|
||
Articles |
| Abstract |
|---|
|
|
|---|
Memory B lymphocytes are mainly generated in the germinal centers (GCs)1 of secondary lymphoid organs (1–8). Within these structures, proliferating B blasts can increase the affinity of their surface Igs through somatic mutation of their Ig variable region genes and positive selection of high affinity mutants (9–16). Isotype switch of the Igs can also occur during GC reaction (17–19). After leaving the GCs, memory B cells either join the recirculating pool of lymphocytes, or home to antigen draining sites such as the marginal zone of the spleen (20). Memory B cells display several intrinsic differences with naive B cells: (a) lower threshold for activation, (b) ability to directly present antigen to helper T cells, and (c) longer life span (21–27). Although these features of memory B cells are essential for the immune system to make a robust secondary antibody response, they may lead to an overexpansion of a particular memory B cell clone, which would overload the immune system during chronic infections or antigenic stimulations (26). Several hypotheses can be put forward to explain how the immune system controls the size of memory cell clones: (a) decreasing potential hypothesis: memory (T and B) cells generated after each round of stimulation acquire a decreased potential to generate new memory cells and an increased potential to undergo terminal differentiation into effector cells (26, 27), (b) growth factor/costimulatory signal starvation hypothesis: at the late stage of immune responses, the clonally expanded memory blasts (T and B) undergo apoptosis in the absence of growth factors/ costimulating molecules (26, 27), and (c) hypothesis of Fas ligand–mediated apoptosis: T cells can undergo autocrine Fas ligand–mediated apoptosis (28–30), and B cells can be sensitized to Fas ligand–mediated apoptosis by CD40 triggering (31).
Recently, large amounts of human memory B cells have been purified from human tonsils and blood, based on their IgD–CD38– or IgM+IgD– or IgA1+ phenotypes (32–36). These cells contained somatically mutated IgV genes, an indication of their germinal center origin. The isolation of these memory B cells allowed us to directly test the decreasing potential hypothesis by culturing memory and naive B cells in vitro. Herein, we describe a novel important feature of memory B cells: their bias towards terminal plasma cell differentiation.
Recombinant human IL-2 was purchased from Amgen Biologicals (Thousand Oaks, CA) and recombinant human IL-10 is from Schering-Plough Research Institute (Kenilworth, NJ). IL-2 was used at 10 U/ml and IL-10 at 100 ng/ml in cultures.
Giemsa-Gurr and Mayer's hematoxylin staining solutions were purchased from BDH Laboratory Supplies (Poole, England) and Sigma Chemical Co., respectively.
Purification of B Cell Populations.
Proliferation Assays.
Two-step Cell Cultures.
Quantitation of CD40L Molecules on Murine Fibroblasts. The number of CD40L molecules expressed on transfected fibroblasts was estimated using a Qifikit® system (Dako, Goldstrup, Denmark) immediately before establishment of cultures. In brief, cells were incubated at saturation with either an anti-CD40L mAb (IgG1 isotype) or a nonrelevant control-matched antibody for 20 min on ice. After two washes, they were incubated with FITC-conjugated sheep anti–mouse immunoglobulins at the same time as different beads suspensions, coated with a known number of mouse Igs. Cells and beads were then analyzed using a FACScan® (Becton Dickinson, Sunnyvale, CA). Means of fluorescence intensity were then plotted against the number of mouse Igs on beads and linear regression was calculated (r2
Cell Cultures with Progressive Triggering of CD40.
Ig Secretion Assays.
Cell Sorting.
Giemsa and Immunoenzymatic Stainings.
![]()
Materials and Methods
Top
Abstract
Materials and Methods
Results
Discussion
References
Antibodies and Reagents.
The mouse mAbs used for the phenotypic studies were FITC-conjugated anti-CD20 (IOB20; Immunotech, Marseille, France) and PE-conjugated anti-CD38 (Leu17; Becton Dickinson Monoclonal Center, Mountain View, CA). Antibodies used for cell purification and cell culture were anti-CD4 (Q4120) and biotinylated anti-IgD (HJ9) purchased from Sigma Chemical Co. (St. Louis, MO), anti-CD38 (T16), anti-Ig
(6E1), and anti-Ig
(C4) purchased from Immunotech, and anti-CD2, -CD3, -CD8 ascites produced in our own laboratory using the OKT hybridomas obtained from American Type Culture Collection (Rockville, MD). Antibodies used for immunoenzymatic stainings are described in the corresponding section. Anti-CD40 ligand (LL48) -blocking mAb and CD40 ligand (CD40L) -transfected murine fibroblasts were produced in our laboratory (31).
Naive and memory B cells were purified from human tonsils obtained from children undergoing routine tonsillectomy, as previously described (33). In brief, tonsils were finely minced in RPMI 1640 (GIBCO BRL, Paisley, UK). Cell suspension was washed twice and T cells were depleted by sheep RBC rosetting and centrifugation at room temperature on ditrizoate-ficoll (density = 1,077; Eurobio, Les Ulis, France). B cells were then incubated with biotinylated anti–human IgD antibodies. For naive cell purification, two rounds of positive selection were performed with a magnetic activated cell sorter (MACS®; Miltenyi Biotec, Bergisch Gladbach, Germany). For memory cell preparation, two rounds of negative magnetic beads depletion (Streptavidin-coated Dynabeads; Dynal, Oslo, Norway) were performed. Both resulting IgD+ and IgD– populations were further depleted of T cells and CD38+ (i.e., GC) B cells by incubation with anti-CD2, -CD3, -CD4, -CD8, and -CD38 antibodies followed by two rounds of depletion with anti–mouse IgG-coated magnetic beads (Dynal). This procedure lead to 98–99.5% pure naive and 95–99.5% pure memory B cell populations.
For DNA synthesis, 2.5 x 104 B cells were cultured together with 5 x 103, 75 Gy–irradiated, CD40L– transfected fibroblasts in 200 µl Iscove medium (GIBCO) complemented with 5% FCS (GIBCO) for 12 d in the presence of IL-2 and IL-10. DNA synthesis was assessed by incubation with 1 µCi of tritiated thymidine (Amersham, Les Ulis, France) during the last 8 h of culture. For cellular expansion, 1.5 x 105 B cells were cultured with 5 x 104 CD40L–transfected fibroblasts for 12 d in the presence of IL-2 and IL-10. Cells were harvested and counted in tripan blue (GIBCO) to exclude dead cells.
1.5–2 x 107 purified naive or memory B cells were cultured for 3 d in 20 ml Iscove medium complemented with 5% FCS in the presence of IL-2, IL-10, and CD40L–transfected fibroblasts (5:1, B cells/fibroblast). Cells were then harvested, washed, and recultured with or without CD40L. In another set of experiments, anti-Ig
and Ig
antibodies were used to trigger B cell receptor (BCR) at 2 µg/ml final concentration. Secondary cultures consisted of 1.5 x 105 B cells in 1 ml Iscove medium containing IL-2 and IL-10, together with 5 x 104 irradiated murine fibroblasts. Murine fibroblasts were either CD40L–transfected cells or nontransfected cells together with anti-CD40L–blocking antibody at 2 µg/ml to block the signals given by CD40L–transfected cells that could have been harvested from the primary cultures. All secondary cultures were done in triplicate. After 4 d, cultures were harvested, supernatants frozen for antibody titer assays, and cells kept for analysis.
0.998 in all experiments). The number of recognized molecules (CD40L) on stained fibroblasts was calculated using the linear regression and the fluorescence intensity of these cells, after taking account of the fluorescence of the cells stained with the control-matched antibody.
To assess the effect of progressive triggering of CD40 antigen on naive and memory B cells, a second two-step culture was established. Cells were grown in primary cultures as in the previous two-step culture system. After 3 d, cells were recultured under seven different conditions. As the number of CD40L molecules on transfected fibroblasts varies from one experiment to another, a fixed cell ratio, rather than a fixed number of molecules, was chosen to avoid differences in the fibroblast feeder effects. Therefore, 1.5 x 105 B cells were cultured for 4 d in 1 ml Iscove medium containing IL-2 and IL-10, together with 5 x 104 irradiated fibroblasts. One culture condition was established with CD40L-transfected cells whose CD40L molecules number has been determined. These cells are then diluted with nontransfected irradiated fibroblasts for other culture conditions at the ratios of 1/2, 1/4, 1/8, and 1/16. Two other cultures were also set using parental cells, with or without anti-CD40L antibody at 2 µg/ml. All secondary cultures were set in triplicates and designed as the number of CD40L molecules present in the culture per B cell.
IgA, IgG, and IgM concentrations in culture supernatants were measured using ELISA. Total Ig levels are given as the summation of these values.
Naive and memory cells were cultured for 3 d in the presence of IL-2, IL-10, and CD40L-transfected fibroblasts. They were then harvested and recultured for an additional 4 d with IL-2, IL-10, and parental fibroblasts. After harvesting, debris and dead cells were depleted from the cultures by centrifugation on ditrizoate-ficoll (Eurobio). Cells were then stained with FITC-conjugated anti-CD20 and PE-conjugated anti-CD38 antibodies. Both CD20–/lowCD38high and CD20+CD38– populations were sorted using a FACStar® (Becton Dickinson Immunocytometry Systems, San Jose, CA).
7 x 104 sorted cells were cytocentrifuged on microscope slides. Some slides were stained with Giemsa-Gurr solution, whereas others were kept for immunoenzymatic staining. Human Igs were revealed by anti– human
and
light chain antibodies (A8B5 and N10/2 clones, respectively, IgG1 isotypes; Dako), whereas IgM isotype Igs were revealed by anti–human IgM mAb (145-8, IgG1 isotype; Becton Dickinson Monoclonal Center). Enzymatic activity was developed with Fast Red substrate (Dako). All immunoenzymatically colored slides were lightly counterstained with Mayer's hematoxylin solution.
![]()
Results
Top
Abstract
Materials and Methods
Results
Discussion
References
Memory B Cells Undergo Prompt Differentiation into Plasma Cells upon Activation.
Using a two-step culture system, we previously demonstrated that continuous triggering of CD40 antigen on GC cells inhibits their terminal differentiation into plasma cells (PC; 37). To determine the influence of CD40L on the capacity of memory and naive B cells to generate PCs, similar culture conditions were used. Both populations were cultured for 3 d over CD40L-transfected fibroblasts in the presence of IL-2 and IL-10. Activated B cell blasts were then recultured for 4 d with nontransfected fibroblasts, IL-2, IL-10, and an anti-CD40L–blocking antibody to block the CD40L-transfected fibroblasts carried over from the primary culture. Although naive B cells yielded 16.4 ± 6.6% CD20–/lowCD38high plasma cells (mean ± SD, n = 7; Fig. 1 B; Table 1), memory B cells yielded 62.4 ± 11.9% plasma cells (mean ± SD, n = 4; Fig. 1 D; Table 1). Accordingly, naive B cells yielded three times more nondifferentiated CD20+CD38low B blasts than did memory cells. Addition of CD40L during the secondary culture (Fig. 1, A and C) considerably inhibited the plasma cell differentiation of B cell blasts, generated from both naive and memory cells (Table 1).
|
|
and Ig
light chain staining (Fig. 2 C). In contrast, CD20+CD38low populations display the morphology of blasts with a weak surface Ig expression (Fig. 2, B and D). Although 50% of plasma cells generated from naive B cells contain intracytoplasmic IgM (Fig. 2 E), only 20% of plasma cells generated from memory B cells expressed IgM (Fig. 2 F).
|
|
|
|
and 2 µg/ml of anti-Ig
antibodies were added into the cultures in the presence of CD40L, IL-2, and IL-10. At the end of the culture, cells were washed and seeded in a 4 d secondary culture with IL-2, IL-10, and different concentrations of CD40L. Fig. 6 shows that in the presence of three different CD40L concentrations (9.6 x 104/cell, 4.8 x 104/cell, no CD40L), 3, 6, and 13% of CD38+ CD20– plasma cells were generated from the naive B cells. In the same culture conditions, 21, 29, and 43% of CD38+ CD20– plasma cells were generated from the memory B cells. This experiment indicates that memory B cells, but not naive B cells, preferentially undergo plasma cell differentiation even after BCR triggering.
|
| Discussion |
|---|
|
|
|---|
|
Although CD40L inhibits the PC differentiation of naive, GC, and memory B cells, a fraction of the memory cell subset seems to be resistant to this effect. Differential effects of CD40L on mature B cell subsets have already been noticed. For instance, CD40 triggering is an important survival but a minor proliferative signal for GC cells (55–57), whereas it provides a strong and long-term proliferative signal to resting naive and memory B cells (58–61). The molecular mechanisms underlying the propensity of memory B cells to undergo terminal differentiation are still unknown. CD40 triggering on human GCs and resting mature B cells results in the activation of different protein kinases (62, 63). Further comparative studies of CD40 signaling pathways in naive, GC, and memory B cells should now be carried on to explain how mature B cells change their responses to CD40 triggering at different stages of their immunopoiesis.
| Acknowledgments |
|---|
Submitted: 30 December 1996
Revised: 3 July 1997
1 Abbreviations used in this paper: BCR, B cell receptor; CD40L, CD40 ligand; GC, germinal center; PC, plasma cell.
| References |
|---|
|
|
|---|
1 Kroese, F.G.M., W. Timens, and P. Nieuwenhuis. 1990. Germinal center reaction and B lymphocytes: morphology and function. In Current Topics in Pathology. Reaction Pattern of the Lymph Node. Springer Verlag, Berlin. 103–148.
2 Liu YJ, Johnson GD, Gordon J & MacLennan ICM. Germinal centers in T-cell–dependent antibody responses, Immunol Today, 1992, 13, 17–21.[Medline]
3 Nossal GJV. The molecular and cellular basis of affinity maturation in the antibody response, Cell, 1992, 68, 1–3.[Medline]
4 Gray D. Immunological memory, Annu Rev Immunol, 1993, 11, 49–77.[Medline]
5 MacLennan ICM. Germinal centers, Annu Rev Immunol, 1994, 12, 117–139.[Medline]
6 Weissman IL. Developmental switches in the immune system, Cell, 1994, 76, 207–218.[Medline]
7 Kelsoe G. In situ studies of the germinal center reaction, Adv Immunol, 1995, 60, 267–288.[Medline]
8 Thorbecke GJ, Amin AR & Tsiagbe VK. Biology of germinal centers in lymphoid tissue, FASEB J, 1994, 8, 832–840.[Abstract]
9 Manser T, Wysocki LJ, Gridley T, Near RI & Gefter ML. The molecular evolution of the immune response, Immunol Today, 1985, 6, 94–101.
10 Berek C, Berger A & Apel M. Maturation of the immune response in germinal centers, Cell, 1991, 67, 1121–1129.[Medline]
11 Jacob J, Kelsoe G, Rajewsky K & Weiss U. Intraclonal generation of antibody mutants in germinal centres, Nature (Lond), 1991, 354, 389–392.[Medline]
12 Küppers R, Zhao M, Hansmann M-L & Rajewsky K. Tracing B cell development in human germinal centres by molecular analysis of single cells picked from histological sections, EMBO (Eur Mol Biol Organ) J, 1993, 12, 4955–4967.[Medline]
13 McHeyzer-Williams MG, McLean MJ, Lalor PA & Nossal GJV. Antigen-driven B cell differentiation in vivo, J Exp Med, 1993, 178, 295–307.
14 Klein U, Küppers R & Rajewsky K. Variable region gene analysis of B cell subsets derived from a 4-year-old child: somatically mutated memory B cells accumulate in the peripheral blood already at young age, J Exp Med, 1994, 180, 1383–1393.
15 Pascual V, Liu YJ, Magalski A, de Bouteiller O, Banchereau J & Capra JD. Analysis of somatic mutation in five B cell subsets of human tonsil, J Exp Med, 1994, 180, 329–339.
16 Rajewsky K. Clonal selection and learning in the antibody system, Nature (Lond), 1996, 381, 751–758.[Medline]
17 Kraal G, Weissman IL & Butcher EC. Germinal centre B cells: antigen specificity and charges in heavy chain class expression, Nature (Lond), 1982, 298, 377–379.[Medline]
18 Liu YJ, Malisan F, de Bouteiller O, Guret C, Lebecque S, Banchereau J, Mills FC, Max EE & Martinez-Valdez H. Within germinal centers isotype switching of immunoglobulin genes occurs after onset of somatic mutation, Immunity, 1996, 4, 241–250.[Medline]
19 Toellner KM, Gulbranson-Judge A, Taylor DR, Man-Yuen D & MacLennan ICM. Immunoglobulin switch transcript production in vivo related to the site and time of antigen-specific B cell activation, J Exp Med, 1996, 183, 2303–2312.
20 Liu Y-J, Oldfield S & MacLennan ICM. Memory B cells in T cell–dependent antibody responses colonize the splenic marginal zones, Eur J Immunol, 1988, 18, 355–362.[Medline]
21 MacLennan ICM & Gray D. Antigen-driven selection of virgin and memory B cells, Immunol Rev, 1986, 91, 61–85.[Medline]
22 Rajewsky, K. 1989. Evolutionary and somatic immunological memory. In Progress in Immunology, VII. F. Melchers, editor. Springer Verlag, Berlin. 397–403.
23 Gray D & Sprent J. Immunological memory, Curr Top Microbiol Immunol, 1990, 159, V–VII.
24 Vitetta ES, Berton MT, Burger C, Kepron M, Lee WT & Yin XM. Memory B and T cells, Annu Rev Immunol, 1991, 9, 193–217.[Medline]
25 Mackay CR. Immunological memory, Adv Immunol, 1993, 53, 217–265.[Medline]
26 Sprent J. T and B memory cells, Cell, 1994, 76, 315–322.[Medline]
27 Ahmed R & Gray D. Immunological memory and protective immunity: understanding their relation, Science (Wash DC), 1996, 272, 54–60.[Abstract]
28 Brunner T, Mogil RJ, LaFace D, Yoo NJ, Mahboubi A, Echeverri F, Martin SJ, Force WR, Lynch DH, Ware CF & Green DR. Cell-autonomous Fas (CD95)/ Fas-ligand interaction mediates activation-induced apoptosis in T-cell hybridomas, Nature (Lond), 1995, 373, 441–444.[Medline]
29 Dhein J, Walczak H, Bäumler C, Debatin K-M & Krammer PH. Autocrine T-cell suicide mediated by APO-1(Fas/CD95), Nature (Lond), 1995, 373, 438–441.[Medline]
30 Ju S-T, Panka DJ, Cui H, Ettinger R, El-Khatib M, Sherr DH, Stanger BZ & Marshak-Rothstein A. Fas (CD95)/FasL interactions required for programmed cell death after T-cell activation, Nature (Lond), 1995, 373, 444–448.[Medline]
31 Garrone P, Neidhardt EM, Garcia E, Galibert L, van Kooten C & Banchereau J. Fas ligation induces apoptosis of CD40-activated human B lymphocytes, J Exp Med, 1995, 182, 1265–1273.
32 Lagresle C, Bella C & Defrance T. Phenotypic and functional heterogeneity of the IgD–B cell compartment: identification of two major tonsillar B cell subsets, Int Immunol, 1993, 5, 1259–1268.
33 Liu YJ, Barthélémy C, de Bouteiller O, Arpin C, Durand I & Banchereau J. Memory B cells from human tonsils colonize mucosal epithelium and directly present antigen to T cells by rapid upregulation of B7.1 and B7.2, Immunity, 1995, 2, 238–248.
34 Casamayor-Palleja M, Feuillard J, Ball J, Drew M & MacLennan ICM. Centrocytes rapidly adopt a memory B cell phenotype on co-culture with autologous germinal centre T cell–enriched preparations, Int Immunol, 1996, 8, 737–744.
35 Irsch J, Irlenbusch S, Radl J, Burrows PD, Cooper MD & Radbruch AH. Switch recombination in normal IgA1+B lymphocytes, Proc Natl Acad Sci USA, 1994, 91, 1323–1327.
36 Klein U, Küppers R & Rajewsky K. Evidence for a large compartment of IgM-expressing memory B cells in humans, Blood, 1997, 89, 1288–1298.
37 Arpin C, Déchanet J, van Kooten C, Merville P, Grouard G, Brière F, Banchereau J & Liu YJ. Generation of memory B cells and plasma cells in vitro, Science (Wash DC), 1995, 268, 720–722.
38 Lawton AR, Asofsky R, Hylton MB & Cooper MD. Suppression of immunoglobulin class synthesis in mice. I. Effects of treatment with antibody to µ-chain, J Exp Med, 1972, 135, 277–282.[Abstract]
39 Kroese FGM, Seijen HG & Nieuwenhuis P. The initiation of germinal centre reactivity, Res Immunol, 1991, 142, 249–252.[Medline]
40 Liu Y-J, Zhang J, Lane PJL, Chan EY-T & MacLennan ICM. Sites of specific B cell activation in primary and secondary responses to T cell–dependent and T cell–independent antigens, Eur J Immunol, 1991, 21, 2951–2962.[Medline]
41 Cebra JJ, Schrader CE, Shroff KE & Weinstein PD. Are Peyer's patch germinal centre reactions different from those occuring in other lymphoid tissues? , Res Immunol, 1991, 142, 222–226.[Medline]
42 Benner R, Hijmans W & Haaijman JJ. The bone marrow: the major source of serum immunoglobulins, but still a neglected site of antibody formation, Clin Exp Immunol, 1981, 46, 1–8.[Medline]
43 Ho F, Lortan JE, MacLennan ICM & Khan M. Distinct short-lived and long-lived antibody-producing cell populations, Eur J Immunol, 1986, 16, 1297–1301.[Medline]
44 Merville P, Dechanet J, Desmoulière A, Durand I, de Bouteiller O, Garrone P, Banchereau J & Liu YJ. Bcl-2 positive tonsillar plasma cells are rescued from prompt apoptosis by bone marrow fibroblasts, J Exp Med, 1996, 183, 227–236.
45 Webb S, Morris C & Sprent J. Extrathymic tolerance of mature T cells: clonal elimination as a consequence of immunity, Cell, 1990, 63, 1249–1256.[Medline]
46 Rocha B & von Boehmer H. Peripheral selection of the T cell repertoire, Science (Wash DC), 1991, 251, 1225–1228.
47 Moskophidis D, Lechner F, Pircher H & Zinkernagel RM. Virus persistence in acutely immunocompetent mice by exhaustion of antiviral cytotoxic effector T cells (erratum published 364:262), Nature (Lond), 1993, 362, 758–761.[Medline]
48 Webb SR & Sprent J. Factors controlling the reactivity of immature and mature T cells to Mls antigens in vivo, Immunol Rev, 1993, 131, 169–188.[Medline]
49 Callard RE, Herbert J, Smith SH, Armitage RJ & Costelloe KE. CD40 cross-linking inhibits specific antibody production by human B cells, Int Immunol, 1995, 7, 1809–1815.
50 Lane P, Burdet C, McConnell F, Lanzavecchia A & Padovan E. CD40 ligand-independent B cell activation revealed by CD40 ligand-deficient T cell clones: evidence for distinct activation requirements for antibody formation and B cell proliferation, Eur J Immunol, 1995, 25, 1788–1793.[Medline]
51 Noelle RJ. CD40 and its ligand in host defense, Immunity, 1996, 4, 415–419.[Medline]
52 Lederman S, Yellin MJ, Inghirami G, Lee JJ, Knowles DM & Chess L. Molecular interactions mediating T–B lymphocyte collaboration in human lymphoid follicles. Roles of T cell–B cell–activating molecule (5c8 antigen) and CD40 in contact-dependent help, J Immunol, 1992, 149, 3817–3826.[Abstract]
53 van den Eetwegh AJM, Noëlle RJ, Roy M, Shepherd DM, Aruffo A, Ledbetter JA, Boersma WJA & Claassen E. In vivo CD40–gp39 interactions are essential for thymus-dependent humoral immunity. I. In vivo expression of CD40 ligand, cytokines, and antibody production delineates sites of cognate T–B cell interactions, J Exp Med, 1993, 178, 1555–1565.
54 Casamayor-Palleja M, Khan M & MacLennan ICM. A subset of CD4+memory T cells contains preformed CD40 ligand that is rapidly but transiently expressed on their surface after activation through the T cell receptor complex, J Exp Med, 1995, 181, 1293–1301.
55 Liu YJ, Joshua DE, Williams GT, Smith CA, Gordon J & MacLennan ICM. Mechanisms of antigen-driven selection in germinal centers, Nature (Lond), 1989, 342, 929–931.[Medline]
56 Holder MJ, Wang H, Milner AE, Casamayor M, Armitage R, Spriggs MK, Fanslow WC, MacLennan ICM, Gregory CD & Gordon J. Suppression of apoptosis in normal and neoplastic human B lymphocytes by CD40 ligand is independent of Bcl-2 induction, Eur J Immunol, 1993, 23, 2368–2371.[Medline]
57 Gray D, Siepmann K, van Essen D, Poudrier J, Wykes M, Jainandunsing S, Bergthorsdottir S & Dullforce P. B–T lymphocyte interactions in the generation and survival of memory cells, Immunol Rev, 1996, 150, 45–61.[Medline]
58 Clark EA & Ledbetter JA. Activation of human B cells mediated through two distinct cell surface differentiation antigens, Bp35 and Bp50, Proc Natl Acad Sci USA, 1986, 83, 4494–4498.
59 Gordon J, Millsum MJ, Guy GR & Ledbetter JA. Synergistic interaction between interleukin 4 and anti-Bp50 (CDw40) revealed in a novel B cell restimulation assay, Eur J Immunol, 1987, 17, 1535–1538.[Medline]
60 Spriggs MK, Armitage RJ, Strockbine L, Clifford KN, Macduff BM, Sato TA, Maliszewski CR & Fanslow WC. Recombinant human CD40 ligand stimulates B cell proliferation and immunoglobulin E secretion, J Exp Med, 1992, 176, 1543–1550.
61 Banchereau J, Bazan F, Blanchard D, Brière F, Galizzi JP, van Kooten C, Liu YJ, Rousset F & Saeland S. The CD40 antigen and its Ligand, Annu Rev Immunol, 1994, 12, 881–922.[Medline]
62 Uckun FM, Schieven GL, Dibirdik I, Chandan-Langlie M, Tuel-Ahlgren L & Ledbetter JA. Stimulation of protein tyrosine phosphorylation, phosphoinositide turnover, and multiple previously unidentified serine/threonine-specific protein kinases by the pan–B-cell receptor CD40/ Bp50 at discrete developmental stages of human B-cell ontogeny, J Biol Chem, 1991, 266, 17478–17485.
63 Knox KA & Gordon J. Protein tyrosine phosphorylation is mandatory for CD40-mediated rescue of germinal center B cells from apoptosis, Eur J Immunol, 1993, 23, 2578–2584.[Medline]
This article has been cited by other articles:
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| TABLE OF CONTENTS |
|