T cells induce terminal differentiation of transformed B cells to mature plasma cell tumors

A Rare Case of Multple Myeloma (Mm) Presented With Pancytopaenia in A Patient of HIV - At Very Early Age

Non-hodgkin`s lymphoma (NHL) is the most common haematological malignancy which is seen in HIV infected patients. Among NHLs, immunoblastic lymphomas are most common and a majority of these are diffuse large B-cell lymphomas. Multiple myeloma is a disease of the elderly. It is extremely rare below 30 years of age. On the other hand, in HIV infected individuals, the average age of presentation with plasma cell disorders is 33 years, which is far younger than the average age of presentation in general population. The incidence of AIDS defining malignancies has declined markedly, whereas non-AIDS defining cancers are being increasingly diagnosed in patients with HIV infection during the HAART-era and they may be the presenting manifestations of AIDS. Multiple myeloma, however, usually is not a first presenting feature of AIDS. The usual clinical presentation of multiple myeloma is bone pain and pallor. Pancytopaenia is a rare presenting feature of multiple myeloma. Here, we are reporting a case of pancytopaenia which occurred in a 28-year-old, newly diagnosed, HIV-1 positive female, who with the help of bone marrow examination and further investigations, was subsequently diagnosed as multiple myeloma.

Evolving spectrum of HIV-associated nephropathy

BACKGROUND

The profile of renal pathology in HIV patients is undergoing significant changes in pattern in the HAART era, with the incidence of HIV-associated nephropathy (HIVAN) decreasing and the incidence of non-HIVAN lesions increasing.

CASE REPORTS

We describe 2 cases of HIV-infected patients diagnosed with diffuse infiltrative lymphocytosis syndrome (DILS) and coexistent multiple myeloma, an association that has heretofore been unreported. The cases involve a 23-year-old man and a 54-year-old man who presented with renal failure and proteinuria. Kidney biopsy in both revealed DILS and further evaluation revealed both to have multiple myeloma.

CONCLUSION

DILS is a late complication of AIDS that has become extremely rare in the United States during the HAART era. However, there are patients who present without an AIDS-defining illness or cancers. The development of multiple myeloma in the setting of HIV and DILS presents a novel, heretofore unreported association that may be important to recognize in HIV/AIDS patients with kidney failure.

Chemokine-dependent B cell-T cell interactions in chronic lymphocytic leukemia and multiple myeloma - targets for therapeutic intervention?

INTRODUCTION

Chemokines and their receptors play essential roles in the development, maintenance and proper functioning of the immune system. B cell-T cell interactions are modulated by chemokines. In B cell malignancies, these interactions may have tumor-promoting consequences.

AREAS COVERED

This review summarizes physiological B cell-T cell interactions and discusses their pathological role in the onset and progression of B cell malignancies with a special focus on chronic lymphocytic leukemia and multiple myeloma. Experimental data on chemokine-guided B cell-T cell actions in B cell malignancies from murine models as well as in vitro data are summarized and their potential as future therapeutic targets is critically discussed.

EXPERT OPINION

Direct or indirect targeting of chemokine receptors involved in localization and T-cell-dependent activation of B lymphocytes can provide strong synergisms with conventional or immunomodulatory therapies by disrupting the microenvironmental conditions necessary for survival and proliferation of malignant B lymphocytes. However, further knowledge of these interactions between B and T cells is needed.

Variations in suppressor molecule ctla-4 gene are related to susceptibility to multiple myeloma in a polish population

Various phenotype and functional T-cell abnormalities are observed in multiple myeloma (MM) patients. The aim of this study was to investigate the association between polymorphisms in the gene encoding cytotoxic T-lymphocyte antigen-4 (CTLA-4), a negative regulator of the T-lymphocyte immune response and susceptibility to multiple myeloma in a Polish population. Two hundred MM patients and 380 healthy subjects were genotyped for the following polymorphisms: CTLA-4c.49A>G, CTLA-4g.319C>T, CTLA-4g.*642AT(8_33), CT60 (CTLA-4g.*6230G>A), Jo31 (CTLA-4g.*10223G>T). Our study is the largest and most comprehensive evaluation to date of the association between genetic polymorphisms in the CTLA-4 molecule and multiple myeloma. It was found that CTLA-4c.49A>G[G], CT60[G], and Jo31[G] alleles were more frequently observed in MM patients than in controls (0.50 vs. 0.44, p = 0.03, 0.65 vs. 0.58, p = 0.04, and 0.63 vs. 0.57, p = 0.03, respectively). Moreover, the haplotype CTLA-4c.49A>G[G], CTLA-4g.319C>T[C], CTLA-4g.*642AT(8_33) [8], CT60[G], Jo31[G] including all susceptibility alleles increases the risk of MM about fourfold (OR: 3.79, 95%CI: 2.08–6.89, p = 0.00001). These findings indicate that genetic variations in the CTLA-4 gene play role in susceptibility to multiple myeloma and warrant further investigation through replication studies.

A case presenting with rapid renal damage caused by immunoglobulin D lambda-type multiple myeloma accompanied by granular lymphocyte proliferative disorder

A 69-year-old man was referred to our hospital for severe anemia. The atypical lymphocyte count, including granular lymphocytes, was 2,750/μL. Lymphocyte surface marker analysis showed CD3+, CD5+, CD16+, and CD56+ cells. Mixed T cell- and natural killer cell-type granular lymphocyte proliferative disorder (GLPD) was diagnosed. Because his serum creatinine levels deteriorated rapidly over the next 3 months, from 0.96 to 3.27 mg/dL, he was admitted to our hospital. The serum levels of immunoglobulins (Ig) other than IgD had decreased, and monoclonal protein was detected in the gamma-globulin region. Immunoelectrophoresis revealed IgD and lambda (λ) proteins in the serum and λ-type Bence-Jones protein in the urine. Renal biopsy examination revealed widespread tubular atrophy and interstitial fibrosis, and cast formation with λ protein deposits in tubular lumens, indicating cast nephropathy. These results indicated that the rapid renal damage was caused by IgD λ-type multiple myeloma accompanied by GLPD. The clinical course of GLPD is not usually aggressive and the findings of physical examinations are not significant. GLPD is usually associated with cytopenia (neutropenia or anemia), viral infections, collagen diseases, neoplasms such as malignant lymphoma, or chronic infections. To date, there are only 2 case reports of GLPD accompanied by multiple myeloma but without renal function or renal histological findings. When the clinical course of GLPD is aggressive and is accompanied with rapid renal damage, multiple myeloma should be considered as a complication.

Expansion of immunoglobulin autoreactive T-helper cells in multiple myeloma

Activation and expansion of T helper (Th) cells followed by regulation of activation are essential to the generation of immune responses while limiting concomitant autoreactivity. In order to characterize T cells reactive towards myeloma-derived monoclonal immunoglobulin (mIg), an autologous coculture assay for single-cell analysis of mIg-responding cells was developed. When cultured with dendritic cells loaded with mIg, CD4(+) Th cells from patients with progressing multiple myeloma (MM) showed a proliferative MHC class II-dependent response. CD8(+) T-cell reactivity and Th1 activation were consistently low or absent, and Th2 and regulatory cytokines were expressed. The presence of such non-Th1 CD4(+) T cells in peripheral blood was independent of treatment status, while the frequencies of responding cells varied between patients and reached the same order of magnitude as those measured for tetanus toxoid-specific Th memory cells. Furthermore, investigations of T-cell subpopulations indicated a possible regulatory role on the mIg responsiveness mediated by suppressive CD25(high)FOXP3(+)CD4(+) T cells. It is proposed from the present results that a predominant in vivo activation of non-Th1 mIg-reactive CD4(+) T cells constitute an Ig-dependent autoregulatory mechanism in human MM, with possible tumor growth supporting or permissive effects.

Selenium Deficiency Abrogates Inflammation-Dependent Plasma Cell Tumors in Mice

The role of the micronutrient, selenium, in human cancers associated with chronic inflammations and persistent infections is poorly understood. Peritoneal plasmacytomas (PCTs) in strain BALB/c (C), the premier experimental model of inflammation-dependent plasma cell transformation in mice, may afford an opportunity to gain additional insights into the significance of selenium in neoplastic development. Here, we report that selenium-depleted C mice (n = 32) maintained on a torula-based low-selenium diet (5-8 micro g of selenium/kg) were totally refractory to pristane induction of PCT. In contrast, 11 of 26 (42.3%) control mice maintained on a selenium adequate torula diet (300 micro g of selenium/kg) and 15 of 40 (37.5%) control mice fed standard Purina chow (440 micro g of selenium/kg) developed PCT by 275 days postpristane. Abrogation of PCT was caused in part by the striking inhibition of the formation of the inflammatory tissue in which PCT develop (pristane granuloma). This was associated with the reduced responsiveness of selenium-deficient inflammatory cells (monocytes and neutrophils) to chemoattractants, such as thioredoxin and chemokines. Selenium-deficient C mice exhibited little evidence of disturbed redox homeostasis and increased mutant frequency of a transgenic lacZ reporter gene in vivo. These findings implicate selenium, via the selenoproteins, in the promotion of inflammation-induced PCT and suggest that small drug inhibitors of selenoproteins might be useful for preventing human cancers linked with chronic inflammations and persistent infections.

Vigorous premalignancy-specific effector T cell response in the bone marrow of patients with monoclonal gammopathy

Most approaches targeting the immune system against tumors have focused on patients with established tumors. However, whether the immune system can recognize preneoplastic stages of human cancer is not known. Here we show that patients with preneoplastic gammopathy mount a vigorous T cell response to autologous premalignant cells. This preneoplasia-specific CD4⁺ and CD8⁺ T cell response is detected in freshly isolated T cells from the BM. T cells from myeloma marrow lack this tumor-specific rapid effector function. These data provide direct evidence for tumor specific immune recognition in human preneoplasia and suggest a possible role for the immune system in influencing the early growth of transformed cells, long before the development of clinical cancer.

Immunotherapy in multiple myeloma: current strategies and future prospects

Multiple myeloma is still a fatal disease. Despite advances in high-dose chemotherapy supported by autologous transplantations, relapse of the underlying disease remains the primary cause of treatment failure. Strategies for post-transplantation immunomodulation would be desirable for eradication of remaining tumor cells. Toward this end, immunotherapy aimed at inducing myeloma-specific immunity in patients has been exploited. Idiotype protein, secreted by myeloma cells, has been the main target for immunotherapy as it is the best-defined, tumor-specific antigen. The focus of this review article is the use of idiotype as a form of protein antigen to immunize patients, to load dendritic cells, or as part of DNA vaccines. Various strategies of immunotherapy and the outcome of clinical trials are also discussed.

Depletion of CD4(+) T cells aggravates glomerular and interstitial injury in murine adriamycin nephropathy

BACKGROUND

CD4(+) T cells play an important role in various types of immunologic renal disease, including lupus nephritis, IgA nephropathy, and crescentic glomerulonephritis. CD4(+) T cells are also major infiltrating lymphocytes in chronic tubulointerstitial inflammation associated with nonimmunological renal diseases. We suspected that CD4(+) T cells might contribute to disease progression and loss of renal function in chronic proteinuric renal disease (CPRD). To investigate this possibility, the effect of monoclonal antibody against CD4(+) lymphocytes (anti-CD4) was studied in a murine model (adriamycin nephropathy) of CPRD.

METHODS

Adriamycin nephropathy was produced in male BALB/c mice by a single intravenous injection of adriamycin (11 mg/kg). Anti-CD4 was given by intraperitoneal injection following the development of proteinuria at days 5, 6, 7, 21, and 37 after adriamycin. After six weeks, renal function and histology were studied by histomorphometry, immunohistochemistry, and flow cytometry.

RESULTS

Flow cytometric analysis showed a marked decrease in the number of CD4(+) T cells in blood and spleen of the antibody-treated animals (N = 7, P < 0.01). Adriamycin plus CD4(+) depletion mice had significantly greater mesangial expansion, glomerular sclerosis, and interstitial expansion than the mice on adriamycin alone. Interstitial infiltration with macrophages and CD8(+) cells was significantly increased in adriamycin plus CD4(+) depletion mice. Creatinine clearance (17.5 +/- 0.54 vs. 29.2 +/- 0.89 microL/min, P < 0.001) was significantly worse in the adriamycin plus CD4(+) depletion mice than in adriamycin alone mice and correlated with histologic change in glomeruli and interstitium.

CONCLUSIONS

Depletion of CD4(+) T cells promotes glomerular and interstitial injury in mice with established adriamycin nephropathy. These findings suggest that CD4(+) T cells have a protective role against the progression of adriamycin nephropathy.

Multiple myeloma and human immunodeficiency virus-1 (HIV-1) infection

Multiple myeloma (MM) in three human immunodeficiency virus (HIV)-infected patients is reported. HIV infection predisposes to the development of high-grade B-cell lymphomas, but few cases of plasma cell tumours in association with HIV have been reported. The coincidence of HIV infection and neoplasia highlights the distinct roles of immunodeficiency and infection with herpesviridae, including HIV itself, in the pathogenesis of HIV-related tumours. In addition, a number of cytokines (e.g., interleukin-6 [IL-6]) and angiogenic factors (e.g., vascular endothelial growth factor [VEGF] and basic fibroblastic growth factor [bFGF]) may play a role in the initiation, maintenance, and progression of multiple myeloma (MM). Infection was the first clinical consideration to the cause of the illness in two of our HIV-seropositive patients. The diagnosis of MM may be difficult in patients with advanced HIV infection as they often have renal failure, bone marrow plasmacytosis, repeated infections, and polyclonal hypergammaglobulinaemia, due to HIV infection itself, opportunistic pathogens, and/or medication.

Cytotoxic T-lymphocyte antigen-4 microsatellite polymorphism is associated with multiple myeloma

Multiple myeloma (MM) is a B-lineage malignancy with unknown aetiology. It has been considered that predisposing genetic factors might be implicated in the disease. In this study, the microsatellite polymorphism in the exon 3 of the cytotoxic T-lymphocyte antigen-4 (CTLA-4) gene was analysed in patients with MM and monoclonal gammopathy of undetermined significance (MGUS), together with ethnically matched healthy controls. The results showed that frequencies of the genotype 86/86 and of the allele 86 were significantly decreased in MM and MGUS compared with matched healthy controls, indicating that the CTLA-4 microsatellite polymorphism might represent a susceptibility locus for MM and MGUS.

Loss of PTEN expression leading to high Akt activation in human multiple myelomas

Mouse plasma cell tumor (PCT) and human multiple myeloma (MM) are terminal B-cell malignancies sharing many similarities. Our recent work demonstrated that activation of the insulin-like growth factor receptor (IGF-IR)/insulin receptor substrate (IRS)/phosphatidylinositol 3′ kinase (PI 3′K) pathway was evident in the tumor lines derived from both species. Although PI 3′K activity was higher in mouse tumor lines than that in human tumors, activation of Akt serine/threonine kinase was markedly lower in mouse lines. This discrepancy prompted us to test the status of PTEN tumor suppressor gene, as it has been shown to be a negative regulator of PI 3′K activity. Although all the mouse lines expressed intact PTEN, 2 of the 4 human lines (Δ47 and OPM2) possessing the highest Akt activity lost PTEN expression. Sequencing analysis demonstrated that the PTEN gene contains a deletion spacing from exon 3 to exon 5 or 6 in the Δ47 line and from exon 3 to 7 in the OPM2 line. Restoration of PTEN expression suppressed IGF-I–induced Akt activity, suggesting that loss of PTEN is responsible for uncontrolled Akt activity in these 2 lines. Despite the expression of PTEN with the concomitant low Akt activity in all mouse PCT lines, their p70S6K activities were generally higher than those in 3 human MM lines, arguing for specific negative regulation of Akt, but not p70S6K by PTEN. These results suggest that p70S6K and Akt may be differentially used by the plasma cell tumors derived from mice and humans, respectively.

Loss of PTEN expression leading to high Akt activation in human multiple myelomas

Mouse plasma cell tumor (PCT) and human multiple myeloma (MM) are terminal B-cell malignancies sharing many similarities. Our recent work demonstrated that activation of the insulin-like growth factor receptor (IGF-IR)/insulin receptor substrate (IRS)/phosphatidylinositol 3′ kinase (PI 3′K) pathway was evident in the tumor lines derived from both species. Although PI 3′K activity was higher in mouse tumor lines than that in human tumors, activation of Akt serine/threonine kinase was markedly lower in mouse lines. This discrepancy prompted us to test the status of PTEN tumor suppressor gene, as it has been shown to be a negative regulator of PI 3′K activity. Although all the mouse lines expressed intact PTEN, 2 of the 4 human lines (Δ47 and OPM2) possessing the highest Akt activity lost PTEN expression. Sequencing analysis demonstrated that the PTEN gene contains a deletion spacing from exon 3 to exon 5 or 6 in the Δ47 line and from exon 3 to 7 in the OPM2 line. Restoration of PTEN expression suppressed IGF-I–induced Akt activity, suggesting that loss of PTEN is responsible for uncontrolled Akt activity in these 2 lines. Despite the expression of PTEN with the concomitant low Akt activity in all mouse PCT lines, their p70S6K activities were generally higher than those in 3 human MM lines, arguing for specific negative regulation of Akt, but not p70S6K by PTEN. These results suggest that p70S6K and Akt may be differentially used by the plasma cell tumors derived from mice and humans, respectively.

Neoplasia of plasma cells with atypical presentation and infection by the human immunodeficiency virus. A presentation of two cases

Neoplasia of plasma cells acquires special clinical characteristics in patients infected by human immunodeficiency virus (HIV). These patients are much younger at the time of diagnosis, and when they are compared with the general population they show an atypical clinical evolution, with a greater frequency of solitary plasmacytomas, less evidence of a monoclonal plasmatic component, or greater aggressiveness of the neoplastic process. This paper provides the most significant data on two patients infected by HIV and diagnosed for plasma cell neoplasia. Recent pathogenetic hypotheses for plasma cell neoplasias that include immune alterations, chronic viral infections, and hyperexpression of cytokines exist in patients infected by HIV, and this could suggest that this type of neoplasia is another malignant haematological process associated with AIDS.

Roles of STAT3 in mediating the cell growth, differentiation and survival signals relayed through the IL-6 family of cytokine receptors

Members of the IL-6 cytokine family are involved in a variety of biological responses, including the immune response, inflammation, hematopoiesis, and oncogenesis by regulating cell growth, survival, and differentiation. These cytokines use gp130 as a common receptor subunit. The binding of ligand to gp130 activates the JAK/STAT signal transduction pathway, where STAT3 plays a central role in transmitting the signals from the membrane to the nucleus. STAT3 is essential for gp130-mediated cell survival and G1 to S cell-cycle-transition signals. Both c-myc and pim have been identified as target genes of STAT3 and together can compensate for STAT3 in cell survival and cell-cycle transition. STAT3 is also required for gp130-mediated maintenance of the pluripotential state of proliferating embryonic stem cells and for the gp130-induced macrophage differentiation of M1 cells. Furthermore, STAT3 regulates cell movement, such as leukocyte, epidermal cell, and keratinocyte migration. STAT3 also appears to regulate B cell differentiation into antibody-forming plasma cells. Since the IL-6/gp130/STAT3 signaling pathway is involved in both B cell growth and differentiation into plasma cells it is likely to play a central role in the generation of plasma cell neoplasias. Oncogene (2000).

BLyS: member of the tumor necrosis factor family and B lymphocyte stimulator

The tumor necrosis factor (TNF) superfamily of cytokines includes both soluble and membrane-bound proteins that regulate immune responses. A member of the human TNF family, BLyS (B lymphocyte stimulator), was identified that induced B cell proliferation and immunoglobulin secretion. BLyS expression on human monocytes could be up-regulated by interferon-gamma. Soluble BLyS functioned as a potent B cell growth factor in costimulation assays. Administration of soluble recombinant BLyS to mice disrupted splenic B and T cell zones and resulted in elevated serum immunoglobulin concentrations. The B cell tropism of BLyS is consistent with its receptor expression on B-lineage cells. The biological profile of BLyS suggests it is involved in monocyte-driven B cell activation.

Assessment of all-trans retinoic acid (ATRA) efficacy as a single agent in primary lymphoid neoplasia

All-trans retinoic acid (ATRA) is currently widely used in the therapy of acute promyelocytic leukemia and is being tested in vitro and in vivo on several other malignancies. Previously ATRA has been shown to inhibit the growth in vitro, of established human myeloma cell lines as well as cultured primary myeloma cells from patients. ATRA acts by down-regulating IL-6-receptor-alpha or gp130 on the surface of the myeloma cells. However, despite its in vitro effects on myeloma cells, ATRA therapy on advanced stage multiple myeloma (MM) patients has so far largely been ineffective. In current studies, we have assessed the efficacy of ATRA therapy against primary murine plasma cell tumors, which are an animal model for human MM. These tumors are induced at about 50% incidence in pristane-primed BALB/c mice by injection of v-raf/v-myc- containing retroviruses and are IL-6 dependent. Using this animal model, we assessed the effect of ATRA as a therapeutic agent against primary tumors at two early time points in disease development. ATRA was administered in liposomal vesicles (ATRAGEN), since liposomal-ATRA has been shown to circumvent clearance mechanisms by hepatic microsomes, which normally occur with free ATRA. In addition, ATRAGEN was previously shown to be less toxic in mice than free ATRA. ATRAGEN was administered beginning on day 25 or day 45 after virus injection and continued twice weekly for 8-11 weeks. ATRAGEN administration begun at either time point did not alter the incidence or the latency of plasma cell tumors compared with control animals. These results suggest that ATRA may not be an effective sole therapy against early MM.

bcl2 and v-abl oncogenes cooperate to immortalize murine B cells that secrete antigen specific antibodies

In this manuscript, a general strategy was designed and used to rapidly test whether any combination(s) of p53, v-abl, bcl2 and ras oncogenes could act cooperatively to immortalize B cells. Here we report that only the combination of v-abl and bcl2 was successful. Splenic B cells from beta galactosidase-immunized mice were stimulated in vitro with lipopolysaccharide and dextran sulphate for 48 h and co-infected with ecotropic A-MuLV (v-abl) and amphotropic pZip-bcl2 (human bcl2) viruses. When inoculated i.p. into naive pristane-primed mice, these B cells generated mesenteric lymphadenopathy, intraperitoneal lymph nodules and ascites in 100% (8/8) of the mice within 36-53 days. The ascites fluid contained 69.5-122 microg/ml IgG and 2.5-13 microg/ml IgM against the immunogen. The ascites cells were passed intraperitoneally up to three times. In all passages, ascites tumors were generated, and the ascites fluid contained beta galactosidase-specific IgG and IgM, indicating that some immunoglobulin secreting B cells had been immortalized. Neither ascites nor tumors were produced when B cells infected with only one of the viruses was injected into the mice. The presence of each oncogene in ascites cells was verified by immunohistochemistry or RT-PCR. This study provides evidence for the cooperativity of an unexpected pair of oncogenes in B cell immortalization.

Interleukin-2-mediated modulation of plasma cell tumor growth in a model of multiple myeloma

A number of studies have demonstrated that inoculation of certain types of cancer cells engineered for expression of the interleukin-2 (IL-2) gene results in reduced tumorigenicity and/or protection from subsequent challenge with a tumorigenic dose of wild-type cells. In the current studies, we have employed murine plasma cell tumors to examine IL-2-mediated tumor rejection as a possible model for therapeutic approaches to human myeloma or plasma cell leukemia. Two murine plasma cell tumor lines, S107 and X24, were infected with a retroviral vector expressing the human IL-2 gene, and the antitumor potential of IL-2-expressing infectants was characterized in syngeneic BALB/c and BALB/c nu/nu mice. Results demonstrate that tumorigenicity of both lines correlates inversely with the amount of IL-2 produced by the tumor cells. However, there are clear differences between the two lines in terms of reduced tumorigenicity and the ability to protect against co-injected parental tumor cells that appear unrelated to IL-2 levels. More importantly, intravenous immunization of animals with irradiated, IL-2 secreting cells from either line leads to significant protection from challenge with highly metastatic parental cells. These results suggest that such an approach may warrant consideration in the treatment of human plasma cell dyscrasias.

Defective development of pristane-oil-induced plasmacytomas in interleukin-6-deficient BALB/c mice

Interleukin (IL)-6 is known to be an essential growth factor for myeloma cells, both in vitro and in vivo. In mice, IL-6 is required for development of B cell tumors upon infection with a retrovirus expressing the myc/raf oncogenes. In the present study, we used the pristane-oil-induced plasmacytoma model, which more closely mimics tumor transformation and progression in human multiple myeloma. Also using this system, we found that IL-6-deficient BALB/c mice are protected against tumor development. Although the pristane-induced inflammatory reaction was less pronounced in IL-6-deficient mice versus their wild-type littermates, both B cell differentiation and plasma cell formation took place, and even morphological evidence of plasma cell transformation was detected, albeit at a low frequency. However, in the absence of IL-6, there were never signs of uncontrolled proliferation of either normal B lymphocytes or tumor cells, suggesting that the role of IL-6 in murine plasmacytoma and possibly also in human multiple myeloma is to ensure abnormal survival and proliferation of previously transformed tumor cells and therefore tumor development and progression.

Immunoregulatory mechanisms in multiple myeloma

This review presents current experimental data regarding immunologic changes associated with multiple myeloma (Table 1). It is becoming increasingly clear that some of the immunologic changes are host responses to the malignant plasma cell clone and monoclonal immunoglobulin. In the last 2 to 3 years an anti-idiotypic response has been clearly documented, and cells expressing CD16 and soluble CD16 have been identified as modulators of myeloma cell growth and differentiation. Abnormalities in B- and T-cell differentiation have been observed, most consistently the deficiency of T4 helper cells. Differences in the immunologic changes point to the provocative hypothesis that, in MGUS and the initial stages of myeloma, immunologic responses play an important role in controlling proliferation of the malignant clone, and at some point the system is overwhelmed or fails, leading to an overt or more aggressive disease. The quest is to understand the genesis of the autoregulatory circuits operative in myeloma. Novel strategies for immunotherapy in management of myeloma will arise through improved understanding of host immune response and its cause-and-effect relationship with myeloma cell growth.

Autoimmunity associated with TGF-beta1-deficiency in mice is dependent on MHC class II antigen expression

The progressive inflammatory process found in transforming growth factor beta1 (TGF-beta1)-deficient mice is associated with several manifestations of autoimmunity, including circulating antibodies to nuclear antigens, immune complex deposition, and increased expression of both class I and class II major histocompatibility complex (MHC) antigens. The contribution of MHC class II antigens to the genesis of this phenotype has been determined by crossing the TGF-beta1-null [TGF-beta1(-/-)] genotype into the MHC class II-deficient [MHC-II(-/-)] background. Mice homozygous for both the TGF-beta1 null allele and the class II null allele [TGF-beta1(-/-);MHC-II(-/-)] are without evidence of inflammatory infiltrates, circulating autoantibodies, or glomerular immune complex deposits. Instead, these animals exhibit extensive extramedullary hematopoiesis with progressive splenomegaly and adenopathy, surviving only slightly longer than TGF-beta1(-/-);MHC-II(+/+) mice. The role of CD4+ T cells, which are also absent in MHC class II-deficient mice, is directly demonstrated through the administration of anti-CD4 monoclonal antibodies in class II-positive, TGF-beta1(-/-) mice. The observed reduction in inflammation and improved survival emphasize the significance of CD4+ cells in the pathogenesis of the autoimmune process and suggest that the additional absence of class II antigens in TGF-beta1(-/-);MHC-II(-/-) mice may contribute to their extreme myeloid metaplasia. Thus, MHC class II antigens are essential for the expression of autoimmunity in TGF-beta1-deficient mice, and normally may cooperate with TGF-beta1 to regulate hematopoiesis.

Distinct tumorigenic potential of abl and raf in B cell neoplasia: abl activates the IL-6 signaling pathway

The development of murine plasma cell tumors induced by raf/myc containing retroviruses is facilitated by T cells and completely dependent on IL-6. To determine whether kinases with differing specificities reflect alternative biochemical pathways in B cell tumorigenesis, we have employed an abl/myc containing retrovirus to assess neoplastic development. In contrast with raf/myc, abl/myc disease is T cell and IL-6 independent. An examination of the IL-6 signal transduction pathway reveals that this pathway, as defined by activation of Stat3, is inducible by IL-6 in raf/myc tumors but constitutively activated in abl/myc tumors. These findings provide a mechanism for the derivation of cytokine-independent plasma cell tumors and suggest that both IL-6-dependent and independent tumors may arise in vivo depending on the particular mutational events incurred during tumorigenesis.

Idiotype-specific T cells in multiple myeloma: targets for an immunotherapeutic intervention?

In this paper, the results of some recent studies on idiotype-specific T cells in human multiple myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS) are discussed. By using different in vitro measurements such as 3H-thymidine incorporation and ELI-SPOT assay, idiotype-specific T cells have been demonstrated in most of MM and MGUS patients. Based on the cytokine-secretion profiles, idiotype-specific T cells were found to comprise both Th1 and Th2 cells. A Th1 type immunity was found preferentially in indolent disease and a Th2-like response predominated in advanced MM, suggesting a specific T-cell regulation of the tumor B-cell clone. The mode of T-cell recognition of id determinants on M-components has been studied. We found that idiotype-specific T cells recognized processed id determinants presented by MHC class II (HLA-DR) molecules on APC. B cells were much more efficient APC than monocytes. With the aim to induce or to amplify an idiotype-specific T-cell response, we have immunized MM patients with the autologous M-component precipitated in aluminum. Three out of the five patients showed an induction of specific cellular and humoral immunity. Nevertheless, the role for such immunity in controlling the tumor clone remains to be established.

Interleukin 6 is essential for in vivo development of B lineage neoplasms

Interleukin (IL) 6 has been suggested to be the major cytokine responsible for proliferation of neoplastic plasma cells in both human myeloma and mouse plasmacytoma. Much of the evidence supporting this suggestion is derived from in vitro studies in which the survival or proliferation of some plasma cell tumors has been found to be IL-6 dependent. However, it remains unclear whether this dependency is the consequence of in vivo or in vitro selective pressures that preferentially expand IL-6-responsive tumor cells, or whether it reflects a critical in vivo role for IL-6 in plasma cell neoplasia. To address this question, we have attempted to induce plasma cell tumors in normal mice and in IL-6-deficient mice generated by introduction of a germline-encoded null mutation in the IL-6 gene. The results demonstrate that mice homozygous (+/+) or heterozygous (+/-) for the wild-type IL-6 allele yield the expected incidences of plasma cell tumors. In contrast, mice homozygous for the IL-6-null allele (-/-) are completely resistant to plasma cell tumor development. These studies define the essential role of IL-6 in the development of B lineage tumors in vivo and provide experimental support for continued efforts to modulate this cytokine in the treatment of appropriate human B cell malignancies.