CD1d expression is higher in chronic lymphocytic leukemia patients with unfavorable prognosis

Through the analysis of CD1d expression by flow cytometry and qRT-PCR we showed lower CD1d molecule and CD1d mRNA expression in B cells of CLL patients than of healthy controls. The frequency of CD1d(+)/CD19(+) cells, CD1d staining intensity and CD1d transcript levels increased with the disease stage. CD1d expression was positively associated with ZAP-70 and CD38 expressions as well as with unfavourable cytogenetic changes. We established the relationship between high CD1d expression and shorter time to treatment and overall survival. We observed that CD1d expression in individual patients significantly changed over time. The percentage of CD1d(+)/CD19(+) cells inversely correlated with the percentage of iNKT cells.

Autophagy maturation associated with CD38-mediated regulation of lysosome function in mouse glomerular podocytes

Podocytes are highly differentiated glomerular epithelial cells that contribute to the glomerular barrier function of kidney. A role for autophagy has been proposed in maintenance of their cellular integrity, but the mechanisms controlling autophagy in podocytes are not clear. The present study tested whether CD38-mediated regulation of lysosome function contributes to autophagic flux or autophagy maturation in podocytes. Podocytes were found to exhibit a high constitutive level of LC3-II, a robust marker of autophagosomes (APs), suggesting a high basal level of autophagic activity. Treatment with the mTOR inhibitor, rapamycin, increased LC3-II and the content of both APs detected by Cyto-ID Green staining and autophagolysosomes (APLs) measured by acridine orange staining and colocalization of LC3 and Lamp1. Lysosome function inhibitor bafilomycin A1 increased APs, but decreased APLs content under both basal and rapamycin-induced conditions. Inhibition of CD38 activity by nicotinamide or silencing of CD38 gene produced the similar effects to that bafilomycin A1 did in podocytes. To explore the possibility that CD38 may control podocyte autophagy through its regulation of lysosome function, the fusion of APs with lysosomes in living podocytes was observed by co-transfection of GFP-LC3B and RFP-Lamp1 expression vectors. A colocalization of GFP-LC3B and RFP-Lamp1 upon stimulation of rapamycin became obvious in transfected podocytes, which could be substantially blocked by nicotinamide, CD38 shRNA, and bafilomycin. Moreover, blockade of the CD38-mediated regulation by PPADS completely abolished rapamycin-induced fusion of APs with lysosomes. These results indicate that CD38 importantly control lysosomal function and influence autophagy at the maturation step in podocytes.

Large changes in NAD levels associated with CD38 expression during HL-60 cell differentiation

NAD is an important cofactor involved in multiple metabolic reactions and as a substrate for several NAD-dependent signalling enzymes. One such enzyme is CD38 which, alongside synthesising Ca(2+)-releasing second messengers and acting as a cell surface receptor, has also been suggested to play a key role in NAD(+) homeostasis. CD38 is well known as a negative prognostic marker in B-CLL but the role of its enzymatic activity has not been studied in depth to date. We have exploited the HL-60 cell line as a model of inducible CD38 expression, to investigate CD38-mediated regulation intracellular NAD(+) levels and the consequences of changes in NAD(+) levels on cell physiology. Intracellular NAD(+) levels fell with increasing CD38 expression and this was reversed with the CD38 inhibitor, kuromanin confirming the key role of CD38 in NAD(+) homeostasis. We also measured the consequences of CD38 expression during the differentiation on a number of functions linked to NAD(+) and we show that some but not all NAD(+)-dependent processes are significantly affected by the lowered NAD(+) levels. These data suggest that both functional roles of CD38 might be important in the pathogenesis of B-CLL.

Residual immune dysregulation syndrome in treated HIV infection

Antiretroviral therapy has revolutionized the course of HIV infection, improving immune function and decreasing dramatically the mortality and morbidity due to the opportunistic complications of the disease. Nonetheless, even with sustained suppression of HIV replication, many HIV-infected persons experience a syndrome characterized by increased T cell activation and evidence of heightened inflammation and coagulation. This residual immune dysregulation syndrome or RIDS is more common in persons who fail to increase circulating CD4+ T cells to normal levels and in several epidemiologic studies it has been associated with increased morbidity and mortality. These morbid and fatal events are not the typical opportunistic infections and malignancies seen in the early AIDS era but rather comprise a spectrum of cardiovascular events, liver disease, metabolic disorders, kidney disease, bone disease, and a spectrum of malignant complications distinguishable from the opportunistic malignancies that characterized the earlier days of the AIDS epidemic. While immune activation, inflammation, and coagulopathy are characteristic of untreated HIV infection and improve with drug-induced control of HIV replication, the drivers of RIDS in treated HIV infection are incompletely understood. And while inflammation, immune activation, and coagulopathy are more common in treated persons who fail to restore circulating CD4+ T cells, it is not entirely clear how these two phenomena are linked.

ZAP70 in B-CLL cells related to the expression in NK cells is a surrogate marker for mutational status

The strongest prognostic factor in chronic B-cell lymphocytic leukemia (CLL) is the mutational status of the immunoglobulin heavy chain variable region (IGHV) genes. Determination of this mutational status is laborious and therefore not applied in routine diagnostics. A search for "surrogate markers" has been conducted over the past few years. One of the most promising surrogate markers is ZAP70, but standardization of the measurement of ZAP70 has proven to be difficult. Conventionally, ZAP70 expression in CLL cells is related to ZAP70 expression in T cells. We propose a new method in which ZAP70 expression in NK cells is used as reference (new NK-MFI method). We have measured ZAP70 expression in samples of 45 previously untreated CLL patients. ZAP70 in CLL cells related to ZAP70 in NK cells correlated better to cytogenetic risk profile and mutational status than the conventional methods. Negativity of both ZAP70 (new NK-MFI method) and CD38 resulted in a probability of 90% for mutated IGHV genes. In conclusion, ZAP70 expression in CLL cells related to ZAP70 expression in NK cells is a better surrogate marker for mutational status than the conventional T cell related methods.

ZAP70 in B-CLL cells related to the expression in NK cells is a surrogate marker for mutational status

The strongest prognostic factor in chronic B-cell lymphocytic leukaemia (CLL) is the mutational status of the immunoglobulin heavy chain variable region (IGHV) genes. Determination of this mutational status is laborious and therefore not applied in routine diagnostics. A search for 'surrogate markers' has been conducted over the past few years. One of the most promising surrogate markers is ZAP70, but standardisation of the measurement of ZAP70 has proven to be difficult. Conventionally, ZAP70 expression in CLL cells is related to ZAP70 expression in T cells. We propose a new method in which ZAP70 expression in NK cells is used as reference (new NK-MFI method). We have measured ZAP70 expression in samples of 45 previously untreated CLL patients. ZAP70 in CLL cells related to ZAP70 in NK cells correlated better to cytogenetic risk profile and mutational status than the conventional methods. Negativity of both ZAP70 (new NK-MFI method) and CD38 resulted in a probability of 90% for mutated IGHV genes. In conclusion, ZAP70 expression in CLL cells related to ZAP70 expression in NK cells is a better surrogate marker for mutational status than the conventional T cell related methods. © 2013 Clinical Cytometry Society.

A CD38/CD203a/CD73 ectoenzymatic pathway independent of CD39 drives a novel adenosinergic loop in human T lymphocytes

The tumor microenvironment is characterized by of high levels of extracellular nucleotides that are metabolized through the dynamic and sequential action of cell surface enzymes (ectoenzymes). These ectoenzymes operate according to their spatial arrangement, as part of (1) continuous (molecules on the same cell) or (2) discontinuous (molecules on different cells) pathways, the latter being facilitated by restricted cellular microenvironment. The outcome of this catabolic activity is an increase in the local concentration of adenosine, a nucleoside involved in the control of inflammation and immune responses. The aim of the work presented here was to demonstrate that a previously unexplored enzymatic pathway may be an alternate route to produce extracellular adenosine. Our data show that this new axis is driven by the nucleotide-metabolizing ectoenzymes CD38 (an NAD⁺ nucleosidase), the ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1, also known as CD203a or PC-1) and the 5′ ectonucleotidase (5′-NT) CD73, while bypassing the canonical catabolic pathway mediated by the nucleoside tri- and diphosphohydrolase (NTPDase) CD39. To determine the relative contributions of these cell surface enzymes to the production of adenosine, we exploited a human T-cell model allowing for the modular expression of the individual components of this alternative pathway upon activation and transfection. The biochemical analysis of the products of these ectoenzymes by high-performance liquid chromatography (HPLC) fully substantiated our working hypothesis. This newly characterized pathway may facilitate the emergence of an adaptive immune response in selected cellular contexts. Considering the role for extracellular adenosine in the regulation of inflammation and immunogenicity, this pathway could constitute a novel strategy of tumor evasion, implying that these enzymes may represent ideal targets for antibody-mediated therapy.

Schistosoma mansoni NAD(+) catabolizing enzyme: identification of key residues in catalysis

Schistosoma mansoni NAD(+) catabolizing enzyme (SmNACE), a distant homolog of mammalian CD38, shows significant structural and functional analogy to the members of the CD38/ADP-ribosyl cyclase family. The hallmark of SmNACE is the lack of ADP-ribosyl cyclase activity that might be ascribed to subtle changes in its active site. To better characterize the residues of the active site we determined the kinetic parameters of nine mutants encompassing three acidic residues: (i) the putative catalytic residue Glu202 and (ii) two acidic residues within the 'signature' region (the conserved Glu124 and the downstream Asp133), (iii) Ser169, a strictly conserved polar residue and (iv) two aromatic residues (His103 and Trp165). We established the very important role of Glu202 and of the hydrophobic domains overwhelmingly in the efficiency of the nicotinamide-ribosyl bond cleavage step. We also demonstrated that in sharp contrast with mammalian CD38, the 'signature' Glu124 is as critical as Glu202 for catalysis by the parasite enzyme. The different environments of the two Glu residues in the crystal structure of CD38 and in the homology model of SmNACE could explain such functional discrepancies. Mutagenesis data and 3D structures also indicated the importance of aromatic residues, especially His103, in the stabilization of the reaction intermediate as well as in the selection of its conformation suitable for cyclization to cyclic ADP-ribose. Finally, we showed that inhibition of SmNACE by the natural product cyanidin requires the integrity of Glu202 and Glu124, but not of His103 and Trp165, hence suggesting different recognition modes for substrate and inhibitor.

Computational analysis optimizes the flow cytometric evaluation for lymphoma

BACKGROUND

Although many clinical laboratories are adopting higher color flow cytometric assays, the approach to optimizing panel design and data analysis is often traditional and subjective. In order to address the question "What is the best flow cytometric strategy to reliably distinguish germinal center B-cell lymphoma (GC-L) from germinal center hyperplasia (GC-H)?" we applied a computational tool that identifies target populations correlated with a desired outcome, in this case diagnosis.

DESIGN

Cases of GC-H and GC-L evaluated by flow cytometric immunophenotyping using CD45, CD20, kappa, lambda, CD19, CD5, CD10, CD38, were analyzed with flowType and RchyOptimyx to construct cellular hierarchies that best distinguished the two diagnostic groups.

RESULTS

The population CD5-CD19+CD10+CD38- had the highest predictive power. Manual reanalysis confirmed significantly higher CD10+/CD38-B-cells in GC-L (median 12.44%, range 0.74-63.29, n = 52) than GC-H (median 0.24%, 0.03-4.49, n = 48, P = 0.0001), but was not entirely specific. Difficulties encountered using this computational approach included the presence of CD10+ granulocytes, continuously variable B-cell expression of CD38, more variable intensity antigen staining in GC-L and inability to assess the contribution of light chain restriction.

CONCLUSION

Computational analysis with construction of cellular hierarchies related to diagnosis helped guide manual analysis of high dimensional flow cytometric data. This approach highlighted the diagnostic utility of CD38 expression in the evaluation of B-cells with a CD10+ GC phenotype. In contrast to computational analysis of non-neoplastic cell populations, evaluation of neoplastic cells must be able to take into consideration increased variability in antigen expression.

Morphology and expression status investigations of specific surface markers on B-cell chronic lymphocytic leukemia cells

The morphology of cells and expression status of specific surface markers [cluster of differentiation (CD)], such as CD5, CD19, CD20, CD38, and CD45, have long been considered as the essential indicators for the diagnosis and prognosis of B-cell chronic lymphocytic leukemia (B-CLL). Clinically, it is difficult to simultaneously obtain cell morphology and distribution of surface markers with flow cytometry, especially for some surrogate markers such as CD38. Here, as an alternative and complementary prognostic method, fluorescence microscopy and image processing method are introduced to directly visualize the cells from patients and to quantitatively determine the expression status of surface markers. In this study, the morphological parameters of B-CLL cells were measured to establish the correlation between the cellular morphology and the surface marker expression. It was clear that the CD38+ and CD38- B-CLL cells from the same CD38+ patients had hardly any size differences; however, an increase in perimeter was observed for CD38- patients. Moreover, the expression level of the receptors on the cell was independent of the cell size. There was no evidence showing that the expression intensities of CD19 and CD38 were related to each other for the CD38+ B-CLL cells. On the same cells, CD5 was more selectively expressed on the cell membrane; however, the expression patterns suggested that the cell membrane of CD38- B-CLL cells contained the least expression level of CD19.

Cluster of differentiation 38 (CD38) mediates bile acid-induced acinar cell injury and pancreatitis through cyclic ADP-ribose and intracellular calcium release

Aberrant Ca(2+) signals within pancreatic acinar cells are an early and critical feature in acute pancreatitis, yet it is unclear how these signals are generated. An important mediator of the aberrant Ca(2+) signals due to bile acid exposure is the intracellular Ca(2+) channel ryanodine receptor. One putative activator of the ryanodine receptor is the nucleotide second messenger cyclic ADP-ribose (cADPR), which is generated by an ectoenzyme ADP-ribosyl cyclase, CD38. In this study, we examined the role of CD38 and cADPR in acinar cell Ca(2+) signals and acinar injury due to bile acids using pharmacologic inhibitors of CD38 and cADPR as well as mice deficient in Cd38 (Cd38(-/-)). Cytosolic Ca(2+) signals were imaged using live time-lapse confocal microscopy in freshly isolated mouse acinar cells during perifusion with the bile acid taurolithocholic acid 3-sulfate (TLCS; 500 μM). To focus on intracellular Ca(2+) release and to specifically exclude Ca(2+) influx, cells were perifused in Ca(2+)-free medium. Cell injury was assessed by lactate dehydrogenase leakage and propidium iodide uptake. Pretreatment with either nicotinamide (20 mM) or the cADPR antagonist 8-Br-cADPR (30 μM) abrogated TLCS-induced Ca(2+) signals and cell injury. TLCS-induced Ca(2+) release and cell injury were reduced by 30 and 95%, respectively, in Cd38-deficient acinar cells compared with wild-type cells (p < 0.05). Cd38-deficient mice were protected against a model of bile acid infusion pancreatitis. In summary, these data indicate that CD38-cADPR mediates bile acid-induced pancreatitis and acinar cell injury through aberrant intracellular Ca(2+) signaling.

Computational analysis optimizes the flow cytometric evaluation for lymphoma

Background: Although many clinical laboratories are adopting higher color flow cytometric assays, the approach to optimizing panel design and data analysis is often traditional and subjective. In order to address the question "What is the best flow cytometric strategy to reliably distinguish germinal center B-cell lymphoma (GC-L) from lymphoid hyperplasia (GC-H)?" we applied a computational tool that identifies target populations correlated with a desired outcome, in this case diagnosis. Design: Cases of GC-H and GC-L with a germinal center phenotype, evaluated by flow cytometric immunophenotyping using CD45, CD20, kappa, lambda, CD19, CD5, CD10, CD38, were analyzed with flowType and RchyOptimyx to construct cellular hierarchies that best distinguished the two diagnostic groups. Results: The population CD5-CD19+CD10+CD38- had the highest predictive power. Manual reanalysis confirmed significantly higher CD10+/CD38-B-cells in GC-L (median 12.44%, range 0.74 - 63.29, n=52) than GC-H (median 0.24%, 0.03 - 4.49, n=48, p=0.0001), but was not entirely specific. Difficulties encountered using this computational approach included the presence of CD10+ granulocytes, continuously variable B-cell expression of CD38, more variable intensity antigen staining in GC-L and inability to assess the contribution of light chain restriction. Conclusion: Computational analysis with construction of cellular hierarchies related to diagnosis helped guide manual analysis of high dimensional flow cytometric data. This approach highlighted the diagnostic utility of CD38 expression in the evaluation of B-cells with a CD10+ GC phenotype. In contrast to computational analysis of non-neoplastic cell populations, evaluation of neoplastic cells must be able to take into consideration increased variability in antigen expression. © 2013 Clinical Cytometry Society.

Pathology consultation on evaluating prognosis in incidental monoclonal lymphocytosis and chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a monoclonal B-cell lymphoproliferative disorder generally characterized by an indolent clinical course. However, some patients with CLL will have more aggressive disease progression, and identifying that subgroup may be important for early, or perhaps more aggressive, intervention. In addition, monoclonal B-cell lymphocytosis is often found on routine laboratory evaluation, and it is important to distinguish this entity from overt CLL. Moreover, since many patients with CLL are discovered incidentally and before significant disease progression, prognostic laboratory evaluation may become increasingly efficacious as therapeutic options replace the older strategy of expectant observation. Prognostication may be especially critical if it correctly identifies patients with early stage CLL who are at high risk of clonal evolution and/ or resistance to chemoimmunotherapy. Laboratory studies include surface CD38 and intracellular ZAP-70 expression by flow cytometry, serum β2-microglobulin, and immunoglobulin heavy-chain variable gene mutational status. Cytogenetics for targeted chromosome alterations may similarly aid in predicting outcome and guiding early intervention. This article concisely reviews the utility of commonly performed prognostic markers and addresses the laboratory evaluation in patients with incidentally discovered early stage CLL.

Imaging oxytocin × dopamine interactions: an epistasis effect of CD38 and COMT gene variants influences the impact of oxytocin on amygdala activation to social stimuli

Although oxytocin (OT) has become a major target for the investigation of positive social processes, it can be assumed that it exerts its effects in concert with other neurotransmitters. One candidate for such an interaction is dopamine (DA). For both systems, genetic variants have been identified that influence the availability of the particular substance. A variant of the gene coding for the transmembrane protein CD38 (rs3796863), which is engaged in OT secretion, has been associated with OT plasma level. The common catechol-O-methyltransferase (COMT) val158met polymorphism is known to influence COMT activity and therefore the degradation of DA. The present study aimed to investigate OT × DA interactions in the context of an OT challenge study. Hence, we tested the influence of the above mentioned genetic variants and their interaction on the activation of different brain regions (amygdala, VTA, ventral striatum and fusiform gyrus) during the presentation of social stimuli. In a pharmacological cross-over design 55 participants were investigated under OT and placebo (PLA) by means of fMRI. Brain imaging results revealed no significant effects for VTA or ventral striatum. Regarding the fusiform gyrus, we could not find any effects apart from those already described in Sauer et al. (2012). Analyses of amygdala activation resulted in no gene main effect, no gene × substance interaction but a significant gene × gene × substance interaction. While under PLA the effect of CD38 on bilateral amygdala activation to social stimuli was modulated by the COMT genotype, no such epistasis effect was found under OT. Our results provide evidence for an OT × DA interaction during responses to social stimuli. We postulate that the effect of central OT secretion on amygdala response is modulated by the availability of DA. Therefore, for an understanding of the effect of social hormones on social behavior, interactions of OT with other transmitter systems have to be taken into account.

Prognosis Factors in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia is still one of the most common hematologic malignancies. Finding a curative solution is the objective of numerous followed cases and clinical trials. Diagnosis is based on the interlocking of classic elements and newly identified prognostic factors but time to first treatment is still an open issue. CD38, ZAP 70, IgHV gene mutational status and cytogenetic changes are proven negatively influence the evolution of chronic lymphocytic leukemia. Whether through aggressive rapid evolution or by the difficulty of obtaining a complete remission or risk of early relapse, CLL is still important. Adapted to these prognostic factors, combined therapeutic regimens have proved to be effective in achieving a durable complete remission, new agents, with encouraging partial results, being studied. Requiring initial screening, for comparative purposes, a current and growing importance has minimal residual disease; its absence at the end of treatment represents a strong positive prognostic factor.

Dendritic cell populations in patients with self-reported food hypersensitivity

Self-reported hypersensitivity to food is a common condition and many of these patients have indications of intestinal immune activation. Dendritic cells (DCs) are recognized as the most potent antigen-presenting cells involved in both initiating immune responses and maintaining tolerance. The aims of this study were to evaluate the DC populations with their phenotype and T cell stimulatory capacity in patients with food hypersensitivity and to study its relationship with atopic disease. Blood samples from 10 patients with self-reported food hypersensitivity, divided into atopic and nonatopic subgroups, and 10 gender- and age-matched healthy controls were analyzed by flow cytometry using the Miltenyi Blood Dendritic cells kit. Monocyte-derived DCs (moDCs) were evaluated concerning their phenotype and T cell stimulatory capacity. DC populations and cell surface markers were not significantly different between patients and healthy controls, but moDCs from atopic patients expressed significantly more CD38 compared to moDCs from nonatopic patients. Moreover, lipopolysaccharide stimulated moDCs from atopic patients produced significantly more interleukin-10 compared to nonatopic patients. CD38 expression was correlated to total serum immunoglobulin E levels. These findings support the notion of immune activation in some patients with self-reported food hypersensitivity. They need to be confirmed in a larger cohort.

Quantification of CD8(+)CD38(+) T lymphocytes by flow cytometry does not represent a good biomarker to monitor the reactivation of cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Infection/reactivation of cytomegalovirus is a major cause of morbidity and mortality in immunocompromised transplant patients. It has already been observed in kidney and liver transplantation patients that cytomegalovirus disease is accompanied by significant increases in circulating CD8(+)CD38(+) T lymphocytes. There are no reports that study CD8(+)CD38(+) T lymphocytes to monitor/diagnose cytomegalovirus disease in hematopoietic stem cell transplantation patients.

OBJECTIVE

The aim of this study was to evaluate some cellular activation markers on circulating mononuclear cells (CD38 and HLA-DR) in patients submitted to hematopoietic stem cell transplantation and to establish any correlation with cytomegalovirus disease as diagnosed by antigenemia.

METHODS

Blood samples of 15 transplant patients were analyzed by flow cytometry using anti-CD3, anti-CD4, anti-CD8, anti-CD38, CD16, CD56 and anti-HLA-DR monoclonal antibodies and the results were evaluated in respect to cytomegalovirus antigenemia measured by indirect immunofluorescence. Minitab for Windows was used for statistical analysis and a p-value < 0.05 was considered significant.

RESULTS

Patients with positive antigenemia did not show any significant increase in the percentages of cells expressing the CD38 or HLADR activation markers when compared to patients with negative antigenemia. On the contrary, all patients showed high percentages of these cells independent of the presence of cytomegalovirus disease.

CONCLUSIONS

This study suggests that the investigation of these lymphocyte sub-populations in patients submitted to hematopoietic stem cell transplantation does not seem to contribute to the early identification of cytomegalovirus disease.

High lymphoid enhancer-binding factor-1 expression is associated with disease progression and poor prognosis in chronic lymphocytic leukemia

We determined lymphoid enhancer-binding factor-1 (LEF1) mRNA expression in 112 chronic lymphocytic leukemia (CLL) samples and assessed correlations with the prognostic markers ZAP70 and CD38, Binet stages, the percentage of lymphocytes in the peripheral blood, and fibromodulin (FMOD) transcripts. The mean LEF1 relative expression ratios (RER) were 53.72 and 37.10 in ZAP70-positive and ZAP70-negative patients, respectively (P=0.004). However, we did not observe a significant difference in LEF1 expression between CD38-positive and CD38-negative patients. Moreover, patients requiring treatment showed a mean LEF1 RER of 85.61 whereas patients in recently diagnosed Binet A stage had a mean of only 22.01 (P<0.001). We also found significant correlations of LEF1 with the percentage of lymphocytes and FMOD expression. Our results suggest that high LEF1 expression is associated with poor prognosis and disease progression. Thus, LEF1 might be involved in the process of disease progression and possibly can serve as a molecular parameter for risk assessment and/or monitoring of CLL.

Comparison of Bcl-2, CD38 and ZAP-70 Expression in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) was previously considered a uniform disease characterized by autonomous over-expression of bcl-2. Recently the pathogenic role of bcl-2 has been questioned and attention has turned to prognostic subtypes of CLL differing in CD38 and ZAP-70 expression. However, the relationship between bcl-2 and CD38 or ZAP-70 expression remains uncertain and was investigated using flow cytometric immunophenotyping of 50 CLL specimens. CLL cells were consistently bcl-2 positive but varied in expression level: mean fluorescence intensity (MFI) 45-152. Although there was no significant difference in bcl-2 expression between CD38 or ZAP-70 positive and negative specimens, an inverse correlation was identified between percentage of CD38 positive B-cells and bcl-2 MFI when all (p<0.03, r(2)=0.10) and peripheral blood (p<0.004, r(2)=0.27) samples were analyzed. While bcl-2 levels do not appear to be a major discriminator between indolent and more aggressive subtypes of CLL, CD38 and bcl-2 expression appear to be interrelated.