scholarly journals Cellular and genetic control of antibody responses. V. Helper T-cell recognition of H-2 determinants on accessory cells but not B cells.

1979 ◽  
Vol 149 (5) ◽  
pp. 1208-1226 ◽  
Author(s):  
A Singer ◽  
K S Hathcock ◽  
R J Hodes
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
Helper T Cells ◽  
Cell Recognition ◽  
Helper T Cell ◽  
T Cell Recognition ◽  
Accessory Cells

Requirements for helper T-cell recognition of H-2 determinants expressed on adherent accessory cells and on B cells was individually assessed in the anti-hapten PFC responses to TNP-KLH. Complicating allogeneic effects were minimized or avoided by the use of helper T cells from normal F1 hybrids, parent leads to F1 chimeras, and F1 leads to parent chimeras. The results of both in vitro and in vivo experiments demonstrated that: (a) helper T cells are not required to recognize the identical H-2 determinants on both accessory cells and B cells; (b) helper T cells are required to recognize K or I-A region-encoded determinants expressed on accessory cells; (c) no requirement was observed in vitro or in vivo for helper T-cell recognition of B-cell-expressed H-2 determinants; and (d) no requirement was observed for H-2 homology between accessory cells and B cells. The absence of required helper T-cell recognition of the identical H-2 determinants on both accessory cells and B cells was demonstrated in two ways: (a) naive of KLH-primed (A x B)F1 hybrid helper T cells collaborated equally well with B cells from either parentA or parentB in the presence of accessory cells from either parent; (b) A leads to (A x B)F1 chimeric spleen cells depleted of accessory cells collaborated equally well with accessory cells from either parentA or parentB, even though the B cells only expressed the H-2 determinants of parentA. A requirement for helper T-cell recognition of K or I-A region-encoded H-2 determinants on accessory cells was also demonstrated in two ways: (a) (A x B)F1 leads to parentA chimeric spleen cells depleted of accessory cells collaborated with accessory cells from parentA but not parentB; and (b) (A x B)F1 leads to parentA chimeric helper T cells collaborated with normal F1 B cells only in the presence of parental or recombinant accessory cells that expressed the K or I-A region-encoded determinants of parentA. Although restricted in their ability to recognize H-2 determinants on accessory cells, it was demonstrated both in vitro and in vivo that (A x B)F1 leads to parentA chimeric helper T cells were able to collaborate with B cells from either parentA or parentB. In vitro in the presence of accessory cells from parentA, (A x B)F1 leads to parentA chimeric helper T cells collaborated equally well with B cells from either parent. In addition, the inability of (A x B)F1 leads to parentA chimeric helper T cells to collaborate with (B + accessory) cells from parentB was successfully reversed by the addition of parentA SAC as added accessory cells. In vivo, upon the addition of parentA accessory cells, (A x B)F1 leads to parentA chimeric helper T cells collaborated with parentB B cells in short-term adoptive transfer experiments.

scholarly journals The role of H-2-linked genes in helper T-cell function. I. In vitro expression in B cells of immune response genes controlling helper T-cell activity

1977 ◽  
Vol 146 (6) ◽  
pp. 1748-1764 ◽  
Author(s):  
JW Kappler ◽  
P Marrack
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cross Reaction ◽  
Helper T Cells ◽  
Helper T Cell ◽  
Low Responder ◽  
The Cross

The ability of murine helper T cells primed to the antigen, sheep erythrocytes (SRBC) to cross-react with burro erythrocytes (BRBC) in the in vitro anti-trinitrophenol (TNP) response to TNP-RBC was shown to be under genetic control. Although non-H-2 genes were shown to influence the absolute level of helper activity assayed after SRBC priming, the extent of cross-reaction of SRBC-primed helpers with BRBC was shown to be controlled by an H-2-1inked Ir gene(s). H-2 haplotypes were identified which determined high, intermediate, or low response to the cross- reacting determinants and the gene(s) controlling the cross-reaction tentatively mapped to the K through I-E end of the H-2 complex. Helpers primed in F(1) mice of high x intermediate or high x low responder parents were tested for cross-reaction using B cells and macrophages (Mφ) of parental haplotypes. In each case the extent of cross-reaction was predicted by the H-2 haplotype of the B cells and Mφ, establishing the expression of the Ir gene(s) in B cells and/or Mφ a t least, but not ruling out its expression in T cells as well. The low cross-reaction seen when T cells from F(1) mice of high × low responder parents were tested on low responder B cells and Mφ was not increased by the presence of high responder Mφ, indicating the Ir gene(s) is expressed in the B cell a t least although it may be expressed in Mφ as well. These and our previously reported experiments are consistent with the hypothesis that helper T cells recognize antigen bound to the surface of B cells and Mφ in association with the product(s) of Ir gene(s) expressed on the B cell and Mφ.

scholarly journals Major histocompatibility complex-restricted self recognition. A monoclonal anti-I-Ak reagent blocks helper T cell recognition of self major histocompatibility complex determinants.

1980 ◽  
Vol 152 (6) ◽  
pp. 1779-1794 ◽  
Author(s):  
R J Hodes ◽  
K S Hathcock ◽  
A Singer
Keyword(s):  
T Cells ◽  
T Cell ◽  
Antibody Responses ◽  
Accessory Cell ◽  
Cell Recognition ◽  
T Cell Recognition ◽  
Histocompatibility Complex ◽  
Accessory Cells ◽  
Ia Antigens

The functional role of cell surface Ia antigens has been studied for in vitro antibody responses, using as a probe the ability of anti-Ia reagents to inhibit these responses. A hybridoma monoclonal anti-Ia reagent specific for a product of I-Ak (Ia.17) profoundly inhibited in vitro antibody responses to TNP-KLH by spleen cells of the I-Ak but not I-Ab haplotype. This inhibition by anti-I-Ak product, but not by interaction with T or B cell product, in spite of the fact that functional B cells as well as accessory cells could be shown to express the determinant detected by this hybridoma reagent. These results suggest that the Ia expressed by accessory cells in of unique functional importance in these responses. To further characterize the function of Ia antigens in this response system, the mechanism of anti-I-Ak inhibition was determined. The inhibition resulting from interaction of anti-I-Ak with accessory cell Ia was not mediated by nonspecific suppressor cells, nor was there nonspecific interference with accessory cell function as a result of the binding of anti-Ia antibody. The relationship between anti-Ia inhibition and T helper cell recognition of self determinations on accessory cells was analyzed using T cells from radiation bone marrow chimeras. It was demonstrated that (B10 X B10.A)F1 leads to B10 (F1 leads to B10) chimera T cells were able to cooperate with B10 (H-2b and I-Ab) but not B10.A (H-2a and I-Ak) accessory cells for responses to TNP-KLH; F1 leads to B10.A T cells were able to cooperate with B10.A but not B10 accessory cells; and both chimera populations were able to cooperate with (B10 X B10.A)F1 (F1) accessory cells. Monoclonal anti-I-Ak inhibited the cooperation of F1 leads to B10.A T cells with the same F1 accessory cells. Thus, inhibition by anti-I-Ak is dependent upon active helper T cell recognition of I-Ak-encoded determinants expressed on accessory cells. These findings demonstrate that T cells recognize self Ia determinants expressed on accessory cells, and that such recognition is required for the generation of T cell-dependent antibody responses.

scholarly journals P01.02 TLR-mediated suppression of the CCL22-CCR4 axis as a new target for tumor immunotherapy

2021 ◽  
Vol 9 (Suppl 1) ◽  
pp. A3.2-A4
Author(s):  
J Grün ◽  
I Piseddu ◽  
C Perleberg ◽  
N Röhrle ◽  
S Endres ◽  
...  
Keyword(s):  
T Cells ◽  
Dendritic Cells ◽  
T Cell ◽  
B Cells ◽  
Regulatory T Cells ◽  
Type I ◽  
List Type ◽  
Gm Csf

BackgroundUnmethylated CpG-DNA is a potent ligand for the endosomal Toll-like-receptor-9, important for the immune activation to pathogen-associated molecules.1 CpG and other TLR-ligands show effective immunotherapeutic capacities in cancer treatment by inducing an antitumorigenic immunity.2 They are able to reduce tumor progression by reduction of intratumoral secretion of the immunoregulating chemokine CCL223 and subsequent recruitment of immunosuppressive regulatory T cells (Treg), which express CCR4 the only so far known receptor for CCL22.4 Our recent work has shown that CCL22 secretion by dendritic cells (DC) in the lymph node, mediates tolerance by inducing DC-Treg contacts.5 Indeed, in the absence of CCL22, immune responses to vaccination were stronger and resulted in tumor rejection.6 Therefore, we are aiming to investigate the effects of TLR-ligands on systemic CCL22 levels, elucidating all involved mechanisms to identify new targets for cancer immunotherapy.Materials and MethodsT, B and CD11c+ DCs of wildtype (wt) and RAG1-/- mice were isolated from splenocytes by magnetic-activated cell sorting for in vitro assays. Different co-cultures were incubated with CpG and GM-CSF, known as an CCL22 inducer.5 For in vivo experiments, wt mice were treated with CpG, R484 or poly(I:C) alone and in combination with GM-CSF. CCL22-levels in a number of organs were analyzed.ResultsAnalyzing the different immune cell compartments in vitro, we found that DCs in whole splenocytes secrete CCL22 during culture while DC cultured alone showed no CCL22 secretion. When treated with CpG, CCL22-levels were reduced in splenocytes, while it was induced in DC culture alone. The same results were seen when RAG splenocytes, that lack functional B and T cells, were cultured with CpG. CpG treated B cells were able to suppress CCL22 secretion by DC unlike T cells alone. Co-cultures of T and B cells treated with CpG, however, induced the strongest CCL22 suppression in DC. In vivo, we could show that all TLR ligands tested reduced CCL22 in a number of organs significantly. Furthermore, CpG showed the strongest suppression of CCL22 even in the presence of the CCL22 inducer GM-CSF.5ConclusionsWe could show that B cells with T cells mediate CCL22 suppression by TLR ligands. The fact that CpG was able to reduce CCL22 levels even in the presence of the inducer GM-CSF demonstrates the potent CCL22 suppressive capacity of TLR ligands.ReferencesO’Neill LA, et al. The history of toll-like receptors – redefining innate immunity. Nat Rev Immunol 2013;13(6):453–60.Rothenfusser S, et al. Recent advances in immunostimulatory CpG oligonucleotides. Curr Opin Mol Ther 2003;5(2):98–106.Wang S, et al. Intratumoral injection of a CpG oligonucleotide reverts resistance to PD-1 blockade by expanding multifunctional CD8+ T cells. Proc Natl Acad Sci U S A 2016;113(46): E7240–E7249.Rapp M, et al. CCL22 controls immunity by promoting regulatory T cell communication with dendritic cells in lymph nodes. J Exp Med 2019;216(5):1170–1181.Piseddu I, et al. Constitutive expression of CCL22 is mediated by T cell-derived GM-CSF. J Immunol 2020;205(8):2056–2065.Anz D, et al. Suppression of intratumoral CCL22 by type i interferon inhibits migration of regulatory T cells and blocks cancer progression. Cancer Res 2015;75(21):4483–93.Disclosure InformationJ. Grün: None. I. Piseddu: None. C. Perleberg: None. N. Röhrle: None. S. Endres: None. D. Anz: None.

scholarly journals Genetic control of immune response to myoglobin. Ir gene function in genetic restriction between T and B lymphocytes.

1982 ◽  
Vol 156 (5) ◽  
pp. 1486-1501 ◽  
Author(s):  
Y Kohno ◽  
J A Berzofsky
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
High Responder ◽  
Gene Control ◽  
Gene Defect ◽  
Genetic Restriction ◽  
Low Responder

We studied the genetic restrictions on the interaction between T cells, B cells, and antigen-presenting cells (APC) involved in the H-2-linked Ir gene control of the in vitro secondary antibody response to sperm whale myoglobin (Mb) in mice. The B cells in this study were specific for Mb itself, rather than for a hapten unrelated to the Ir gene control, as in many previous studies. Low responder mice immunized in vivo with Mb bound to an immunogenic carrier, fowl gamma globulin (F gamma G), produced B cells competent to secrete anti-Mb antibodies in vitro if they received F gamma G-specific T cell help. However, (high-responder X low responder) F1 T cells from Mb-immune mice did not help these primed low responder (H-2k or H-2b) B cells in vitro, even in the presence of various numbers of F1 APC that were demonstrated to be component to reconstitute the response of spleen cells depleted by APC. Similar results were obtained with B6 leads to B6D2F1 radiation bone marrow chimeras. Genotypic low responder (H-2b) T cells from these mice helped Mb-primed B6D2F1B cells plus APC, but did not help syngeneic chimeric H-2b B cells, even in the presence of F1 APC. In contrast, we could not detect any Ir restriction on APC function during these in vitro secondary responses. Moreover, in the preceding paper, we found that low responder mice neonatally tolerized to higher responder H-2 had competent Mb-specific helper T cells capable of helping high responder but not low responder B cells and APC. Therefore, although function Mb-specific T cells and B cells both exist in low responder mice, the Ir gene defect is a manifestation of the failure of syngeneic collaboration between these two cell types. This genetic restriction on the interaction between T cells and B cells is consistent with the additional new finding that Lyb-5-negative B cells are a major participant in ths vitro secondary response because it is this Lyb-5-negative subpopulation of B cells that have recently been shown to require genetically restricted help. The Ir gene defect behaves operationally as a failure of low responder B cells to receive help from any source of Mb-specific T cells either high responder, low responder, or F1. The possible additional role of T cell-APC interactions, either during primary immunization in vivo or in the secondary culture is discussed.

scholarly journals Enhancement in Specific CD8+ T Cell Recognition of EphA2+ Tumors In Vitro and In Vivo after Treatment with Ligand Agonists

2008 ◽  
Vol 181 (11) ◽  
pp. 7721-7727 ◽  
Author(s):  
Amy K. Wesa ◽  
Christopher J. Herrem ◽  
Maja Mandic ◽  
Jennifer L. Taylor ◽  
Cecilia Vasquez ◽  
...  
Keyword(s):  
T Cell ◽  
Cd8 T Cell ◽  
Cell Recognition ◽  
T Cell Recognition

Optimal NK Cell Expansion Depends on Accessory Cells, Synergy between Physiologic Concentrations of IL-2 and IL-15, and Umbilical Cord Blood (UCB) NK Cell Precursors Expand Better Than Adult NK Cells.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3642-3642 ◽  
Author(s):  
Purvi Gada ◽  
Michelle Gleason ◽  
Valarie McCullar ◽  
Philip B. McGlave ◽  
Jeffrey S. Miller
Keyword(s):  
T Cells ◽  
B Cells ◽  
Nk Cells ◽  
Cell Expansion ◽  
Nk Cell ◽  
High Dose ◽  
Unexpected Result ◽  
Accessory Cells

Abstract Allogeneic NK cells may play a therapeutic role in treating patients with AML. We have previously shown that high dose cyclophosphamide (120 mg/kg × 1 day) and fludarabine (125 mg/m2 × 5 days) can clear lymphoid space and induce a surge of endogenous IL-15 to expand haploidentical NK cells obtained from CD3-depleted lymphapheresis products from adult donors. In this initial study, 5 of 19 patients achieved remissions and in vivo NK cell expansion. Limitations of this therapy includeinability of NK cells to expand in most patients,development of PTLD (in one patient) andinadequate disease control.We hypothesized that contaminating T cells could compete for NK cell expansion, that B-cells may contribute to PTLD, and that a 2-step NK cell purification method using CD3 depletion followed by CD56 selection (CliniMacs) may overcome these problems. We tested this in 9 patients with advanced AML. The purified NK cells, activated with 1000 U/ml IL-2 (16–20 hours), were infused 48 hours after the last fludarabine dose. Patients then received subcutaneous IL-2 (10 MU) every other day × 6 doses to expand NK cells in vivo. None of the 9 pts treated on this protocol achieved remission or exhibited evidence of in vivo expansion. Several studies were designed to investigate this unexpected result. First, we found that the more extensive processing resulted in approximately 1/3 the NK cell recovery compared to CD3 depletion alone (38±% viable NK cells vs. 91±2% respectively). In addition, we questioned whether the contaminating B cells and monocytes that were removed in the 2-step depletion strategy had served a critical role in NK cell activation or expansion. Cytotoxicity assays performed against K562 targets showed that the killing was about 3-fold higher with the purified (CD3-CD56+) product compared the CD3-depleted product alone (P=0.001 at E:T of 6.6:1). Proliferation, measured by a 6-day thymidine assay, was higher in proportion to the higher NK cell content. The only difference between the two NK products was their expansion after 14 days of culture, where the CD3-depleted product, with contaminating B-cells and monocytes, gave rise to greater NK cell expansion (14 ±3-fold) compared to the 2-step purified product (4.5±0.9, n=6, P=0.005). If this finding holds true in vivo, the co-infusion of accessory cells may be required for NK cell expansion. We next developed in vitro assays using very low concentrations (0.5 ng/ml) of IL-2 and IL-15 to understand their role in expansion. IL-2 or IL-15 alone induced low proliferation and the combination was synergistic. Lastly, UCB, a rich source of NK cell precursors, was compared to adult NK cells. In a short term proliferation assay, CD56+ NK cells stimulated with IL-2 + IL-15 expanded better from adult donors (61274±12999, n=6) than from UCB (20827± 6959, n=5, P=0.026) but there was no difference after 14 days in expansion culture suggesting that the only difference is in kinetics. However, UCB depleted of T-cells (enriching for NK cell precursors) exhibited higher fold expansion over 14 days under different culture conditions conducive to NK cell progenitors. In conclusion, NK cell expansion in vitro depends on cell source, IL-2 and IL-15 (increased in vivo after lymphoid depleting chemotherapy) as well as accessory cells. The role of these factors to enhance in vivo expansion is under clinical investigation to further exploit the NK cell alloreactivity against AML targets.

Effective Prevention of Acute Graft-Verses-Host Disease by Targeting PKC Alpha and PKC Theta in Mice

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1898-1898
Author(s):  
Kelley M.K. Haarberg ◽  
Crystina Bronk ◽  
Dapeng Wang ◽  
Amer Beg ◽  
Xue-Zhong Yu
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
Acute Gvhd ◽  
T Cell Signaling ◽  
Effector Cells ◽  
T Effector Cells ◽  
Immunologic Synapse

Abstract Abstract 1898 Protein kinase C theta (PKCθ), a T cell signaling molecule, has been implicated as a therapeutic target for several autoimmune diseases as well as graft-versus-host disease (GVHD). PKCθ plays a vital role in stabilization of the immunologic synapse between T effector cells and antigen presenting cells (APC), but has been shown to be excluded from the immunologic synapse in T regulatory cells (T reg). PKCθ inhibition reduces the alloreactivity of donor T cells responsible for induction of GVHD while preserving graft-versus-leukemia (GVL) responses. The roles of PKCθ and the potential compensatory alpha isoform (PKCα) are not clearly defined with regard to alloresponses or T cell mediated responses in GVHD. In this context, we measured PKCθ and PKCα/θ gene deficient T cell activation upon TCR-ligation in vitro using [3H]-TdR incorporation and CSFE labeling assays. T cells from PKCθ and PKCα/θ gene deficient donor mice were utilized in vivo in a pre-clinical allogenic murine model of myeloablative bone marrow transplantation (BMT). The development of GVHD was monitored in recipient mice with or without injection of A20-luciferase cells to observe the progression of GVL in vivo. Combined blockade of PKCα and PKCθ causes a significant decrease in T cell proliferation compared to blocking PKCθ alone in vitro. Deficiency in PKCα and PKCθ had no effect on immune reconstitution following irradiation and BMT in vivo. Even with a high transplant load of 5×106 CD4+ and CD8+ T cells, PKCα/θ deficient (PKCα/θ−/−) T cells failed to induce acute GVHD. Our data suggest that the ability of double deficient T cells to induce GVHD was further reduced than PKCθ-deficient T cells. Additionally, a greater number and percentage of B220+ B cells and FoxP3+ T regs were isolated from the spleens of PKCα/θ−/− T cell recipient mice 120 after BMT than were isolated from wild type (WT) or PKCθ−/− T cell recipients. Fewer CD4+ or CD8+ T effector cells were isolated from the spleens of PKCα/θ−/− T cell recipient mice 120 after BMT than were isolated from wild type or PKCθ−/− T cell recipients. Importantly, the activity of B cells isolated from PKCα/θ−/− T cell recipient mice 120 after BMT was greater on a per cell basis, while the activity of T effector cells isolated from these mice was greatly reduced compared to WT or PKCθ−/− T cell recipients. While not absent, GVL was reduced in PKCα/θ−/− T cell recipient mice when compared to WT or PKCθ−/− T cell recipients. This work demonstrates the requirement of PKCα and θ for optimal activation and function of T cells in vitro. These experiments highlight a potential compensatory role for PKCα in the absence of PKCθ in T cell signaling and activation. Combined deficiency of PKCα and θ prevents induction of acute GVHD while improving the maintenance of splenic cellularity in PKCα/θ T cell recipient mice. Additionally, PKCα/θ dual deficient T cell transplant shifts the splenic balance toward a greater number and percentage of T reg and B cells and away from T effector cells following BMT. The reduced and sub-optimally active T effector cells isolated from PKCα/θ−/− T cell recipient mice in combination with reduced GVL stresses the importance of PKCα and θ molecules and their roles in T cell activity in the context of both GVHD and GVL. Dual deficiency of PKCα/θ is associated with a decline of T effector function that is optimal for the amelioration of GVHD, but is perhaps too reduced to substantially maintain effective GVL. Modulation of PKCα and θ signaling presents a valid avenue of investigation as a therapeutic option for GVHD. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Role of the major histocompatibility complex in T cell activation of B cell subpopulations. Major histocompatibility complex-restricted and -unrestricted B cell responses are mediated by distinct B cell subpopulations

1981 ◽  
Vol 154 (4) ◽  
pp. 1100-1115 ◽  
Author(s):  
Y Asano ◽  
A Singer ◽  
RJ Hodes
Keyword(s):  
T Cells ◽  
Major Histocompatibility Complex ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Recognition ◽  
Major Histocompatibility ◽  
T Cell Recognition ◽  
Histocompatibility Complex ◽  
Cell Subpopulations

The present study has evaluated the identity of the B cell subpopulations participating in T dependent antibody responses that differ in their requirements for major histocompatibility complex-restricted T cell recognition. In vitro responses of keyhole limpet hemocyanin (KLH)-primed T cells and trinitrophenyl (TNP)-primed B cells were studied to both low and high concentrations of the antigen TNP-KLH. It was first demonstrated that for responses to low concentrations of TNP-KLH, (A × B)F(1) {arrow} parent(A) chimeric helper T cells were restricted in their ability to recognize parent(A) but not parent(B) H-2 determinants expressed by both B cells and antigen-presenting cells (APC). In contrast, at higher antigen concentrations, helper T cells were not restricted in their interaction with B cells. It was then determined whether these observed differences in T cell recognition resulted from the activation of distinct B cell subpopulations with different activation requirements. At low concentrations of TNP-KLH it was demonstrated that Lyb-5(-) B cells were activated, and that it was thus the activation of the Lyb-5(-) subpopulation that required T cell recognition of B cell H-2 under these conditions. In contrast, responses to high concentration of antigen required the participation of Lyb-5(+) B cells, and these Lyb-5(+) B cells were activated by a pathway that required H-2- restricted T cell interaction with APC, but not with B cells. The findings presented here have demonstrated that Lyb-5(-) and Lyb-5(+) B cells constitute B cell subpopulations that differ significantly in their activation requirements for T cell-dependent antibody responses to TNP-KLH. In so doing, these findings have established that the function of genetic restrictions in immune response regulation is critically dependent upon the activation pathways employed by functionally distinct subpopulations of B, as well as T, lymphocytes.

scholarly journals Immunoglobulin signal transduction guides the specificity of B cell-T cell interactions and is blocked in tolerant self-reactive B cells.

1994 ◽  
Vol 179 (2) ◽  
pp. 425-438 ◽  
Author(s):  
M P Cooke ◽  
A W Heath ◽  
K M Shokat ◽  
Y Zeng ◽  
F D Finkelman ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
Transgenic Mice ◽  
B Lymphocytes ◽  
Molecular Mechanisms ◽  
Interleukin 4 ◽  
Th Cells

The specificity of antibody (Ab) responses depends on focusing helper T (Th) lymphocyte signals to suitable B lymphocytes capable of binding foreign antigens (Ags), and away from nonspecific or self-reactive B cells. To investigate the molecular mechanisms that prevent the activation of self-reactive B lymphocytes, the activation requirements of B cells specific for the Ag hen egg lysozyme (HEL) obtained from immunoglobulin (Ig)-transgenic mice were compared with those of functionally tolerant B cells isolated from Ig-transgenic mice which also express soluble HEL. To eliminate the need for surface (s)Ig-mediated Ag uptake and presentation and allow the effects of sIg signaling to be studied in isolation, we assessed the ability of allogeneic T cells from bm12 strain mice to provide in vivo help to C57BL/6 strain-transgenic B cells. Interestingly, non-tolerant Ig-transgenic B cells required both allogeneic Th cells and binding of soluble HEL for efficient activation and Ab production. By contrast, tolerant self-reactive B cells from Ig/HEL double transgenic mice responded poorly to the same combination of allogeneic T cells and soluble HEL. The tolerant B cells were nevertheless normally responsive to stimulation with interleukin 4 and anti-CD40 Abs in vitro, suggesting that they retained the capacity to respond to mediators of T cell help. However, the tolerant B cells exhibited a proximal block in the sIg signaling pathway which prevented activation of receptor-associated tyrosine kinases in response to the binding of soluble HEL. The functional significance of this sIg signaling defect was confirmed by using a more potent membrane-bound form of HEL capable of triggering sIg signaling in tolerant B cells, which markedly restored their ability to collaborate with allogeneic Th cells and produce Ab. These findings indicate that Ag-specific B cells require two signals for mounting a T cell-dependent Ab response and identify regulation of sIg signaling as a mechanism for controlling self-reactive B cells.

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