scholarly journals Establishment of an inbred line of mice that express a synergistic immune defect precluding in vitro responses to type 1 and type 2 antigens, B cell mitogens, and a number of T cell-derived helper factors.

1983 ◽  
Vol 158 (5) ◽  
pp. 1401-1414 ◽  
Author(s):  
J J Mond ◽  
G Norton ◽  
W E Paul ◽  
I Scher ◽  
F D Finkelman ◽  
...  
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
C3h Mice ◽  
Immune Defect ◽  
T Cell Help

Introduction of the CBA/N X-linked gene into C3H mice has resulted in the establishment of a new strain of mice that has profound immunologic defects. B cells from these mice show significantly impaired in vitro immune responses to the T cell-independent type 1 antigen trinitrophenyl-Brucella abortus (TNP-BA) as well as markedly reduced proliferative responses to a number of B cell mitogens when compared with the responses of the parental control mice. The in vivo response of such mice to TNP-BA is, however, comparable to that of CBA/N mice. Furthermore, B cells from C3.CBA/N mice are unresponsive to the plaque-forming cell enhancing effects induced by EL4-derived supernatant in the presence of TNP-BA, unlike B cells obtained from CBA/N or C3H/Hen mice whose responsiveness to TNP-BA can be significantly enhanced in the presence of EL4-derived supernatant. The model we have presented to best explain these results suggests that B cells from C3.CBA/N mice can be stimulated only under conditions in which they can interact with carrier-specific T cell help and not under conditions where factor-dependent responses are dominant.

scholarly journals Autoreactive marginal zone B cells are spontaneously activated but lymph node B cells require T cell help

2006 ◽  
Vol 203 (8) ◽  
pp. 1985-1998 ◽  
Author(s):  
Laura Mandik-Nayak ◽  
Jennifer Racz ◽  
Barry P. Sleckman ◽  
Paul M. Allen
Keyword(s):  
Lymph Node ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Marginal Zone ◽  
B Cell Tolerance ◽  
Marginal Zone B Cells ◽  
T Cell Help

In K/BxN mice, arthritis is induced by autoantibodies against glucose-6-phosphate-isomerase (GPI). To investigate B cell tolerance to GPI in nonautoimmune mice, we increased the GPI-reactive B cell frequency using a low affinity anti-GPI H chain transgene. Surprisingly, anti-GPI B cells were not tolerant to this ubiquitously expressed and circulating autoantigen. Instead, they were found in two functionally distinct compartments: an activated population in the splenic marginal zone (MZ) and an antigenically ignorant one in the recirculating follicular/lymph node (LN) pool. This difference in activation was due to increased autoantigen availability in the MZ. Importantly, the LN anti-GPI B cells remained functionally competent and could be induced to secrete autoantibodies in response to cognate T cell help in vitro and in vivo. Therefore, our study of low affinity autoreactive B cells reveals two distinct but potentially concurrent mechanisms for their activation, of which one is T cell dependent and the other is T cell independent.

Cultured Human B Cell APCs Expanded Using Il-4 and CD40 Ligand Preferentially Promote a Type 2 T Cell Response to Alloimmune Stimulation.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2668-2668
Author(s):  
Abdul Tawab ◽  
Yoshiyuki Takahashi ◽  
Childs Richard ◽  
Kurlander J. Roger
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Response ◽  
Cd40 Ligand ◽  
T Cell Response ◽  
Ifn Γ

Abstract In vitro stimulation of human peripheral blood B cells with recombinant IL-4 and CD40 ligand (CD40L) markedly increases their expression of MHC and costimulatory molecules, thus enhancing antigenic peptide presentation to T cells. Because these cells proliferate extensively in vitro (unlike monocytes or dendritic cells), they represent a promising and convenient reagent for the generation and maintenance of antigen-specific T cells for use in a variety of experimental or therapeutic settings. However, the impact of this type of B cell APC on cytokine production by responder T cells has hitherto not been examined. To address this issue, we stimulated normal human T cells with either allogeneic B cells (generated in vitro) or with MNCs obtained from the same donor. After 7 days, T cells were washed and re-challenged with the same APCs. The resulting alloreactive cytokine response was measured using quantitative ELISPOT methods and expressed as the frequencies of IFN-γ, IL-4, and IL-5 producing cells per thousand responder cells added. B cell- and MNC-primed cell lines both produced vigorous lymphokine responses, but B cell-stimulated T cells consistently produced more IL-5 spots (mean of 265 vs. 98/1000 responders, p<0.002) and fewer IFN-γ spots (163 vs 386/1000 cells, p<0.005) than MNC-stimulated cells. Further, the ratio of IFN-γ to IL-5 spots was almost ten-fold lower in B cell-stimulated cultures compared to MNC-induced cultures (0.67 vs. 5.2, p<0.001). ELISPOT studies assessing the ratio of IFN-γ to IL-4 spots and ELISA assays comparing IFN-γ and IL-5 levels from culture supernatants demonstrated the same pattern of marked type 2 skewing by B cells. This pattern was unaffected by the presence of anti-IL-4 antibody suggesting type 2 skewing was not mediated by IL-4. Cytokine skewing produced by B cells or MNC could be partially reversed by swapping MNC and B cells during re-stimulation on day 7, but this plasticity was markedly reduced after 3 (weekly) cycles of B cell or MNC re-stimulation in vitro. Type 2 skewing by B cells was enhanced when monocytes were removed from responder T cell populations by either depleting CD14+ positive cells or by positive selection of T cells prior to stimulation. In contrast, type 2 polarization could be prevented using recombinant IL-12. Not all cells of B-cell origin share the same propensity to type 2 skewing observed with IL-4/CD40L-stimulated B cells; under identical conditions, EBV-transformed B cells stimulated alloimmune T cells to produce a strong type 1 cytokine response comparable to that produced by MNCs. In summary, IL-4/CD40L-stimulated B cells strongly promote a type 2 T cell response during primary alloimmune challenge; this skewing can become fixed after repeated B cell stimulation. Investigators using these cells as APC should be aware of this potential phenomenon, particularly during primary T cell responses. It is also important to consider the factors described above that may exacerbate or ameliorate this effect.

scholarly journals Enhanced B Cell Expansion, Survival, and Humoral Responses by Targeting Death Receptor 6

2002 ◽  
Vol 197 (1) ◽  
pp. 51-62 ◽  
Author(s):  
Clint S. Schmidt ◽  
Jinqi Liu ◽  
Tonghai Zhang ◽  
Ho Yeong Song ◽  
George Sandusky ◽  
...  
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Expansion ◽  
Death Receptor ◽  
Immunoglobulin M ◽  
Type I ◽  
Factor C

Targeted disruption of death receptor (DR)6 results in enhanced CD4+ T cell expansion and T helper cell type 2 differentiation after stimulation. Similar to T cells, DR6 is expressed on resting B cells but is down-regulated upon activation. We examined DR6−/− B cell responses both in vitro and in vivo. In vitro, DR6−/− B cells undergo increased proliferation in response to anti–immunoglobulin M, anti-CD40, and lipopolysaccharide. This hyperproliferative response was due, at least in part, to both increased cell division and reduced cell apoptosis when compared with wild-type B cells. Consistent with these observations, increased nuclear levels and activity of nuclear factor κB transcription factor, c-Rel, and elevated Bcl-xl expression were observed in DR6−/− B cells upon stimulation. In addition, DR6−/− B cells exhibited higher surface levels of CD86 upon activation and were more effective as antigen-presenting cells in an allogeneic T cell proliferation response. DR6−/− mice exhibited enhanced germinal center formation and increased titers of immunoglobulins to T-dependent as well as T-independent type I and II antigens. This is the first demonstration of a regulatory role of DR6 in the activation and function of B cells.

scholarly journals Outer Periarteriolar Lymphoid Sheath Arrest and Subsequent Differentiation of Both Naive and Tolerant Immunoglobulin Transgenic B Cells Is Determined by B Cell Receptor Occupancy

1997 ◽  
Vol 186 (5) ◽  
pp. 631-643 ◽  
Author(s):  
Matthew C. Cook ◽  
Antony Basten ◽  
Barbara Fazekas de St. Groth
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Receptor Occupancy ◽  
Cell Receptor ◽  
Antigen Concentration ◽  
Identical Manner ◽  
T Cell Help ◽  
Self Antigen

T-dependent B cell responses in the spleen are initiated in the outer periarteriolar lymphoid sheath (PALS) and culminate in the generation of proliferative foci and germinal center reactions. By pulsing anti–hen egg lysozyme (HEL) immunoglobulin transgenic (IgTg) B cells with various concentrations of HEL in vitro before adoptive transfer into normal recipients, it was shown that a critical number of B cell receptors (BCRs) must be ligated for B cells to undergo arrest in the outer PALS. T cell help was manipulated independently of the BCR stimulus by incubating B cells expressing the appropriate major histocompatibility complex class II antigen with a peptide recognized by CD4+ TCR Tg T cells. B cells which either failed to arrest in the outer PALS due to a subthreshold BCR stimulus, or arrested only transiently due to the brevity of the BCR stimulus, underwent an abortive response within the follicles when provided with T cell help. In contrast, naive B cells stimulated by a sustained, suprathreshold concentration of either foreign or self-antigen and given T cell help, proliferated in the outer PALS and then differentiated. Outer PALS arrest was not influenced by the nature of the B cells occupying the follicle, but appeared to be determined solely by the magnitude of BCR stimulation. Thus antigen-pulsed B cells arrested in the outer PALS in an identical manner irrespective of whether the follicles comprised a population of normal B cells with multiple specificities, a monoclonal naive population, or a monoclonal population of tolerant B cells. In addition, tolerant B cells were found to relocate from the follicles to the outer PALS of HEL/anti-HEL double Tg mice in which the concentration of soluble self-antigen had been increased by zinc feeding. Similarly, when anti-HEL Tg mice were crossed with a second HEL Tg strain expressing a higher concentration of soluble HEL, the tolerant anti-HEL Tg B cells were located constitutively in the outer PALS. Thus, subtle variations in antigen concentration resulted in dramatic changes in positioning of B cells within the spleen. A series of mixed bone marrow chimeras in which the effective antigen concentration was inversely related to the number of self-reactive B cells due to absorption of antigen by transgene-encoded membrane and secreted Ig, was used to confirm that alteration in B cell position previously attributed to changes in follicular composition could be explained on the basis of available antigen concentration, rather than the diversity of the repertoire.

In Vitro and in Vivo Imaging of Initial T-B Cell Interactions in the Setting of B Cell-Based Cancer Immunotherapy

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2740-2740
Author(s):  
Kerstin Wennhold ◽  
Nela Klein-Gonzalez ◽  
Michael von Bergwelt-Baildon ◽  
Alexander Shimabukuro-Vornhagen
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cancer Immunotherapy ◽  
Cell Interactions ◽  
Migration Behavior ◽  
Cell Zone

Abstract In recent years, there has been a growing interest in the use of B cells for cellular immunotherapy, since B cell-based cancer vaccines have yielded promising results in preclinical animal models. Contrary to dendritic cells (DCs), we know little about the migration behavior of B cells in vivo. Therefore, we investigated the interactions between CD40-activated (CD40) B cells and cytotoxic T cells in vitro and the migration behavior of CD40B cells in vivo. The dynamic interactions of human antigen-presenting cells and antigen-specific T cells were observed by time-lapse videomicroscopy. The migratory and chemoattractant potential of CD40B cells was analyzed by flow cytometry and standard transwell migration assays. GFP+ CD40B cells or CD40B cells isolated from Luciferase+mice were used for subsequent in vivo studies. Murine CD40B cells show similar migratory and chemotactic characteristics compared to human CD40B cells. Upon CD40-activation, B cells upregulate the important molecules involved in lymh node homing (CD62L, CCR7/CDCR4), which are functional and induce chemotaxis of T cells in vitro. Striking differences were observed for interactions of human CD40B cells or DCs with T cells. Antigen-loaded CD40B cells differ from immature and mature DCs by displaying a rapid migratory pattern undergoing highly dynamic, short-lived (7.5 min) and sequential interactions with cognate T cells. In vivo, CD40B cells migrate to the spleen and the lymph nodes, where they enrich in the B cell zone before traveling to B cell/ T cell boundary close to the T cell zone. CD40B cell interactions with T cells are dynamic and short-lived and thereby differ from DCs. Taken together, the migration behavior of CD40B cells and their interaction with T cells underline their potential as cellular adjuvant for cancer immunotherapy. Disclosures No relevant conflicts of interest to declare.

scholarly journals Role of the major histocompatibility complex in T cell activation of B cell subpopulations. lyb-5(+) and lyb-5(-) B cell subpopulations differ in their requirement for major histocompatibility complex-restricted T cell recognition

1981 ◽  
Vol 154 (2) ◽  
pp. 501-516 ◽  
Author(s):  
A Singer ◽  
PJ Morrissey ◽  
KS Hathcock ◽  
A Ahmed ◽  
I Scher ◽  
...  
Keyword(s):  
Major Histocompatibility Complex ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Recognition ◽  
Major Histocompatibility ◽  
Histocompatibility Complex ◽  
Cell Subpopulations

This report has examined the requirements for T helper (T(H)) cell recognition of major histocompatibility complex (MHC) determinants expressed by B cells for the activation of unprimed Lyb-5(+) and Lyb-5(-) B cell subpopulations . The generation of primary T(H) cell-dependent plaque-forming cell responses in vitro microculture required the presence of Lyb-5(+) B cells because B cell populations that were deprived, either genetically or serologically, of the Lyb-5(+) subpopulation were not activated in these responses. Cell-mixing experiments in which A X B {arrow} A chimeric T(H) cells were mixed with purified populations of parental accessory cells and parental B cells demonstrated that the in vitro activation of Lyb-5(+) B cells did not require T(H) cell recognition of B cell MHC determinants, although it did require T(H) cell recognition of accessory cell MHC determinants . In contrast to the failure of Lyb-5(-) B cells to be activated in primary T(H) cell-dependent responses in vitro microculture, isolated populations of Lyb-5(-) B cells were triggered by T(H) cells in vivo in short-term adoptive transfer experiments . By the use of A X B {arrow} A chimeric T(H) cells and parental strain B adoptive hosts, it was possible in vivo to distinguish genetically restricted T(H) cell recognition of B cells from genetically restricted T(H) cell recognition of accessory cells. Similar to the results obtained in vitro, the activation in vivo of unfractionated (Lyb-5(+) plus Lyb-5(-)) B cell populations did not require T(H) cell recognition of B cell MHC determinants . In contrast, in the same in vivo responses activation of isolated populations of Lyb-5(-) B cells did require T(H) cell recognition of B cell MHC determinants. The most straightforward interpretation of these experiments is that T(H) cell recognition of B cell MHC determinants is required for the activation of Lyb-5(-) B cells but is not required for the activation of Lyb-5(+) B cells . To better understand why T(H) cell activation of one B cell subpopulation is genetically restricted, whereas activation of another subpopulation is not, the response of Lyb-5(+) and Lyb-5(-) B cells to the soluble activating factors present in concanavalin A-induced spleen cell supernates (Con A SN) was examined. It was observed that Lyb-5(-) B cells, as opposed to Lyb-5(+) B cells, were unable to respond in microculture to the nonspecific T(H) cell- activating factors present in Con A SN, even though they were able to nonspecifically respond under the same conditions to trinitrophenyllipopolysaccharide. It was observed that the ability of B cell subpopulations to respond to nonspecific soluble T cell factors paralleled their ability to be activated by T(H) cells in a genetically unrestricted manner. Thus, the present experiments demonstrate that activation by T(H) cells of Lyb-5(-) B cells is MHC restricted, whereas activation of Lyb-5(+) B cells is not. These experiments suggest that one possible explanation for such differences is that activation of Lyb-5(+) B cells does not require direct interaction with T(H) cells because they can be activated by soluble activation signals that T(H) cells secrete.

scholarly journals Idiotype profile of an immune response. II. Reversal of the relative dominance of major and minor cross-reactive idiotypes in arsonate-specific T-independent responses.

1983 ◽  
Vol 158 (2) ◽  
pp. 438-451 ◽  
Author(s):  
J D Conger ◽  
E Lamoyi ◽  
G K Lewis ◽  
A Nisonoff ◽  
J W Goodman
Keyword(s):  
T Cell ◽  
B Cell ◽  
Hyperimmune Serum ◽  
Relative Dominance ◽  
Cell Subpopulations ◽  
Weak Expression ◽  
B Cell Subsets

Two different cross-reactive idiotype (CRI) groups are distinguishable in the Ab response of A/J mice to the p-azobenzenearsonate (ABA) hapten: CRIA and CRIm. These two groups showed distinct patterns of relative dominance in the ensuing response depending on whether the inducing Ag was a T cell-dependent (TD) form of ABA, such as ABA-KLH or ABA-CGG, or a T-independent type 1 (TI-1) form, such as ABA-Brucella abortus or ABA-lipopolysaccharide (LPS), and on whether the response was elicited in vivo or in vitro. The CRI+ component of primary in vivo plaque-forming cell (PFC) responses to TD ABA Ags was largely (greater than 90%) CRIA+ as was, to a slightly lesser extent (greater than 75%) the CRI+ portion of secondary or hyperimmune serum Ab or PFC responses to the same Ags. In contrast, in vivo primary and hyperimmune PFC responses to ABA-Bru or ABA-LPS showed a significantly lower CRIA/CRI ratio, averaging 0.5-0.6, with some individual mice giving figures as low as 0.2, indicating predominance of CRIm over CRIA. Serological analysis of hyperimmune anti-ABA Abs from a group of 5 A/J mice immunized with ABA-Bru gave a figure of less than 0.5 for the CRIA/CRI ratio. The most striking disparity from the TD pattern was seen in primary in vitro PFC responses to the TI ABA Ags; here ratios of less than 0.2 were generally seen. Since T cell removal did not alter the Id pattern in the TI responses, CRIA-specific Ts cells do not account for the weak expression of CRIA in such responses. We propose a model that explains these results on the basis of differential expression of IdX dominance by two distinct B cell subpopulations--equatable to the Lyb-5+ and Lyb-5- B cell subsets--along with differential relative activation of these subsets in different types of responses. Examination of anti-ABA PFC responses of F1 progeny of CBA/N and A/J mice to ABA-Bru lends support to this hypothesis since CRIA expression was significantly lower in mice with the xid defect.

EBV Can Induce Somatic Hypermutation in Naïve B Cells In Vitro but Ig Class Switching Requires T Cell Help.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2370-2370
Author(s):  
Sridhar Chaganti ◽  
Noelia Begue Pastor ◽  
Gouri Baldwin ◽  
Claire Shannon-Lowe ◽  
Regina Feederle ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Germ Line ◽  
Somatic Hypermutation ◽  
Memory B Cells ◽  
Class Switching ◽  
B Cell Subsets ◽  
T Cell Help

Abstract Following primary infection, Epstein-Barr virus (EBV) establishes life long persistence in the host IgD− CD27+ memory B cell compartment rather than the IgD+ CD27+ marginal zone (MZ)-like or the IgD+ CD27− naïve B cell compartments. One possible explanation for such exclusive persistence in memory B cells is that EBV preferentially infects memory B cells. Alternatively, the virus may infect all B cell subsets but then drive MZ and naïve B cells to acquire the Ig isotype-switched phenotype and hypermutated Ig genotype of memory cells. Here we ask whether there is any evidence for one or other hypothesis from in vitro experiments. B cells from healthy donor blood samples were FACS sorted on the basis of IgD/CD27 expression into naïve, MZ, and memory B cell subsets with purities of >99%, >97% and >98% respectively. Analysis of the IgVH sequence further confirmed purity of the FACS sorted B cell subsets. Accordingly, 102 of 105 IgVH sequences amplified from purified naïve B cells were germ-line where as the vast majority of sequences amplified from MZ and memory B cells were mutated. All three B cell subsets expressed equal amounts of CD21 (EBV receptor on B cells), bound similar amounts of virus, and transformed with equal efficiency to establish B lymphoblastoid cell lines (LCLs) in vitro. Naïve B cell transformants upregulated CD27 expression but retained the IgM+, IgD+ phenotype as determined by FACS analysis and RT-PCR; MZ-B derived LCLs likewise were IgM+, IgD+, CD27+; and memory-B derived LCLs were consistently CD27+, IgD− and expressed either IgG, IgA or in some cases IgM. Therefore, EBV infection per se did not induce class switching. However, both naïve and MZ-B derived LCLs could still be induced to switch to IgG in the presence of CD40 ligand and IL-4; signals that are normally provided by T cells in vivo. To assess if EBV infection might drive Ig hypermutation, we carried out IgVH sequence analysis on the naïve-B derived LCL clones. Interestingly, 42 of 114 clonal IgVH sequences amplified from naïve-B derived LCLs had 3 or more mutations and the patterns of mutation seen were consistent with that produced by somatic hypermutation (SHM). Furthermore, within some naïve-B cell derived LCL clones, there were both germ-line and mutated sequences all sharing the same VDJ rearrangement (CDR3 sequence), again implying sequence diversification following EBV transformation of a single naïve B cell. Some intraclonal variation of the already hypermutated IgVH sequence was also noted in memory and MZ-B derived LCLs further suggesting ongoing mutational activity. Consistent with this, activation-induced cytidine deaminase (AID) expression was upregulated in transformants as assessed by real time RT-PCR. Our in vitro data is therefore compatible with a model of EBV persistence where the virus infects all mature B cell subsets but then drives infected naïve B cells to acquire a memory genotype by inducing SHM. In addition, EBV infected naïve and MZ-B cells may undergo Ig class switching to acquire the IgD− CD27+ memory phenotype in the presence of T cell help in vivo. EBV’s ability to induce SHM may also contribute to the lymphomagenic potential of the virus in addition to its B cell transforming and growth promoting properties.

Prediction of MHC Class I-Restricted Immunogenic Epitopes of B-Cell Receptors Indicates T Cell-Mediated Immunosurveillance of Malignant B Cell Clones.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1949-1949
Author(s):  
Anna-Maria Strothmeyer ◽  
Marcus Duehren-von Minden ◽  
Marcelo A Navarrete ◽  
Kristina Heining-Mikesch ◽  
Hendrik Veelken
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Mhc Class I ◽  
Cell Activity ◽  
Class I ◽  
Cell Responses ◽  
Hla Haplotypes

Abstract Abstract 1949 Poster Board I-972 Tumor-specific immune responses can be induced in patients with indolent B cell lymphomas (iNHL) by active immunization against the individual B cell receptor (BCR) expressed by the malignant B cell clone, the so-called “idiotype” (Id). In subsequent trials of intradermal vaccination with recombinant lymphoma-derived Fab fragment in iNHL, we have studied the specificity of MHC class I-restricted anti-Id T cell responses by epitope mapping experiments with synthetic Id-derived peptides predicted to be presented by the respective patient's HLA complex. While such peptides exist in hypervariable and conserved Id regions, these assays have shown consistently that in vivo-induced T cell responses occur preferentially against individual Id epitopes located in complementarity-determining regions (CDR), whereas framework (FR) and constant region-derived epitopes are ignored (Bertinetti et al., Cancer Res. 2006; Navarrete et al., ASH 2008). These results contrast with in vitro studies showing that FR-derived peptides are excellent targets for cytotoxic T cells in iNHL patients (Trojan et al., Nat Med 2000). To gain further insight into the relative predominance and immunological role of MHC class I-restricted Id epitopes, we conducted a comprehensive reverse immunology study in follicular lymphoma (FL). Clonal and functional IgH chain transcript sequences were identified from tumor biopsies of 39 FL patients by A-PCR (Bertinetti et al., EJH 2006). The HLA-A and B haplotype of the patients was determined by conventional serological testing and high-resolution PCR genotyping. Potentially MHC-presentable peptides from all Id sequences and their corresponding germ-line (GL) VH genes were identified for the HLA haplotypes of all 39 patients by reverse immunology (bimas.cit.nih.gov). Identified peptides were ranked for each haplotype according to their predicted score, and the sum of the scores for the 20 highest ranking peptides was calculated. The sum score for any given Id was compared to the mean of the sum scores of the other 38 Ids on the respective patient's HLA haplotypes. Separate analyses were performed for CDR peptides (containing at least 2 AA in any CDR) versus non-CDR-peptides (allocated through imgt.cines.fr), Id versus GL sequences, and Id versus contaminating sporadic Ig sequences that represent bona fide normal B cells in the biopsies. 72% of all peptides with BIMAS scores of ≥50 and ≥10, respectively, were located in FR, expecially in FR3. The ranked sum Id scores were lower for the patients' own tumor Id than for the mean of the allogeneic Ids (Table; Wilcoxon's matched pair test). This difference was mostly attributable to CDR-derived epitopes throughout all CDRs despite overall lower immunogenicity compared to FR. There was no evidence for differential immunogenicity between a hypermutated FL Id and the corresponding GL (p=0.58). Finally, a preliminary survey of IgH sequences from non-clonal B cells indicated similar immunogenicity compared to FL Id (p=0.31). These bioinformatic findings indicate T cell-mediated immunosurveillance against the BCR of malignant and perhaps nonmalignant B cells. T cell activity appears to be directed predominantly against individual CDR peptides despite their lesser predicted HLA binding capacity compared to FR peptides. Existing CDR epitopes are not generated during the hypermutation process of BCRs, raising the possibility that randomly generated, more immunogenic hypervariable peptides are not permitted by the immune system. In conjunction with the T cell activity observed in in vivo and in vitro studies cited above, these findings are consistent with strong peripheral tolerance to shared Id structures. On the other hand, T cell control of individual Id peptides may play a role in immunosurveillance of malignant B cells and may be exploited for active immunotherapy of lymphoma. In contrast, generic or pan-B-cell epitopes are predicted to be less effective in inducing anti-lymphoma T cell responses.Median (range) BIMASPatient IdMean of allogeneic IdscomparisonAll peptides213 (40-5920)369 (56-5520)p=0.0012FR peptides157 (20-5415)239 (18-3891)p=0.045CDR peptides74 (7-648)175 (21-1760)p<0.0001- CDR1 peptides21 (0.7-144)52 (1.9-630)p=0.0007- CDR2 peptides7.6 (0.2-345)30 (2.2-212)p=0.0089- CDR3 peptides16 (1.3-506)37 (6-980)p=0.0008 Disclosures: No relevant conflicts of interest to declare.

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