The Banff 2017 Kidney Meeting Report: Revised diagnostic criteria for chronic active T cell-mediated rejection, antibody-mediated rejection, and prospects for integrative endpoints for next-generation clinical trials.

The kidney sessions of the 2017 Banff Conference focused on 2 areas: clinical implications of inflammation in areas of interstitial fibrosis and tubular atrophy (i-IFTA) and its relationship to T cell-mediated rejection (TCMR), and the continued evolution of molecular diagnostics, particularly in the diagnosis of antibody-mediated rejection (ABMR). In confirmation of previous studies, it was independently demonstrated by 2 groups that i-IFTA is associated with reduced graft survival. Furthermore, these groups presented that i-IFTA, particularly when involving >25% of sclerotic cortex in association with tubulitis, is often a sequela of acute TCMR in association with underimmunosuppression. The classification was thus revised to include moderate i-IFTA plus moderate or severe tubulitis as diagnostic of chronic active TCMR. Other studies demonstrated that certain molecular classifiers improve diagnosis of ABMR beyond what is possible with histology, C4d, and detection of donor-specific antibodies (DSAs) and that both C4d and validated molecular assays can serve as potential alternatives and/or complements to DSAs in the diagnosis of ABMR. The Banff ABMR criteria are thus updated to include these alternatives. Finally, the present report paves the way for the Banff scheme to be part of an integrative approach for defining surrogate endpoints in next-generation clinical trials.

Molecular Assessment of Microcirculation Injury in Formalin-Fixed Human Cardiac Allograft Biopsies With Antibody-Mediated Rejection.

Precise diagnosis of antibody-mediated rejection (AMR) in cardiac allograft endomyocardial biopsies (EMBs) remains challenging. This study assessed molecular diagnostics in human EMBs with AMR. A set of 34 endothelial, natural killer cell and inflammatory genes was quantified in 106 formalin-fixed, paraffin-embedded EMBs classified according to 2013 International Society for Heart and Lung Transplantation (ISHLT) criteria. The gene set expression was compared between ISHLT diagnoses and correlated with donor-specific antibody (DSA), endothelial injury by electron microscopy (EM) and prognosis. Findings were validated in an independent set of 57 EMBs. In the training set (n = 106), AMR cases (n = 70) showed higher gene set expression than acute cellular rejection (ACR; n = 21, p < 0.001) and controls (n = 15, p < 0.0001). Anti-HLA DSA positivity was associated with higher gene set expression (p = 0.01). Endothelial injury by electron microscopy strongly correlated with gene set expression, specifically in AMR cases (r = 0.62, p = 0.002). Receiver operating characteristic curve analysis for diagnosing AMR showed greater accuracy with gene set expression (area under the curve [AUC] = 79.88) than with DSA (AUC = 70.47) and C4d (AUC = 70.71). In AMR patients (n = 17) with sequential biopsies, increasing gene set expression was associated with inferior prognosis (p = 0.034). These findings were confirmed in the validation set. In conclusion, biopsy-based molecular assessment of antibody-mediated microcirculation injury has the potential to improve diagnosis of AMR in human cardiac transplants.

The XIIIth Banff Conference on Allograft Pathology: The Banff 2015 Heart Meeting Report: Improving Antibody-Mediated Rejection Diagnostics: Strengths, Unmet Needs, and Future Directions.

The 13th Banff Conference on Allograft Pathology was held in Vancouver, British Columbia, Canada from October 5 to 10, 2015. The cardiac session was devoted to current diagnostic issues in heart transplantation with a focus on antibody-mediated rejection (AMR) and small vessel arteriopathy. Specific topics included the strengths and limitations of the current rejection grading system, the central role of microvascular injury in AMR and approaches to semiquantitative assessment of histopathologic and immunophenotypic indicators, the role of AMR in the development of cardiac allograft vasculopathy, the important role of serologic antibody detection in the management of transplant recipients, and the potential application of new molecular approaches to the elucidation of the pathophysiology of AMR and potential for improving the current diagnostic system. Herein we summarize the key points from the presentations, the comprehensive, open and wide-ranging multidisciplinary discussion that was generated, and considerations for future endeavors.

Real Time Central Assessment of Kidney Transplant Indication Biopsies by Microarrays: The INTERCOMEX Study.

The authors conducted a prospective trial to assess the feasibility of real time central molecular assessment of kidney transplant biopsy samples from 10 North American or European centers. Biopsy samples taken 1 day to 34 years posttransplantation were stabilized in RNAlater, sent via courier overnight at ambient temperature to the central laboratory, and processed (29 h workflow) using microarrays to assess T cell- and antibody-mediated rejection (TCMR and ABMR, respectively). Of 538 biopsy samples submitted, 519 (96%) were sufficient for microarray analysis (average length, 3 mm). Automated reports were generated without knowledge of histology and HLA antibody, with diagnoses assigned based on Molecular Microscope Diagnostic System (MMDx) classifier algorithms and signed out by one observer. Agreement between MMDx and histology (balanced accuracy) was 77% for TCMR, 77% for ABMR, and 76% for no rejection. A classification tree derived to provide automated sign-outs predicted the observer sign-outs with >90% accuracy. In 451 biopsy samples where feedback was obtained, clinicians indicated that MMDx more frequently agreed with clinical judgment (87%) than did histology (80%) (p = 0.0042). In 81% of feedback forms, clinicians reported that MMDx increased confidence in management compared with conventional assessment alone. The authors conclude that real time central molecular assessment is feasible and offers a useful new dimension in biopsy interpretation. ClinicalTrials.gov NCT#01299168.

Late Failing Heart Allografts: Pathology of Cardiac Allograft Vasculopathy and Association With Antibody-Mediated Rejection.

In heart transplantation, there is a lack of robust evidence of the specific causes of late allograft failure. We hypothesized that a substantial fraction of failing heart allografts may be associated with antibody-mediated injury and immune-mediated coronary arteriosclerosis. We included all patients undergoing a retransplantation for late terminal heart allograft failure in three referral centers. We performed an integrative strategy of heart allograft phenotyping by assessing the heart vascular tree including histopathology and immunohistochemistry together with circulating donor-specific antibodies. The main analysis included 40 explanted heart allografts patients and 402 endomyocardial biopsies performed before allograft loss. Overall, antibody-mediated rejection was observed in 19 (47.5%) failing heart allografts including 16 patients (40%) in whom unrecognized previous episodes of subclinical antibody-mediated rejection occurred 4.5 ± 3.5 years before allograft loss. Explanted allografts with evidence of antibody-mediated rejection demonstrated higher endothelitis and microvascular inflammation scores (0.89 ± 0.26 and 2.25 ± 0.28, respectively) compared with explanted allografts without antibody-mediated rejection (0.42 ± 0.11 and 0.36 ± 0.09, p = 0.046 and p < 0.0001, respectively). Antibody-mediated injury was observed in 62.1% of failing allografts with pure coronary arteriosclerosis and mixed (arteriosclerosis and atherosclerosis) pattern, while it was not observed in patients with pure coronary atherosclerosis (p = 0.0076). We demonstrate that antibody-mediated rejection is operating in a substantial fraction of failing heart allografts and is associated with severe coronary arteriosclerosis. Unrecognized subclinical antibody-mediated rejection episodes may be observed years before allograft failure.

Inflammatory cell burden and phenotype in endomyocardial biopsies with antibody-mediated rejection (AMR): a multicenter pilot study from the AECVP.

This multicenter case-controlled pilot study evaluated myocardial inflammatory burden (IB) and phenotype in endomyocardial biopsies (EMBs) with and without pathologic antibody-mediated rejection (pAMR). Sixty-five EMBs from five European heart transplant centers were centrally reviewed as positive (grade 2, n = 28), suspicious (grade 1, n = 7) or negative (n = 30) for pAMR. Absolute counts of total, intravascular (IV) and extravascular (EV) immunophenotyped mononuclear cells were correlated with pAMR grade, capillary C4d deposition, donor specific antibody (DSA) status and acute cellular rejection (ACR). In pAMR+ biopsies, equivalent number of IV CD3+ T lymphocytes (23 ± 4/0.225 mm(2) ) and CD68+ macrophages (21 ± 4/0.225 mm(2) ) were seen. IB and cell phenotype correlated with pAMR grade, C4d positivity and DSA positivity (p < 0.0001). High numbers of IV T lymphocytes were associated with low grade ACR (p = 0.002). In late-occurring AMR EV plasma cells occurring in 34% of pAMR+ EMBs were associated with higher IB. The IB in AMR correlated with pAMR+, C4d positivity and DSA positivity. In pAMR+ equivalent numbers of IV T lymphocytes and macrophages were found. The presence of plasma cells was associated with a higher IB and occurrence of pAMR late after transplantation.

Recurrent 2,8-dihydroxyadenine nephropathy: a rare but preventable cause of renal allograft failure.

Adenine phosphoribosyltransferase (APRT) deficiency is a rare autosomal recessive enzyme defect of purine metabolism that usually manifests as 2,8-dihydroxyadenine (2,8-DHA) nephrolithiasis and more rarely chronic kidney disease. The disease is most often misdiagnosed and can recur in the renal allograft. We analyzed nine patients with recurrent 2,8-DHA crystalline nephropathy, in all of whom the diagnosis had been missed prior to renal transplantation. The diagnosis was established at a median of 5 (range 1.5-312) weeks following the transplant procedure. Patients had delayed graft function (n=2), acute-on-chronic (n=5) or acute (n=1) allograft dysfunction, whereas one patient had normal graft function at the time of diagnosis. Analysis of allograft biopsies showed birefringent 2,8-DHA crystals in renal tubular lumens, within tubular epithelial cells and interstitium. Fourier transformed infrared microscopy confirmed the diagnosis in all cases, which was further supported by 2,8-DHA crystalluria, undetectable erythrocyte APRT enzyme activity, and genetic testing. With allopurinol therapy, the allograft function improved (n=7), remained stable (n=1) or worsened (n=1). At last follow-up, two patients had experienced allograft loss and five had persistent chronic allograft dysfunction. 2,8-DHA nephropathy is a rare but underdiagnosed and preventable disorder that can recur in the renal allograft and may lead to allograft loss.

Pretransplant sensitization against angiotensin II type 1 receptor is a risk factor for acute rejection and graft loss.

The angiotensin II type 1 receptor (AT1R) is an emerging target of functional non-HLA antibodies (Ab). We examined the potential of determining the degree of presensitization against AT1R as a risk factor for graft survival and acute rejection (AR). The study included 599 kidney recipients between 1998 and 2007. Serum samples were analyzed in a blinded fashion for anti-AT1R antibodies (AT1R-Abs) using a quantitative solid-phase assay. A threshold of AT1R-Ab levels was statistically determined at 10 U based on the time to graft failure. An extended Cox model determined risk factors for occurrence of graft failure and a first AR episode. AT1R-Abs >10 U were detected in 283 patients (47.2%) before transplantation. Patients who had a level of AT1R-Abs >10 U had a 2.6-fold higher risk of graft failure from 3 years posttransplantation onwards (p = 0.0005) and a 1.9-fold higher risk of experiencing an AR episode within the first 4 months of transplantation (p = 0.0393). Antibody-mediated rejection (AMR) accounted for 1/3 of AR, whereby 71.4% of them were associated with >10 U of pretransplant AT1R-Abs. Pretransplant anti-AT1R-Abs are an independent risk factor for long-term graft loss in association with a higher risk of early AR episodes.

The mast cell: A Janus in kidney transplants.

Mast cells (MCs) are innate immune cells with a versatile set of functionalities, enabling them to orchestrate immune responses in various ways. Aside from their known role in allergy, they also partake in both allograft tolerance and rejection through interaction with regulatory T cells, effector T cells, B cells and degranulation of cytokines and other mediators. MC mediators have both pro- and anti-inflammatory actions, but overall lean towards pro-fibrotic pathways. Paradoxically, they are also seen as having potential protective effects in tissue remodeling post-injury. This manuscript elaborates on current knowledge of the functional diversity of mast cells in kidney transplants, combining theory and practice into a MC model stipulating both protective and harmful capabilities in the kidney transplant setting.

Corrigendum: The mast cell: A Janus in kidney transplants.

[This corrects the article DOI: 10.3389/fimmu.2023.1122409.].

SMILE silencing and PMA activation gene networks in HeLa cells: comparison with kidney transplantation gene networks.

Recent findings indicated that the SMILE gene may be involved in kidney graft operational tolerance in human. This gene was found to be up-regulated in blood from patients with a well functioning kidney transplant in the absence of immunosuppression compared to other transplanted recipients with clinically different status. A microarray study of SMILE knock-down and phorbol 12-myristate 13-acetate (PMA) activation in HeLa cells was herein compared to our earlier analysis based on microarray data of kidney allograft tolerance and rejection in humans and in a rat model of allograft transplantation to determine possible new genes and gene networks involved in kidney transplantation. The nearest neighbors at the intersection of the SMILE knock-down network with the human tolerance/rejection networks are shown to be NPHS1 and ARRB2, the former (Nephrin) being involved in kidney podocyte function, and the decrease of the latter (Arrestin ß2) being recently shown to be involved in monocyte activation during acute kidney allograft rejection in rat. Moreover, another one of the neighbors at the intersection of SMILE network and tolerance/rejection networks is XBP-1, that we report previously to be increased, at a transcript level, after ER stress in SMILE silenced cells. Finally, in this study, we also show that topological properties (both local and global) of joint SMILE knock-down network-tolerance/rejection networks and joint PMA activation network-tolerance/rejection networks in rat and human are essentially different, likely due to the inherent nature of the gene SMILE and the mitogen PMA, that do not act the same way on genes and do not interfere the same way on networks. We also show that interestingly SMILE networks contain more feed-forward loop (FFL) motifs and thus SMILE calls for a more fine-tuned genetic regulation.

Donor-specific antibodies accelerate arteriosclerosis after kidney transplantation.

In biopsies of renal allografts, arteriosclerosis is often more severe than expected based on the age of the donor, even without a history of rejection vasculitis. To determine whether preformed donor-specific antibodies (DSAs) may contribute to the severity of arteriosclerosis, we examined protocol biopsies from patients with (n=40) or without (n=59) DSA after excluding those with any evidence of vasculitis. Among DSA-positive patients, arteriosclerosis significantly progressed between month 3 and month 12 after transplant (mean Banff cv score 0.65 ± 0.11 to 1.12 ± 0.10, P=0.014); in contrast, among DSA-negative patients, we did not detect a statistically significant progression during the same timeframe (mean Banff cv score 0.65 ± 0.11 to 0.81 ± 0.10, P=not significant). Available biopsies at later time points supported a rate of progression of arteriosclerosis in DSA-negative patients that was approximately one third that in DSA-positive patients. Accelerated arteriosclerosis was significantly associated with peritubular capillary leukocytic infiltration, glomerulitis, subclinical antibody-mediated rejection, and interstitial inflammation. In conclusion, these data support the hypothesis that donor-specific antibodies dramatically accelerate post-transplant progression of arteriosclerosis.

Very late heart transplant rejection is associated with microvascular injury, complement deposition and progression to cardiac allograft vasculopathy.

In heart transplants, the significance of very late rejection (after 7 years post-transplant, VLR) detected by routine endomyocardial biopsies (EMB) remains uncertain. Here, we assessed the prevalence, histopathological and immunological phenotype, and outcome of VLR in clinically stable patients. Between 1985 and 2009, 10 662 protocol EMB were performed at our institution in 398 consecutive heart transplants recipients. Among the 196 patients with >7-year follow-up, 20 (10.2%) presented subclinical ≥3A/2R-ISHLT rejection. The VLR group was compared to a matched control group of patients without rejection. All biopsies were stained for C4d/C3d/CD68 with sera screened for the presence of donor-specific antibodies (DSAs). In addition to cellular infiltrates with myocyte damage, 60% of VLR patients had evidence of intravascular macrophages. C4d and/or C3d-capillary deposition was found in 55% VLR EMB. All cases of VLR associated with microcirculation injury had DSAs (mean DSA(max) -MFI = 1751 ± 583). This entity was absent from the control group (p < 0.0001). Finally, after a similar follow-up postreference EMB of 6.4 ± 1 years, the mean of CAV grade was 0.76 ± 0.18 in the control group compared to 2.06 ± 0.26 in the VLR group respectively, p = 0.001). There was no difference in patient survival between study and control groups. In conclusion, VLR is frequently associated with complement-cascade activation, microvascular injury and DSA, suggesting an antibody-mediated process. VLR is associated with a dramatic progression to severe CAV in long-term follow-up.

Outcome of subclinical antibody-mediated rejection in kidney transplant recipients with preformed donor-specific antibodies.

This study describes clinical relevance of subclinical antibody-mediated rejection (SAMR) in a cohort of 54 DSA-positive kidney transplant recipients receiving a deceased donor. In 3 months screening biopsies, 31.1% of patients met the criteria of SAMR. A total of 48.9% had an incomplete form of SAMR (g+/ptc+/C4d-negative) whereas 20% had no humoral lesions. Patients with SAMR at 3 months had at 1 year: a higher C4d score, ptc score, and arteriosclerosis score, higher rate of IFTA (100% vs. 33.3%, p < 0.01) and a higher rate of transplant glomerulopathy (43% vs. 0%, p = 0.02) compared to patients without 3-month SAMR. Patients with SAMR at 3 months exhibited at 1 year a higher class II MFImax-DSA and a lower mGFR compared to patients without SAMR (39.2 +/- 13.9 vs. 61.9 +/- 19.2 mL/min/1.73 m(2) respectively, p < 0.01). The group of patients with C4d-negative SAMR at 3 months developed more ptc and IFTA lesions, and lower GFR at 1 year in comparison to biopsies without humoral lesions. SAMR is a frequent entity in KTR with preexisting DSAs and promotes subsequent GFR impairment and development of chronic AMR. C4d-negative SAMR patients displayed an intermediate course between the no-SAMR group and the C4d+ SAMR group. Screening biopsies may be useful to recognize patients more likely to develop SAMR.

Combined heart and kidney transplantation in a patient with Fabry disease in the enzyme replacement therapy era.

Fabry disease (FD) is an X-linked genetic disease, resulting from the deficiency of alpha-galactosidase A, a lysosomal enzyme responsible for the cleavage of glycosphingolipids. In absence of enzyme replacement therapy (ERT), globotriaosylceramide (Gb3) accumulates in tissue, leading to progressive organ damage with severe renal, cardiac and central nervous system complications. We herein describe the first case of successful combined and simultaneous heart and kidney transplantation in a young male patient with FD complicated by end-stage renal disease and severe heart failure not responding to late-onset ERT. Combined heart and kidney transplantation can be recommended for Fabry patients with end-stage renal disease and overt hypertrophic cardiomyopathy, severe ischemic or valvular heart disease.

Altered nephrogenesis due to maternal diabetes is associated with increased expression of IGF-II/mannose-6-phosphate receptor in the fetal kidney.

We have recently demonstrated that the exposure to hyperglycemia in utero impairs nephrogenesis in rat fetuses (Amri K et al., Diabetes 48:2240-2245, 1999). Diabetic pregnancy is commonly associated with alterations in the IGF system in fetal tissues. It has also been shown that both IGF-I and IGF-II are produced within developing metanephros and promote renal organogenesis. Therefore, we investigated the effect of maternal diabetes on IGFs and their receptors in developing fetal rat kidney. Diabetes was induced in pregnant rats by a single injection of streptozotocin on day 0 of gestation. We measured the amounts of IGF and their receptors, both proteins and mRNAs, in the metanephroi of fetuses issued from diabetic subjects and in age-matched fetuses from control subjects (14-20 days of gestation). IGF-II was produced throughout fetal nephrogenesis, whereas IGF-I protein was not detected, suggesting a critical role of IGF-II in kidney development. Fetal exposure to maternal diabetes caused no change in IGF production in the early stages of nephrogenesis. Similarly, the amounts of IGF-I receptor and insulin receptor were not altered. By contrast, there was an increase in production of IGF-II/mannose-6-phosphate receptor throughout nephrogenesis. Because this receptor plays an essential role in regulating the action of IGF-II, the altered nephrogenesis in fetuses exposed to maternal diabetes may be linked to a decrease in IGF-II bioavailability.

Immunomodulation of autoimmune and inflammatory diseases with intravenous immunoglobulin.

Intravenous immunoglobulin (IVIg) has been used in the treatment of primary and secondary antibody deficiencies for over two decades. Since the early 1980s, the therapeutic efficacy of IVIg has been established in idiopathic thrombocytopenic purpura, Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, myasthenia gravis, dermatomyositis and Kawasaki syndrome, and the prevention of graft versus host disease in recipients of allogeneic bone marrow transplants. Its use has also been reported in a large number of other autoimmune and systemic inflammatory conditions. In this review, we discuss the mechanisms by which IVIg exerts immunomodulatory effects in immune pathologies.

Long-term efficacy of combination therapy with interferon-alpha 2b and ribavirin for severe chronic hepatitis C in HIV-infected patients.

BACKGROUND: We have assessed the long-term efficacy and safety of a combination therapy of interferon alpha-2b (IFN) and ribavirin (RBV) for the treatment of severe chronic hepatitis C in co-infected HIV-seropositive patients in an open prospective study. METHODS: Fifty-one patients were treated for 12 months. Mean baseline CD4 cell count, alanine aminotransferase and aspartate aminotransferase were 412 +/- 232 x 106/l, 113 +/- 75 IU/l and 111 +/- 84 IU/l respectively. The mean Knodell score was 11.5 +/- 2.1 with 28 patients (55%) exhibiting histological evidence of active cirrhosis. RESULTS: Fifteen (29%) patients discontinued the treatment prematurely because of adverse events. An end of treatment response (ETR) as defined by the lack of detectable hepatitis C virus (HCV) RNA in plasma at the end of treatment was achieved in 15 patients (29%). A sustained virological response (SVR), defined by the lack of detectable HCV RNA in plasma 6 months after completion of combination therapy, was achieved in 11 patients (21%). The HCV genotype 3a was associated with ETR and SVR (P = 0.002 and P = 0.003, respectively). HCV viraemia at baseline was lower in patients who achieved SVR and ETR than in those who did not (6.7 +/- 7.8 versus 24 +/- 26.7 x 10(6) genome equivalents/ml, P = 0.03 and 14.3 +/- 28.7 versus 22.5 +/- 23, P = 0.05, respectively). CONCLUSION: Our results indicate that combination therapy with IFN and RBV is effective in approximately 20% of co-infected patients with severe liver disease.

Efficacy and safety of combination therapy with interferon-alpha2b and ribavirin for chronic hepatitis C in HIV-infected patients.

OBJECTIVES: To evaluate the efficacy and safety of a combination therapy of interferon-alpha2b (IFN) and ribavirin for the treatment of chronic hepatitis C in HIV-seropositive patients. DESIGN: Open prospective trial. METHODS: Twenty patients co-infected with hepatitis C virus (HCV) and HIV, with a mean CD4 cell count of 350 +/- 153 x 10(6)/l were treated with IFN (3 MU three times per week) in combination with ribavirin (500 mg or 600 mg twice a day) for 6 months. Tolerance and efficacy were monitored at weeks 12 (month 3) and 24 (month 6). The primary endpoint was a complete virological response, as defined by the lack of detectable HCV RNA in serum. RESULTS: Baseline values of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were 121 +/- 72 IU/l and 75 +/- 67 IU/l, respectively. The total Knodell score was 10.4 +/- 2.4, with nine patients showing histological evidence of active cirrhosis (45%). All patients exhibited circulating HCV RNA. The treatment was well tolerated, with no impact on the course of HIV infection. After 6 months of combination therapy with IFN and ribavirin, 10 patients (50%) exhibited no further detectable HCV RNA viraemia, seven of whom achieved undetectable viraemia at month 3. Levels of ALT and AST decreased after 6 months of treatment from a mean of 121 +/- 72 to 51 +/- 40 IU/l and from a mean of 129 +/- 58 IU/l to 68 +/- 61 IU/l, respectively (P < 0.0002 and P < 0.0001). CONCLUSION: Our results indicate that combination therapy with IFN and ribavirin is effective in 50% of cases in clearing serum HCV RNA and may thus provide effective means of therapy in HIV-HCV-coinfected patients as initial treatment or in patients who have previously failed IFN monotherapy.

Splenic marginal zone lymphoma with or without plasmacytic differentiation.

We report a series of 31 cases of splenic marginal zone lymphomas with an enlarged spleen and a multimicronodular macroscopic pattern. Two groups, A and B, were distinguished based on the presence (A) or absence (B) of a lymphoplasmacytic component with monoclonal immunoglobulin expression in the cytoplasm. There were no differences between the groups as far as age, sex, spleen weight, and progression. The only difference was the presence in group A of a monoclonal serum component and autoimmune disorders, particularly autoimmune hemolytic anemia. In most cases in which a liver and/or bone marrow biopsy was performed, lymphomatous infiltration was detected. Seven cases had a seric monoclonal IgM of 5 g/L or more and liver or bone marrow infiltration, corresponding to the definition of Waldenstrom's macroglobulinemia. Lymphoma cells had a monocytoid, centrocytoid and, in group A, lymphoplasmacytic morphology. The lymphomatous cells were positive for CD20, CD45 RA, and bcl-2. They expressed IgD in 9 cases, partially in 6, and were negative for IgD in 9 of the 24 cases studied. Progression seems to be slow, with a long survival. Three patients presented with transformation into a large B-cell lymphoma, which was responsible for death in two patients.