for B-cell colony formation is described. The system includes pretreatment of B-cells by neuraminidase-galactose oxidase and help of mitomycin-treated T-cells. With this assay system, colony-forming B-cell precursors were detected in all eight patients we studied with B-cell chronic lymphocytic leukemia. These patients' own T-cell helper effect was less than that of normal T-cells.     

Genetic alteration associated with chronic lymphocytic leukemia

The genetics of B-cell chronic lymphocytic leukemia (B-CLL) differ considerably from most other forms of hematologic malignancy which are usually characterized by chromosome translocations. B-CLL typically contains chromosomal deletions and chromosomes 13q14 and 11q22-->q23 are the most common. These two regions appear to share a common ancestral origin (Auer et al., 2007b). Overall, chromosomal abnormalities can be found in the majority of patients with B-CLL when using sensitive techniques (Dohneret al., 2000) and possibly reflects an underlying predisposition, with a small but significant number of familial cases. Although single and consistent abnormalities are most common, multiple rearrangements can occur, often with disease progression (Feganetal., 1995; Dohner et al., 2000). Regions of recurrent deletion suggest the presence of tumor suppressor genes if following Knudson's theoretical 2-hit model. However, despite extensive sequencing analysis over the last decade and lack of pathogenic mutations identified, there has been a move away from this suggested hypothesis and alternative mechanisms of gene inactivation involving epigenetic silencing or haploinsufficiency may be considered as more likely in this disease. This review focuses on the common genetic abnormalities in B-CLL and relates them to some of the more recent hypotheses on inactivation of genes within these regions of deletion.