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We hypothesized that combining adoptively transferred autologous T cells with a cancer vaccine strategy would enhance therapeutic efficacy by adding antimyeloma idiotype (Id)–keyhole limpet hemocyanin (KLH) vaccine to vaccine-specific costimulated T cells. In this randomized phase 2 trial, patients received either control (KLH only) or Id-KLH vaccine, autologous transplantation, vaccine-specific costimulated T cells expanded ex vivo, and 2 booster doses of assigned vaccine. In 36 patients (KLH, n = 20; Id-KLH, n = 16), no dose-limiting toxicity was seen. At last evaluation, 6 (30%) and 8 patients (50%) had achieved complete remission in KLH-only and Id-KLH arms, respectively (P = .22), and no difference in 3-year progression-free survival was observed (59% and 56%, respectively; P = .32). In a 594 Nanostring nCounter gene panel analyzed for immune reconstitution (IR), compared with patients receiving KLH only, there was a greater change in IR genes in T cells in those receiving Id-KLH relative to baseline. Specifically, upregulation of genes associated with activation, effector function induction, and memory CD8+ T-cell generation after Id-KLH but not after KLH control vaccination was observed. Similarly, in responding patients across both arms, upregulation of genes associated with T-cell activation was seen. At baseline, all patients had greater expression of CD8+ T-cell exhaustion markers. These changes were associated with functional Id-specific immune responses in a subset of patients receiving Id-KLH. In conclusion, in this combination immunotherapy approach, we observed significantly more robust IR in CD4+ and CD8+ T cells in the Id-KLH arm, supporting further investigation of vaccine and adoptive immunotherapy strategies. This trial was registered at www.clinicaltrials.gov as #NCT01426828.

A promising therapy for patients with B-cell lymphoma is based on vaccination with idiotype monoclonal antibodies (mAbs). Since idiotypes are different in each tumor, a personalized vaccine has to be produced for each patient. Expression of immunoglobulins with appropriate post-translational modifications for human use often requires the use of stable mammalian cells that can be scaled-up to reach the desired level of production. We have used a noncytopathic self-amplifying RNA vector derived from Semliki Forest virus (ncSFV) to generate BHK cell lines expressing murine follicular lymphoma-derived idiotype A20 mAb. ncSFV/BHK cell lines expressed approximately 2 mg/L/24 h of A20 mAb with proper quaternary structure and a glycosylation pattern similar to that of A20 mAb produced by hybridoma cells. A20 mAb purified from the supernatant of a ncSFV cell line, or from the hybridoma, was conjugated to keyhole limpet hemocyanin and used to immunize Balb/c mice by administration of four weekly doses of 25 µg of mAb. Both idiotype mAbs were able to induce a similar antitumor protection and longer survival compared to non-immunized mice. These results indicate that the ncSFV RNA vector could represent a quick and efficient system to produce patient-specific idiotypes with potential application as lymphoma vaccines.

Immunoglobulin G can inhibit antibody response. The mechanism of immunosuppression by immunoglobulins remains unknown. Recently, we found a new factor of immunoregulation referred to as regulatory rheumatoid factor (regRF). RegRF prevents autoimmunity and reduces experimental autoimmune reactions. RegRF comprises a population of anti-idiotypic antibodies that have a unique paratope specific to the antigen-binding sites of the antibodies, and a shared paratope specific to neoepitopes of IgG Fc fragments. Given the specificity of regRF, we can anticipate that IgG would be able to induce regRF production, and consequently that the immunosuppressive effect of IgG may be mediated by regRF. We found that IgG induces regRF production in a culture of B lymphocytes obtained from the red bone marrow of intact rats. IgG does not expose neoepitopes recognized by the shared paratope of regRF, and does not acquire them in culture. Therefore, the stimulation of regRF production induced by IgG is not a result of the interaction between the shared paratope of regRF and the neoepitopes of IgG. Fc fragments of IgG are unable to stimulate regRF production. Fab fragments inhibit spontaneous regRF production. F(ab´)

To this day, multiple myeloma remains an incurable cancer. For many patients, recurrence is unavoidably a result of lacking treatment options in the minimal residual disease stage. This is due to residual and treatment-resistant myeloma cells that can cause disease relapse. However, patient-specific membrane-expressed paraproteins could hold the key to target these residual cells responsible for disease recurrence. Here, we describe the therapeutic potential of radiolabeled, anti-idiotypic camelid single-domain antibody fragments (sdAbs) as tumor-restrictive vehicles against a membrane-bound paraprotein in the syngeneic mouse 5T33 myeloma model and analogously assess the feasibility of sdAb-based personalized medicine for patients with multiple myeloma. Llamas were immunized using extracts containing paraprotein from either murine or human sera, and selective sdAbs were retrieved using competitive phage display selections of immune libraries. An anti-5T33 idiotype sdAb was selected for targeted radionuclide therapy with the β−-particle emitter 177Lu and the α-particle emitter 225Ac. sdAb-based radionuclide therapy in syngeneic mice with a low 5T33 myeloma lesion load significantly delayed tumor progression. In five of seven patients with newly diagnosed myeloma, membrane expression of the paraprotein was confirmed. Starting from serum-isolated paraprotein, for two of three selected patients anti-idiotype sdAbs were successfully generated.

Anti-idiotypic antibodies (Ab2), according to the network theory of Jerne, are second-generation immunoglobulins that are produced against the idiotype of an antibody to a specific antigen. Despite the large number of works devoted to the study of the properties of these proteins, their role in the regulation of the immune system is not fully known. It may consist in maintaining or blocking a minimal immune response to the antigen. The study of Ab2 is of great practical and scientific importance. The special properties of Ab2, namely, the ability to partially reproduce the structure of the primary antigen and, upon immunization, induce the appearance of tertiary antibodies, which, like first-generation antibodies, can bind to the antigen, have found application in the development of Ab2-based vaccines, in particular, for the treatment of tumors. In view of the presence of a number of limitations on research related to psychoactive substances, the development of Ab2- based vaccines against drug addiction also seems promising. To example, anti-idiotypic antibodies obtained for this purpose possessing a cocaine-like structure are described in the literature. In this work, murine monoclonal anti-idiotypic antibodies (mAb2) mimicking the structure of various morphine derivatives were obtained. Rabbit polyclonal antibodies to the 6-hemisuccinyl derivative of morphine conjugated with bovine serum albumin isolated by affinity chromatography were used as primary antibodies for immunization. Four hybridoma clones were obtained as a result of the fusion of immunized mice lymphocytes with mouse Sp2/0 mouse myeloma cells by the Milstein-Köhler method. After growth in animals, mAb2 produced by hybridoma cells were affinity purified. We investigated the physicochemical and antigenic properties of the isolated antibodies. It was shown that the obtained mAb2 differ in immunological specificity, competing in different degree with morphine derivatives for binding to first-generation antibodies. We tested the possibility of using the obtained mAb2 as antigen analogues in the solid-phase enzyme-linked immunosorbent assay to determine the titer of primary antibodies against morphine in the blood serum of laboratory animals immunized with morphine derivatives. Based on the obtained anti-idiotypic antibodies, it is proposed to develop test systems to determine the serum opiate-specific antibodies in people after specific vaccination for therapeutic or prophylactic purposes to avoid the use of drugs as antigens immobilized on the solid phase in the analysis.

The idiotype network is experimentally modified to provide protective immunity against various microbial pathogens. Both internal and non-internal image-idiotype antibodies can trigger specific immune responses to antigens. The current outbreak of Severe Acute Respiratory Syndrome 2 (SARS-2) has provided a great opportunity to take advantage of idiotype / anti-idiotype antibodies as a protective regimen when no approved vaccine is available on earth. The current review identifies successful applications of idiotype/ anti-idiotype antibodies in various viral diseases and highlights their importance in COVID-19 pandemics. In the absence of vaccines and targeted therapies, polyclonal idiotype/ anti-idiotype antibodies against the viral structure may be a potential approach to the prevention and treatment of COVID-19 patients.

DNase1L3 deficiency is an inborn error of immunity that causes monogenic systemic lupus erythematosus (SLE) in humans. Here, we identified that one third of patients with sporadic SLE have antibodies to DNase1L3. Like DNase1L3 deficiency, we found that patients with anti-DNase1L3 antibodies have features associated with immune pathways activated by immunogenic self-DNA, including elevated antibodies to dsDNA and prominent expression of the interferon and myeloid/neutrophil signatures. Interestingly, 40-80% of anti-DNase1L3 antibodies in SLE serum contain the 9G4 idiotype, which is encoded by the autoreactive heavy-chain gene segment VH4-34. Sequence and functional analysis of four anti-DNase1L3 monoclonal antibodies generated from SLE patients experiencing disease-associated flares showed that these antibodies were derived from self-reactive 9G4+ switched memory B cells. These antibodies are highly enriched in somatic hypermutations, indicating that they originated from antigen-experienced cells, and have neutralizing activity against DNase1L3. Together, the data demonstrate that autoantibodies to DNase1L3 phenocopy pathogenic mechanisms associated with DNase1L3 deficiency. Moreover, the finding that autoreactive B cells bearing the 9G4 idiotype produce dominant serum autoantibodies, including antibodies to DNase1L3, underscores VH4-34+ B cells as sensible therapeutic targets for specific depletion of pathogenic B cells in SLE.

Natalizumab (NZM), a humanized monoclonal IgG4 antibody to α4 integrins, is used to treat patients with relapsing-remitting multiple sclerosis (MS)1,2, but in about 6% of the cases persistent neutralizing anti-drug antibodies (ADAs) are induced leading to therapy discontinuation3,4. To understand the basis of the ADA response and the mechanism of ADA-mediated neutralization, we performed an in-depth analysis of the B and T cell responses in two patients. By characterizing a large panel of NZM-specific monoclonal antibodies, we found that, in both patients, the response was polyclonal and targeted different epitopes of the NZM idiotype. The neutralizing activity was acquired through somatic mutations and correlated with a slow dissociation rate, a finding that was supported by structural data. Interestingly, in both patients, the analysis of the CD4+ T cell response, combined with mass spectrometry-based peptidomics, revealed a single immunodominant T cell epitope spanning the FR2-CDR2 region of the NZM light chain. Moreover, a CDR2-modified version of NZM was not recognized by T cells, while retaining binding to α4 integrins. Collectively, our integrated analysis identifies the basis of T-B collaboration that leads to ADA-mediated therapeutic resistance and delineates an approach to design novel deimmunized antibodies for autoimmune disease and cancer treatment. An analysis of T cell specificities sufficient to sustain a neutralizing anti-drug antibody response offers a potential approach for enhancing the clinical efficacy of a therapeutic humanized antibody.

The PubMed data set was scanned with the title and abstract term "Idiotype" followed by secondary searches with "Vaccine" and "Clinical trial." The retrieved references were analyzed from the period before and after hybridoma technology (1975). In 1963, Oudin and Kunkel discovered that antibodies against antibodies can be raised to identify determinants unique to an antibody termed idiotype or individual antigenic determinant. Two laboratories reported that anti-idiotypic antibodies can suppress specific antibody responses in mice. In 1974, Jerne proposed a network of idiotypes and anti-idiotypes and the functionality of the idiotype network was confirmed. This prompted the proposal of a symmetrical regulatory immune response. By 1989, the concept and the functional parameters of the immune idiotype network were established in the prehybridoma period. It was not until 1981 that monoclonal anti-idiotypic antibodies were used as tools to study the expression of idiotypic determinants on antibodies and to categorize functional properties in the immune network as network antigens in 1989. Hybridoma-generated monoclonal anti-idiotypic antibodies provided the tools to precisely identify different idiotypic regions on antibodies and test these as targets to induce network cascades. The initial distinction of Ab2s as alpha and beta were expanded to include gamma and delta. The initial concept of Ab2beta being an antigen internal image, used as vaccine, was challenged showing that targeting all idiotopes on B cell receptors can induce specific antibodies. After the discovery of the hybridoma technology a wave of idiotype topic publications occurred, that declined by 2015. In 1985, in this wave of reports on anti-idiotypes, their importance to vaccines dominated. These vaccines targeted in animal models parasite, bacterial, and viral diseases, and cancer. The reported data indicated a therapeutic response in inbred mice. The issue of idiotype matching between mouse haplotypes of vaccine origin and treated mice were raised. In 1995, the human clinical trials in different cancers using anti-Id vaccines were reported. Only one such vaccine received conditional approval in Argentina and Cuba, whereas the other trials failed in phase II and III. The reasons for this failure were subsequently discussed. Although the use of the Milstein and Kohler hybridoma technology and subsequently alternative methods to produce monoclonal animal and human antibodies created a new class of drugs, commonly referred as "Biological," it failed on the promise therapeutic of anti-Id vaccines.

Antibody formation to human(ized) therapeutic antibodies in humans is highly skewed toward anti-idiotype responses, probably because the idiotype is the only ‘foreign’ part of the antibody molecule. Here, we analyzed antibody responses to F(ab’)2 fragments of a panel of 17 human(ized) therapeutic antibodies in rabbits. Homology between the rabbit germline and the human(ized) antibodies is moderate not only for the variable domains (both the complementarity-determining regions and the framework regions), but also for the constant domains (66% or less). Nevertheless, we observed a highly skewed anti-idiotype response in all cases, with up to >90% of the antibodies directed toward the idiotype. These results indicate that the idiotype may be inherently immunodominant. We used these biased responses to raise monoclonal rabbit anti-idiotype antibodies against secukinumab, ustekinumab, reslizumab, mepolizumab, palivizumab, and dupilumab and demonstrate the potential to develop sensitive pharmacokinetic assays with these antibodies.

Natural antibodies (NAbs) are important regulators of tissue homeostasis and inflammation and are thought to have diverse protective roles in a variety of pathological states. E06 is a T15 idiotype IgM NAb exclusively produced by B-1 cells, which recognizes the phosphocholine (PC) head group in oxidized phospholipids on the surface of apoptotic cells and in oxidized LDL (OxLDL), and the PC present on the cell wall of Streptococcus pneumoniae. Here we report that titers of the E06 NAb are selectively increased several-fold in Cd1d-deficient mice, whereas total IgM and IgM antibodies recognizing other oxidation specific epitopes such as in malondialdehyde-modified LDL (MDA-LDL) and OxLDL were not increased. The high titers of E06 in Cd1d-deficient mice are not due to a global increase in IgM-secreting B-1 cells, but they are specifically due to an expansion of E06-secreting splenic B-1 cells. Thus, CD1d-mediated regulation appeared to be suppressive in nature and specific for E06 IgM-secreting cells. The CD1d-mediated regulation of the E06 NAb generation is a novel mechanism that regulates the production of this specific oxidation epitope recognizing NAb.

Introduction. Anti-CD19 chimeric antigen receptor T cells (CART19, CTL019) have led to impressive clinical responses in relapsing or refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL). With the likely imminent approval of CTL019 for patients with B-ALL, increasing numbers of patients will be exposed to this therapy. Last year we reported a rare case of a single patient who relapsed with CD19-negative, CAR19-expressing leukemia, likely due to inadvertent transduction of a leukemic cell with the CAR19 lentivirus during CTL019 manufacturing (Lacey SF, ASH, 2016 #281). The high expression of the CAR in leukemic cells and its absence from normal tissues make it an ideal engineered tumor target. We therefore developed anti-CAR19 CAR T cells with the goal of specifically targeting CAR19+ B-ALL. Methods. We designed two anti-CAR19 CAR using an anti-CAR19 idiotype scFv (clone 136.20.1, original clone kind gift of Dr. Laurence Cooper) testing two light chain orientations for the scFv: light to heavy (L2H) and heavy to light (H2L). We cloned the constructs into our standard backbone containing the CD8 hinge and trans-membrane domains, 4-1BB costimulatory and CD3z signaling domain. The constructs were packaged into a lentiviral vector and used to transduce normal donor T cells. As target cells, we used ex-vivo expanded primary leukemic blasts from the CAR19-expressing relapsed patient (CHP-107), as well as a luciferase+ B-ALL cell line (NALM6) transduced with the full-length CAR19 used in our clinical studies. Of note, the expression of CAR19 in CD19+ NALM6 cells led to apparent loss of CD19 by flow cytometry. We tested CART function in vitro with luciferase-based killing assays and in vivo in human xenograft models using NOD-SCID gamma chain deficient (NSG) mice. Results. Both L2H and H2L anti-CAR19 CAR were efficiently expressed on T cells as detected by flow cytometry. In vitro CART-CAR19 efficiently killed CAR19-expressing B-ALL (NALM6) (L2H orientation: p Conclusions. The acquisition of CAR expression by leukemic cells during CART manufacturing is a rare event that generates a tumor-specific antigen, thereby presenting an opportunity for specific targeting without off-target toxicity. In addition, we hypothesize that anti-CAR19 CART could be used as an "antidote" to CAR19 T cells for those patients who have been in stable deep remission for several years, in order to deplete their CAR T cells and alleviate B cell aplasia. Disclosures Ruella: Novartis: Patents & Royalties, Research Funding. Lacey: Novartis: Research Funding; Genentech: Honoraria. Melenhorst: Novartis: Research Funding. June: Celldex: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Immune Design: Equity Ownership, Membership on an entity9s Board of Directors or advisory committees; WIRB/Copernicus Group: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Novartis: Patents & Royalties, Research Funding; Tmunity Therapeutics: Equity Ownership, Research Funding. Gill: Novartis: Patents & Royalties, Research Funding; CARMA Therapeutics: Consultancy, Equity Ownership, Research Funding.

Circulating anti-neutrophilic cytoplasmic autoantibodies targeting proteinase 3 (PR3-ANCA) are a diagnostic and pathogenic hallmark of granulomatosis with polyangiitis (GPA). It is, however, incompletely understood if inflamed tissue supports presence or emergence of PR3-ANCA+ B cells. In search of such cells in inflamed tissue of GPA, immunofluorescence staining for IgG and a common PR3-ANCA idiotype (5/7 Id) was undertaken. Few 5/7 Id+/IgG+ B cells were detected in respiratory and kidney tissue of GPA. To gain more insight into surrogate markers possibly indicative of an anti-PR3-response, a meta-analysis comprising IGVH and IGVL genes derived from respiratory tract tissue of GPA (231 clones) was performed. Next generation sequencing-based IGHV genes derived from peripheral blood of healthy donors (244.353 clones) and previously published IGLV genes (148 clones) served as controls. Additionally, Ig genes of three murine and five known human monoclonal anti-PR3 antibodies were analyzed. Primary and probably secondary rearrangements led to altered VDJ usage and an extended complementarity determining region 3 (CDR3) of IGHV clones from GPA tissue. Selection against amino acid exchanges was prominent in the framework region of IGHV clones from GPA tissue. The comparison of V(D)J rearrangements and deduced amino acid sequences of the CDR3 yielded no identities and few similarities between clones derived from respiratory tissue of GPA and anti-PR3 antibodies, arguing against a presence of B cells that carry PR3-ANCA-prone Ig genes among the clones. In line with the scarcity of 5/7 Id+ B lymphocytes in GPA tissue, the results suggest that with respect to a local anti-PR3 response, methods detecting rare clones are required.

Therapeutic antibodies are the fastest growing class of drugs in the treatment of cancer, and autoimmune and inflammatory diseases that require the concomitant development of assays to monitor therapeutic antibody levels. Here, we demonstrate that the use of Affimer nonantibody binding proteins provides an advantage over current antibody-based detection systems. For four therapeutic antibodies, we used phage display to isolate highly specific anti-idiotypic Affimer reagents, which selectively bind to the therapeutic antibody idiotype. For each antibody target the calibration curves met US Food and Drug Administration criteria and the dynamic range compared favorably with commercially available reagents. Affimer proteins therefore represent promising anti-idiotypic reagents that are simple to select and manufacture, and that offer the sensitivity, specificity and consistency required for pharmacokinetic assays.

Deficient antibody production in patients with common variable immunodeficiency (CVID) is accompanied by an inability to produce free light chains (FLCs), particularly kappa (κ) FLC, due to B-cell dysfunction. We found that intravenous immunoglobulin (IVIg) administration, in a patient with CVID and (κ) FLC deficiency, for o short period of only 6 months, induced after discontinuation of treatment some kind of “long-lasting active immunity”, leading to the secretion of immunoglobulin (κ) FLCs. A remarkable finding of our study is how effectively IVIg therapy led to a calculable (κ/λ) FLCs ratio, within the reference range. IVIg therapy may have functioned as an idiotype vaccine which induced a humoral response. To date, several questions remain open. For instance, from a clinical standpoint, we do not know whether this form of active immunotherapy has the potential to cure or just to control the immunoglobulin (κ) FLC deficiency. Further studies are necessary to confirm these findings.

Summary The heavy chain IGHV1-69 germline gene exhibits a high level of polymorphism and shows biased use in protective antibody (Ab) responses to infections and vaccines. It is also highly expressed in several B cell malignancies and autoimmune diseases. G6 is an anti-idiotypic monoclonal Ab that selectively binds to IGHV1-69 heavy chain germline gene 51p1 alleles that have been implicated in these Ab responses and disease processes. Here, we determine the co-crystal structure of humanized G6 (hG6.3) in complex with anti-influenza hemagglutinin stem-directed broadly neutralizing Ab D80. The core of the hG6.3 idiotope is a continuous string of CDR-H2 residues starting with M53 and ending with N58. G6 binding studies demonstrate the remarkable breadth of binding to 51p1 IGHV1-69 Abs with diverse CDR-H3, light chain, and antigen binding specificities. These studies detail the broad expression of the G6 cross-reactive idiotype (CRI) that further define its potential role in precision medicine., Graphical Abstract, Highlights • G6 binds to a subset of IGHV1-69 germline-based anti-influenza Abs • The structure of humanized G6 with a IGHV1-69 anti-influenza Ab is reported • Various binding assays further define the G6 cross-reactive binding idiotope • The core binding idiotope of G6 is deduced, G6 is an exceptional anti-idiotypic antibody that binds to antibodies encoded by the immunoglobulin heavy chain germline gene IGHV1-69. Avnir et al. describe how G6 binds to its cross-reactive idiotope by a set of binding assays and by solving the structure of humanized-G6 complexed with an IGHV1-69-anti-influenza Ab.

We consider self-tolerance and its failure -autoimmunity- in a minimal mathematical model of the idiotypic network. A node in the network represents a clone of B-lymphocytes and its antibodies of the same idiotype which is encoded by a bitstring. The links between nodes represent possible interactions between clones of almost complementary idiotype. A clone survives only if the number of populated neighbored nodes is neither too small nor too large. The dynamics is driven by the influx of lymphocytes with randomly generated idiotype from the bone marrow. Previous work has revealed that the network evolves towards a highly organized modular architecture, characterized by groups of nodes which share statistical properties. The structural properties of the architecture can be described analytically, the statistical properties determined from simulations are confirmed by a modular mean-field theory. To model the presence of self we permanently occupy one or several nodes. These nodes influence their linked neighbors, the autoreactive clones, but are themselves not affected by idiotypic interactions. The architecture is very similar to the case without self, but organized such that the neighbors of self are only weakly occupied, thus providing self-tolerance. This supports the perspective that self-reactive clones, which regularly occur in healthy organisms, are controlled by anti-idiotypic clones. We discuss how perturbations, like an infection with foreign antigen, a change in the influx of new idiotypes, or the random removal of idiotypes, may lead to autoreactivity and devise protocols which cause a reconstitution of the self-tolerant state. The results could be helpful to understand network and probabilistic aspects of autoimmune disorders., 30 pages, 27 figures

We report on the design of a phase I, non-randomized, open-label study of idiotypic DNA vaccination in patients with B-cell non-Hodgkin's lymphoma (ISRCTN31090206). The study uses DNA fusion gene vaccination encoding patient-specific single chain variable fragment, or idiotype, linked to an immunostimulatory sequence. Two types of immunostimulatory sequence are being explored: potato virus X coat protein and human chemokine MIP3α. Linear polyethylenimine with low molecular weight (8 kDa) is used as a synthetic vehicle for vaccine delivery. Humoral and T-cellular immune responses to vaccination will be measured by ELISA and ELISPOT, respectively. The primary study endpoints are safety, tolerability and immunogenicity of DNA-PEI vaccination.

In young adult BALB/c mice, antibodies to phosphorylcholine (PC) bearing the T15 (TEPC 15) idiotype confer protection against pneumococcal infections. In old age, even though PC reactive B cells are often increased, the proportion of T15+ antibodies declines. We hypothesize that limited surrogate light chain (SLC) and compromise of the pre-B cell receptor checkpoint in old mice contribute to both reduced new B cell generation and changes in the anti-PC antibodies seen in old age. In old mice: 1) early pre-B cell loss is most pronounced at the preBCR checkpoint; however, the reduced pool of early pre-B cells continues to proliferate consistent with preBCR signaling; 2) increased PC reactivity is seen in bone marrow immature B cells; 3) deficient SLC promotes increased B cell PC reactivity and diminished T15 idiotype within a subset of young adult mice; and 4) in old mice, as pre-B cell losses and reduced SLC become progressively more severe, increased T15 negative PC reactive B cells occur. These results associate a reduction in pre-B cells, imposed at the preBCR checkpoint, with increased reactivity to PC, but more limited expression of the protective T15 idiotype among PC reactive antibodies in old age.

The clonal B-cell immunoglobulin idiotype found on the surface of lymphomas was the first targeted tumor-specific antigen, and combinations of idiotype with classical and novel adjuvants were shown to stimulate robust humoral and cellular responses, though clinical efficacy was more variable. Cellular and in situ vaccination to help target a wider array of tumor-specific antigens have also been able to stimulate tumor-specific cellular responses, though their clinical success has also been limited. Our growing understanding of the role of regulatory cells and the immunosuppressive tumor microenvironment, along with a wide variety of immunomodulatory agents developed as of late, offer promising adjuvants to potentiate the immune responses elicited by these vaccine protocols and to achieve durable remissions.

The mechanisms for dominant T15 idiotype selection are not well understood, yet the significance of idiotypic regulation has been suggested. We proposed that to become dominant V regions of a given subset of B-1a cell must establish a functional idiotypic network with complementary T cells. Features required for the cells involved in immune network and steps preceding the establishment of clonal dominance are suggested. © 2018