Exosomes from heat‐stressed tumour cells inhibit tumour growth by converting regulatory T cells to Th17 cells via IL‐6

Exosomes derived from heat‐stressed tumour cells (HS‐TEXs), which contain abundant heat shock protein (HSP) 70, strongly induce antitumour immune responses. HSP70‐induced interleukin (IL)‐6 promotes IL‐17 expression and causes rejection of established prostate tumours. However, it remains unclear whether HS‐TEXs exhibit antitumour effects by converting regulatory T cells (T_regs) into T helper type 17 (Th17) cells. In this study, we found that compared with TEXs, HS‐TEXs were more potent in stimulating secretion of IL‐6 from dendritic cells. In vitro, IL‐6 blocked tumour cell‐derived transforming growth factor beta 1‐induced T_reg differentiation and promoted Th17 cell differentiation. HS‐TEXs exerted strong antitumour effects, converting T_regs into Th17 cells with high efficiency, a process that was entirely dependent upon IL‐6. Neutralization of IL‐17 completely abolished the antitumour effect of TEXs, but only partially inhibited that of HS‐TEXs. In addition, we found higher levels of IL‐6 and IL‐17 in serum from tumour patients treated with hyperthermia, and an increase in Th17 cells and a decrease in T_regs was detected in peripheral blood mononuclear cells isolated from these patients after hyperthermia. Therefore, our results demonstrate that HS‐TEXs possess a powerful capacity to convert immunosuppressive T_regs into Th17 cells via IL‐6, which contributes to their potent antitumour effect.     

The effect of mesenchymal stem cells on dynamic changes of T cell subsets in experimental autoimmune uveoretinitis

Mesenchymal stem cells (MSCs) are being explored extensively as a promising treatment for autoimmune diseases. We have recently reported that MSCs could ameliorate experimental autoimmune uveoretinitis (EAU) in rats. In this study, we examined further the effects of MSCs on the dynamics of T cell subsets in both eye and spleen and their cytokine production during the course of EAU. We focused on when and where the MSCs had inhibitory effects on T helper type 1 (Th1) and Th17 cells and how long the inhibitory effect lasted, in order to provide more mechanistic evidence for MSCs on the treatment of uveitis. Compared to the control group, administration of MSCs decreased the production of Th1 and Th17 cytokines significantly, while the production of Th2 and regulatory T cell (T_reg) cytokines [interleukin (IL)‐10 and transforming growth factor (TGF)‐β] was elevated during the entire course of EAU. Correspondingly, the dynamic levels of IL‐17 in the aqueous humour (AqH) were reduced in MSC‐treated rats. Moreover, the ratio of Th17/T_reg cells in both spleen and eye was decreased. These results provide powerful evidence that MSCs can regulate negatively both Th1 and Th17 responses and restore the balance of Th17/T_regs in the whole course of EAU, which is important for the regression of the disease.     

Ovarian cancer stem cells promote tumour immune privilege and invasion via CCL5 and regulatory T cells

Emerging evidence indicates a link between the increased proportion of regulatory T cells (T_regs) and reduced survival in patients who have been diagnosed with cancer. Cancer stem cells (CSCs) have been indicated to play a vital role in tumour initiation, drug resistance and recurrence. However, the relationship between T_regs and CSCs remains largely unknown. Here, we sorted out ovarian cancer stem‐like side population (SP) cells and CD133⁺ cells to investigate the influence of ovarian CSCs on T_regs. Among the various immune‐related molecules that we assessed, C‐C motif chemokine ligand 5 (CCL5) was the most elevated in ovarian CSCs relative to that in the non‐CSCs. The expression of its receptor, C‐C motif chemokine receptor 5 (CCR5), was also increased on the surface of T_regs in ovarian cancer patients. This receptor‐ligand expression profile indicated that ovarian CSCs recruit T_regs via CCL5–CCR5 interactions. We further assessed the expression of interleukin (IL)‐10 in T_regs cultured with different cancer cells. T_regs cultured in conditioned medium (CM) from ovarian CD133⁺ cells expressed a higher level of IL‐10 than T_regs cultured in CM from CD133^– cells, indicating that T_regs exert pronounced immune‐inhibitory functions in CSC‐rich environments. Furthermore, co‐culture with ovarian cancer cell lines induced the expression of matrix metalloproteinase‐9 (MMP9) in T_regs which, in turn, enhanced the degradation of the extracellular matrix and enabled the invasion of tumour cells, thereby facilitating tumour metastasis. For the first time, to our knowledge, our findings describe the relationship between ovarian CSCs and T_regs, and demonstrated that these two cell populations co‐operate to promote tumour immune tolerance and enhance tumour progression.     

Exacerbation of spontaneous autoimmune nephritis following regulatory T cell depletion in B cell lymphoma 2‐interacting mediator knock‐out mice

Regulatory T cells (T_regs) have been recognized as central mediators for maintaining peripheral tolerance and limiting autoimmune diseases. The loss of T_regs or their function has been associated with exacerbation of autoimmune disease. However, the temporary loss of T_regs in the chronic spontaneous disease model has not been investigated. In this study, we evaluated the role of T_regs in a novel chronic spontaneous glomerulonephritis model of B cell lymphoma 2‐interacting mediator (Bim) knock‐out mice by transient depleting T_regs. Bim is a pro‐apoptotic member of the B cell lymphoma 2 (Bcl‐2) family. Bim knock‐out (Bim^–/–) mice fail to delete autoreactive T cells in thymus, leading to chronic spontaneous autoimmune kidney disease. We found that T_reg depletion in Bim^–/– mice exacerbated the kidney injury with increased proteinuria, impaired kidney function, weight loss and greater histological injury compared with wild‐type mice. There was a significant increase in interstitial infiltrate of inflammatory cells, antibody deposition and tubular damage. Furthermore, the serum levels of cytokines interleukin (IL)?2, IL‐4, IL‐6, IL‐10, IL‐17α, interferon (IFN)‐γ and tumour necrosis factor (TNF)‐α were increased significantly after T_reg depletion in Bim^–/– mice. This study demonstrates that transient depletion of T_regs leads to enhanced self‐reactive T effector cell function followed by exacerbation of kidney disease in the chronic spontaneous kidney disease model of Bim‐deficient mice.     

Th17, synchronically increased with Tregs and Bregs,promoted by tumour cells via cell‐contact in primary hepatic carcinoma

Documented reports about T helper type 17 (Th17) cells have revealed that Th17 plays a critical role in inflammation and autoimmunity diseases. However, the role of Th17 in cancer remains contradictory. The interplay between Th17 and tumour cells in the tumour microenvironment of primary hepatic carcinoma (PHC) needs to be explored further and the relationship between Th17, regulatory T cells (T_regs) and regulatory B cells (B_regs) has not been defined completely. In this study, numerous experiments were undertaken to elucidate the interaction of Th17 and T_reg/B_reg cells involved in PHC. Our work demonstrated that an increased Th17 was detected in the peripheral circulation and in tumour tissues in PHC patients. In addition, increases in peripheral blood Th17 corresponded with tumour–node–metastasis (TNM) stage progression. Also, further studies indicated that Th17 cells were promoted by tumour cells in the PHC tumour microenvironment through both contact‐dependent and ‐independent mechanisms, but cell‐contact played the major important role in promoting the production and proliferation of Th17. When isolated CD4⁺CD25⁺CD127^low T_regs and CD4⁺CD25^–CD127⁺ non‐T_regs were cultured with autologous tumour cells, it implied that the phenotype of Th17 and T_regs was modified by tumour cells in the tumour microenvironment. As well as this, Th17 cells were also found to correlate positively with CD4⁺forkhead box protein 3⁺ T_regs and CD19⁺CD5⁺CD1d^hi B_regs in PHC. Notably, Th17 increased synchronically with T_regs and B_regs in PHC. These findings may provide new clues to reveal the mechanisms of immune escape in PHC.     

Pulmonary sarcoidosis is associated with high‐level inducible co‐stimulator (ICOS) expression on lung regulatory T cells – possible implications for the ICOS/ICOS‐ligand axis in disease course and resolution

Sarcoidosis is a granulomatous inflammatory disorder of unknown aetiology. The increased frequency of activated lung CD4⁺ T cells with a T helper type 1 (Th1) cytokine profile in sarcoidosis patients is accompanied by a reduced proportion and/or impaired function of regulatory T cells (T_regs). Here we evaluated the expression of the inducible co‐stimulator (ICOS) on lung and blood CD4⁺ T cell subsets in sarcoidosis patients with different prognosis, by flow cytometry. Samples from the deep airways were obtained by bronchoalveolar lavage (BAL). We show that T_regs from the inflamed lung of sarcoidosis patients were characterized by a unique ICOS^high phenotype. High‐level ICOS expression was restricted to T_regs from the inflamed lung and was absent in blood T_regs of sarcoidosis patients as well as in lung and blood T_regs of healthy volunteers. In addition, lung T_regs exhibited increased ICOS expression compared to sarcoid‐specific lung effector T cells. Strikingly, ICOS expression on T_regs was in particularly high in the lungs of Löfgren's syndrome (LS) patients who present with acute disease which often resolves spontaneously. Moreover, blood monocytes from LS patients revealed increased ICOS‐L levels compared to healthy donors. Sarcoidosis was associated with a shift towards a non‐classical monocyte phenotype and the ICOS‐L^high phenotype was restricted to this particular monocyte subset. We propose a potential implication of the ICOS/ICOS‐L immune‐regulatory axis in disease activity and resolution and suggest to evaluate further the suitability of ICOS as biomarker for the prognosis of sarcoidosis.     

Two separate effects contribute to regulatory T cell defect in systemic lupus erythematosus patients and their unaffected relatives

Forkhead box P3 (FoxP3)⁺ regulatory T cells (T_regs) are functionally deficient in systemic lupus erythematosus (SLE), characterized by reduced surface CD25 [the interleukin (IL)‐2 receptor alpha chain]. Low‐dose IL‐2 therapy is a promising current approach to correct this defect. To elucidate the origins of the SLE T_reg phenotype, we studied its role through developmentally defined regulatory T cell (T_reg) subsets in 45 SLE patients, 103 SLE‐unaffected first‐degree relatives and 61 unrelated healthy control subjects, and genetic association with the CD25‐encoding IL2RA locus. We identified two separate, uncorrelated effects contributing to T_reg CD25. (1) SLE patients and unaffected relatives remarkably shared CD25 reduction versus controls, particularly in the developmentally earliest CD4⁺FoxP3⁺CD45RO^–CD31⁺ recent thymic emigrant T_regs. This first component effect influenced the proportions of circulating CD4⁺FoxP3^highCD45RO⁺ activated T_regs. (2) In contrast, patients and unaffected relatives differed sharply in their activated T_reg CD25 state: while relatives as control subjects up‐regulated CD25 strongly in these cells during differentiation from naive T_regs, SLE patients specifically failed to do so. This CD25 up‐regulation depended upon IL2RA genetic variation and was related functionally to the proliferation of activated T_regs, but not to their circulating numbers. Both effects were found related to T cell IL‐2 production. Our results point to (1) a heritable, intrathymic mechanism responsible for reduced CD25 on early T_regs and decreased activation capacity in an extended risk population, which can be compensated by (2) functionally independent CD25 up‐regulation upon peripheral T_reg activation that is selectively deficient in patients. We expect that T_reg‐directed therapies can be monitored more effectively when taking this distinction into account.     

Tissue talks: immunophenotype of cells infiltrating the graft explains histological findings and the benefits of belatacept at 10 years

Previously, we found a substantial number of regulatory T cells (T_regs) and fewer senescent and T helper type 17 (Th17) and a decrease in interstitial fibrosis (IF) in 12-month graft biopsies in belatacept versus cyclosporin (CNI)-treated patients [Belatacept Evaluation of Nephroprotection and Efficacy as First-line Immunosuppression Trial (BENEFIT) study]. Seven years after kidney transplantation (KT), mean estimated glomerular filtration rate (eGFR), patient and graft survival were significantly higher with belatacept versus CNI treatment. The aim of this study was to determine whether the immunophenotypes of inflammatory and regulatory cell subsets infiltrating the grafts contribute to the BENEFIT’s clinical findings a decade after KT. Twenty-three adult patients with functionally stable KT treated with belatacept and 10 treated with CNI were enrolled. Biopsies were analyzed by histomorphometry and immunohistochemistry for proliferation, senescence, apoptosis, inflammatory and regulatory cell markers in a blinded manner. Significantly lower percentages of inflammatory/fibrogenic cells [interleukin (IL)-22⁺/Th17/Th2/M1 macrophages] were observed in patients treated with belatacept than in patients treated with CNI. By contrast, remarkably higher percentages of regulatory cells [T_regs/B_regs/ plasmacytoid dendritic regulatory cells (pDC_regs)/M2] were found in belatacept-treated patients than in CNI-treated patients. Conspicuously lower percentages of apoptosis and senescence and higher proliferation markers were found in belatacept-treated patients than in CNI-treated patients. Consequently, there was significantly more inflammation in the microvascular compartments as well as increased tubular atrophy and IF in CNI-treated patients. These findings strongly suggest that regulatory mechanisms, along with the absence of deleterious effects of CNI, contribute to the long-term graft histology and function stability in patients treated with belatacept.     

The influence of bone marrow‐ and synovium‐derived mesenchymal stromal cells from osteoarthritis patients on regulatory T cells in co‐culture

There is increasing evidence that inflammation in the synovium plays a major role in the progression of osteoarthritis (OA). However, the immunogenic properties of mesenchymal stromal cells (MSCs), which are considered to regulate immunity in various diseases, remain largely unknown in OA. The purpose of this study was to determine the influence of MSCs from OA patients on regulatory T cells (T_regs) in an allogeneic co‐culture model. Bone marrow (BM) and synovial membrane (SM) were harvested from hip joints of OA patients and co‐cultured with lymphocytes enriched in CD4⁺CD25⁺CD127^– regulatory T cells (T_reg⁺LC) from healthy donors. T_reg proportions and MSC markers were assessed by flow cytometry. Cytokine levels were assessed after 2 and 5 days of co‐cultivation. Additionally, T_reg⁺LC cultures were analysed in the presence of interleukin (IL)‐6 and MSC‐supernatant complemented medium. B‐MSCs and S‐MSCs were able to retain the T_reg proportion compared to lymphocyte monocultures. T cell–MSC co‐cultures showed a significant increase of IL‐6 compared to MSC cultures. S‐MSCs produced higher amounts of IL‐6 compared to B‐MSCs, both in single and T cell co‐cultures. The effect of retaining the T_reg percentage could be reproduced partially by IL‐6 addition to the medium, but could only be observed fully when using MSC culture supernatants. Our data demonstrate that retaining the T_reg phenotype in MSC–T cell co‐cultures can be mediated by MSC derived from OA patients. IL‐6 plays an important role in mediating these processes. To our knowledge, this study is the first describing the interaction of MSCs from OA patients and T_regs in an allogeneic co‐culture model.     

Elevated circulating Th17 and follicular helper CD4+ T cells in patients with rheumatoid arthritis

It remains not fully elucidated the potential functions of Th17 cells and follicular helper T (Tfh) cells and secreting cytokines in the pathogenesis of rheumatoid arthritis (RA) and their association with disease activity. In this study, the frequencies of Th17 and Tfh cells were determined by flow cytometry, and the levels of interleukin (IL)‐17, IL‐21, and IL‐22 were measured by ELISA in RA patients with different disease activities. The dynamic changes of cell subsets were also detected in response to disease‐modify antirheumatic drugs (DMARDs) therapy. The percentages of CD3⁺CD4⁺IL‐17A⁺ (Th17) cells and CD3⁺CD4⁺CXCR5⁺ICOS^high (Tfh) cells, as well as the concentrations of IL‐17, IL‐21, and IL‐22 were significantly elevated in RA patients than those in healthy individuals. Furthermore, Tfh cells, IL‐21, and IL‐22 in the serum was positively correlated with the values of disease activity score. Concentrations of IL‐21 and IL‐22 in the serum were remarkably reduced following the DMARDs therapies. Our data suggested that Th17 cells, Tfh cells as well as the secreting cytokines may be involved in the pathogenesis of RA. The frequency of circulating Tfh cells and the productions of IL‐21 and IL‐22 were associated with the disease activity of RA patients, and might be potential therapeutic targets for treatment of RA.     

Depletion of regulatory T cells in a hapten-induced inflammation model results in prolonged and increased inflammation driven by T cells

Regulatory T cells (T_regs) are known to play an immunosuppressive role in the response of contact hypersensitivity (CHS), but neither the dynamics of T_regs during the CHS response nor the exaggerated inflammatory response after depletion of T_regs has been characterized in detail. In this study we show that the number of T_regs in the challenged tissue peak at the same time as the ear-swelling reaches its maximum on day 1 after challenge, whereas the number of T_regs in the draining lymph nodes peaks at day 2. As expected, depletion of T_regs by injection of a monoclonal antibody to CD25 prior to sensitization led to a prolonged and sustained inflammatory response which was dependent upon CD8 T cells, and co-stimulatory blockade with cytotoxic T lymphocyte antigen-4-immunoglobulin (CTLA-4-Ig) suppressed the exaggerated inflammation. In contrast, blockade of the interleukin (IL)-10-receptor (IL-10R) did not further increase the exaggerated inflammatory response in the T_reg-depleted mice. In the absence of T_regs, the response changed from a mainly acute reaction with heavy infiltration of neutrophils to a sustained response with more chronic characteristics (fewer neutrophils and dominated by macrophages). Furthermore, depletion of T_regs enhanced the release of cytokines and chemokines locally in the inflamed ear and augmented serum levels of the systemic inflammatory mediators serum amyloid (SAP) and haptoglobin early in the response.     

Immunological monitoring of extracorporeal photopheresis after heart transplantation

Extracorporeal photopheresis (ECP) has been used as a prophylactic and therapeutic option to avoid and treat rejection after heart transplantation (HTx). Tolerance‐inducing effects of ECP such as up‐regulation of regulatory T cells (T_regs) are known, but specific effects of ECP on regulatory T cell (T_reg) subsets and dendritic cells (DCs) are lacking. We analysed different subsets of T_regs and DCs as well as the immune balance status during ECP treatment after HTx. Blood samples were collected from HTx patients treated with ECP for prophylaxis (n = 9) or from patients with histologically proven acute cellular rejection (ACR) of grade ≥ 1B (n = 9), as well as from control HTx patients without ECP (HTxC; n = 7). Subsets of T_regs and DCs as well as different cytokine levels were analysed. Almost 80% of the HTx patients showed an effect to ECP treatment with an increase of T_regs and plasmacytoid DCs (pDCs). The percentage of pDCs before ECP treatment was significantly higher in patients with no ECP effect (26·3% ± 5·6%) compared to patients who showed an effect to ECP (9·8% ± 10·2%; P = 0·011). Analysis of functional subsets of CD4⁺CD25^highCD127^low T_regs showed that CD62L‐, CD120b‐ and CD147‐positive T_regs did not differ between the groups. CD39‐positive T_regs increased during ECP treatment compared to HTxC. ECP‐treated patients showed higher levels for T helper type 1 (Th1), Th2 and Th17 cytokines. Cytokine levels were higher in HTx patients with rejection before ECP treatment compared to patients with prophylactic ECP treatment. We recommend a monitoring strategy that includes the quantification and analysis of T_regs, pDCs and the immune balance status before and up to 12 months after starting ECP.     

Indication for a role of regulatory T cells for the advent of influenza A (H1N1)-related pneumonia

Regulatory T cells (T_regs) have an anti‐inflammatory role. A former study in a limited number of patients found that absolute counts of T_regs increase when infection by the new influenza H1N1 virus is complicated with pneumonia. These results generate the question if H1N1‐related pneumonia is associated with a state of hypo‐inflammation. A total of 135 patients were enrolled with blood sampling within less than 24 h from diagnosis; 23 with flu‐like syndrome; 69 with uncomplicated H1N1‐infection; seven with bacterial pneumonia; and 36 with H1N1‐related pneumonia. T_regs and CD14/HLA‐DR co‐expression were estimated by flow cytometry; concentrations of tumour necrosis factor‐alpha (TNF‐α), of interleukin (IL)‐6 and of soluble triggering receptor expressed on myeloid cells‐1 (sTREM‐1) by an enzyme immunoassay; those of procalcitonin (PCT) by immuno‐time‐resolved amplified cryptate technology assay. Expression of human leucocyte antigen D‐related (HLA‐DR) on monocytes was similar between groups; absolute T_reg counts were greater among patients with H1N1‐related pneumonia than flu‐like syndrome or H1N1‐uncomplicated infection. Serum TNF‐α of patients with bacterial pneumonia was greater than those of other groups, but IL‐10 was similar between groups. Serum PCT was greater among patients with H1N1‐related pneumonia and sTREM‐1 among those with H1N1‐related pneumonia. Regression analysis revealed that the most important factors related with the advent of pneumonia were the existence of underlying illnesses (P = 0·006) and of T_regs equal to or above 16 mm³ (P = 0·013). It is concluded that the advent of H1N1‐related pneumonia is related to an early increase of the absolute T_reg counts. This increase is probably not part of a hypo‐inflammatory state of the host.     

T‐bet regulates differentiation of forkhead box protein 3+ regulatory T cells in programmed cell death‐1‐deficient mice

Programmed cell death‐1 (PD‐1) plays an important role in peripheral T cell tolerance, but whether or not it affects the differentiation of helper T cell subsets remains elusive. Here we describe the importance of PD‐1 in the control of T helper type 1 (Th1) cell activation and development of forkhead box protein 3 (FoxP3⁺) regulatory T cells (T_regs). PD‐1‐deficient T cell‐specific T‐bet transgenic (P/T) mice showed growth retardation, and the majority died within 10 weeks. P/T mice showed T‐bet over‐expression, increased interferon (IFN)‐γ production by CD4⁺ T cells and significantly low FoxP3⁺ T_reg cell percentage. P/T mice developed systemic inflammation, which was probably induced by augmented Th1 response and low FoxP3⁺ T_reg count. The study identified a unique, previously undescribed role for PD‐1 in Th1 and T_reg differentiation, with potential implication in the development of Th1 cell‐targeted therapy.     

Interleukin‐2 treatment reverses effects of cAMP‐responsive element modulator α‐over‐expressing T cells in autoimmune‐prone mice

Systemic autoimmune diseases, such as systemic lupus erythematosus (SLE), are often characterized by a failure of self‐tolerance and result in an uncontrolled activation of B cells and effector T cells. Interleukin (IL)‐2 critically maintains homeostasis of regulatory T cells (T_reg) and effector T cells in the periphery. Previously, we identified the cAMP‐responsive element modulator α (CREMα) as a major factor responsible for decreased IL‐2 production in T cells from SLE patients. Additionally, using a transgenic mouse that specifically over‐expresses CREMα in T cells (CD2CREMαtg), we provided in‐vivo evidence that CREMα indeed suppresses IL‐2 production. To analyse the effects of CREMα in an autoimmune prone mouse model we introduced a Fas mutation in the CD2CREMαtg mice (FVB/Fas^–/–CD2CREMαtg). Overexpression of CREMα strongly accelerated the lymphadenopathy and splenomegaly in the FVB/Fas^–/– mice. This was accompanied by a massive expansion of double‐negative (DN) T cells, enhanced numbers of interferon (IFN)‐γ‐producing T cells and reduced percentages of T_regs. Treatment of FVB/Fas^–/–CD2CREMαtg mice with IL‐2 restored the percentage of T_regs and reversed increased IFN‐γ production, but did not affect the number of DNTs. Our data indicate that CREMα contributes to the failure of tolerance in SLE by favouring effector T cells and decreasing regulatory T cells, partially mediated by repression of IL‐2 in vivo .     

Regulatory T cells and minimal change nephropathy: in the midst of a complex network

Minimal change nephrosis (MCN) is an important cause of morbidity in children. In spite of successful therapies having been developed in the last three decades, most aspects related to pathogenesis still remain poorly defined. Evolution in basic immunology and results deriving from animal models of the disease suggest a complex interaction of factors and cells starting from activation of innate immunity and continuing with antigen presentation. Oxidants, CD80 and CD40/CD40L have probably a relevant role at the start. Studies in animal models and in human beings also suggest the possibility that the same molecules (i.e. CD80, CD40) are expressed by podocytes under inflammatory stimuli, representing a direct potential mechanism for proteinuria. B and T cells could play a relevant role this contest. Implication of B cells is suggested indirectly by studies utilizing anti‐CD20 monoclonal antibodies as the main therapy. The role of regulatory T cells (T_regs) is supported mainly by results in animal models of nephrotic syndrome (i.e. adriamycin, puromycin, lipopolysaccharide), showing a protective effect of direct T_reg infusion or stimulation by interleukin 2 (IL‐2). Limited studies have also shown reduced amounts of circulating T_regs in patients with active MCN cells. The route from bench to bedside would be reduced if results from animal models were confirmed in human pathology. The expansion of T_regs with recombinant IL‐2 and new anti‐CD20 monoclonal antibodies is the beginning. Blocking antigen‐presenting cells with cytotoxic T lymphocyte antigen (CTLA‐4)–Ig fusion molecules inhibiting CD80 and/or with blockers of CD40–CD40 ligand interaction represent potential new approaches. The hope is that evolution in therapies of MCN could fill a gap lasting 30 years.