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G J Thorbecke

Publications and source records attributed to G J Thorbecke.

At least 37 records · Page 2Linked to original sources
PubMed1996

Reconstitution of germinal center formation in nude mice with Th1 and Th2 clones.

We investigated the ability of hemocyanin (KLH)-specific cloned CD4+ T cells expressing defined cytokine profiles to support germinal center (GC) formation in syngeneic athymic recipients in response to hapten-KLH challenge. Th1 clones producing IL-2 and IFN-gamma did not by themselves increase GC production above background, while Th2 cells producing IL-4 and IL-5 did. However, the combination of Th1 and Th2 cytokines was more effective than Th2 cytokines alone, suggesting a synergistic effect in this aspect of their help for B cells. In contrast to GC formation, antibody production could be induced with Th1 or Th2 clones given separately (Th1 clones inducing IgG2a, and Th2 clones inducing IgG1 and IgE). These results indicate that the T cell requirements for GC production are different from those for isotype switching and Ig secretion. It is postulated that the synergy between Th1 and Th2 cells in the induction of GC formation reflects the synergy between Th1 and Th2 cytokines, such as IFN-gamma and IL-5, in promotion of GC cell proliferation.

Adoptive Transfer↗
PubMed1996

Administration of interleukin-10 at the time of priming protects Corynebacterium parvum-primed mice against LPS- and TNF-alpha-induced lethality.

Several laboratories have described the protective effects of interleukin-10 (IL-10) in mouse models of lethal endotoxemia. In most of these experiments, protection was observed in normal mice that were given a lethal dose of LPS. However, we failed to observe protection with IL-10 in LPS-challenged mice that had been primed with Corynebacterium parvum (Proprionibacterium acnes). We have extended our studies with IL-10 in C. parvum-primed mice and in some cases have observed protection that appears to depend on the strength of the sensitization to C. parvum. When IL-10 was administered to mice at the time of priming, it was particularly effective in blocking sensitization, as evidenced by the inability of treated mice to mount a strong inflammatory cytokine response when subsequently challenged with LPS. Following such treatment with IL-10, C. parvum-primed mice were also protected from a subsequent lethal challenge with rMuTNF-alpha. In addition, the mice were protected against LPS- and TNF-alpha-induced lethality with a single dose of an anti-TNF-alpha or anti-IFN-gamma mAb given at the time of priming. Our results suggest that TNF-alpha and IFN-gamma are produced early after priming with C. parvum and are at least partly responsible for the enhanced sensitivity of the mice to LPS and TNF-alpha. IL-10 affords protection to the mice because of its ability to block the C. parvum-induced TNF-alpha and IFN-gamma responses.

Animals↗
PubMed1996

Control of endogenous mouse mammary tumor virus superantigen expression in SJL lymphomas by a promoter within the env region.

SJL mouse lymphomas (reticulum cell sarcomas, or RCSs) of germinal center B cell origin express an endogenous mouse mammary tumor virus (mtv-29) superantigen (vSAg) that stimulates Vbeta16+ T cells to produce cytokines essential for RCS growth. Normal or LPS-activated SJL/J B cells contain two to three larger mRNAs for mouse mammary tumor virus-long terminal repeat (LTR) but not the 1.8-kb mRNA, which is prominent in RCS cells and encodes the vSAg-29. mRNAs from RCS and normal lymphoid cells were characterized by Northern hybridization using DNA probes from various regions of mtv-29, as well as by reverse transcription PCR, RNase protection, and primer extension. The larger mtv-29 transcripts, coding for envelope protein, are initiated in the 5' LTR, as expected. Surprisingly, the 1.8-kb mRNA, encoding the open reading frame of the LTR, is initiated in the middle of the env region and spliced in the 3' env. This is the first report of an mtv-vSAg transcript that is not controlled by promoter(s) located in the 5' LTR. The env initiation site appears identical to that of the mouse mammary tumor virus env transcriptional activator-directed PMA-induced defective LTR transcript in the C57BL6 T cell lymphoma, EL-4. The stimulus independence, B lymphoma specificity, and absence of deletions within either the 5' or 3' LTR regions of mtv-29 in RCS distinguish the situation in RCS cells from that in EL-4. These findings suggest that the novel mtv-29-vSAg transcript reflects an RCS-cell-specific regulation of transcription.

Animals↗
PubMed1996

Induction of inhibitory activity for B cell differentiation in human CD8 T cells with pokeweed mitogen, dimaprit, and cAMP upregulating agents: countersuppressive effect of platelet factor 4.

As shown previously, native or recombinant (r) human platelet factor 4 (PF4) alleviates the suppression induced by Con A or dimaprit, a histamine type 2 receptor (H2-R) agonist, in a murine system. The effect of rPF4 on human peripheral blood cells has now been studied, using as a model pokeweed mitogen (PWM)-induced, T-cell-mediated suppression of Ig-secreting cell (ISC) formation by Staphylococcus aureus and rIL-2 activated B cells. PWM, but not phytohemagglutinin (PHA), induced inhibitory activity in mitomycin-treated CD8+ T cells, but not unfractionated or CD4+ T cells, for both ISC formation and B cell proliferation. rPF4 and its C-terminal tridecapeptide alleviated the suppressive effect of PWM-activated CD8+ T cells on ISC production but not on proliferation. Heparin did not prevent this immunoregulatory activity of PF4. Neutralizing antibody to TGF-beta, but not to IFN-gamma or TNF-alpha, alleviated the suppression of ISC formation in some of the experiments. The H2-R appeared to play a part in inducing suppression, because the H2-R antagonist, cimetidine, prevented the PWM-induced suppression of ISC production. Furthermore, dimaprit induced suppression of ISC formation when added instead of PWM at the start of culture. Incubation of CD8+ T cells with dimaprit for only 3 hr prior to coculture with S. aureus + IL-2 activated B cells decreased the ISC response. This suppression was also alleviated by addition of rPF4 to the coculture. Similar to dimaprit, known cAMP upregulating agents, such as forskolin, dibutyryl cAMP, and cAMP analog, all induced this immunoregulatory activity in T cells. Moreover, the effect of dimaprit was prevented by the specific protein kinase A inhibitor, HA1004, suggesting strongly that upregulation of cAMP played a role in the H2-R-mediated effect. Cell contact appeared to be necessary, since supernatants from dimaprit or PWM activated T cells failed to suppress ISC production. We suggest that the known ability of PF4 to prevent TGF-beta-mediated effects on endothelial and other target cells may be involved in the alleviating effect of PF4 on the cell-contact-dependent CD8+ T-cell-mediated B cell suppression.

Amino Acid Sequence↗
PubMed1996

IgD-receptor up-regulation on human peripheral blood T cells in response to IgD in vitro or antigen in vivo correlates with the antibody response to influenza vaccination.

Aged individuals (more than 65 years) were classified as antibody (Ab) responders on the basis that they showed increases to more than or = 1:40 in serum Ab titers to all influenza virus strains present in the trivalent influenza vaccine within 4 weeks after immunization. The peripheral blood mononuclear cells (PBMC) from pre-immunization samples of blood taken from seven Ab-responders and seven Ab-nonresponders were examined for their ability to exhibit up-regulation of IgD-receptor (IgD-R) after exposure for 2 h to immobilized cross-linked IgD, as shown by rosetting with IgD-coated ox erythrocytes. The responsiveness to IgD was found to be predictive of the ability to produce Ab responses to viral protein Ag: the IgD-R up-regulation was greater than 5% in all Ab-responders and less than 4% in all the Ab-nonresponders. In addition, there was an excellent correlation between mean Ab titers (to the three viruses in sera collected 4 weeks after immunization) and the percentage of IgD-R+ cells obtained in response to IgD in PBMC from the same individual prior to immunization: p = 0.894. Injection of influenza vaccine itself also induced IgD-R on PBMC in vivo. The percentage of IgD-R+ cells peaked after 24 h, was still detectable above background by day 7 or 14, and returned to pre-injection levels by day 28 in young subjects and aged Ab-responders, but not in Ab-nonresponders. Similarly, purified peripheral blood T cells obtained from aged Ab-responders exhibited IgD-R upon immunization in vivo. These findings suggest that Ag injection causes rapid up-regulation of IgD-R by cross-linking IgD in humans as well as in mice as shown previously. In analogy with results in mice, the present data are consistent with a role for IgD-R+ T cells in the humoral response in man. Proliferative responses to influenza proteins in peripheral blood T cells from vaccinated individuals were found to peak on day 7 and were higher in Ab-responders than in Ab-nonresponders.

Adult↗
PubMed1996

Evaluation of presence and functional activity of potentially self-reactive T cells in aged mice.

Autoimmunity is known to increase in aging. A possible factor could be an alteration in the T cell repertoire with advancing age. Antibodies to the variable region of the beta chain of the TCR activate T cells and can serve as probes for analysis of the T cell repertoire. We have used V beta 3 and V beta 17a antibodies to determine the presence and functionality of normally deleted T cells bearing potentially self-reactive TCR in peripheral lymphoid tissue and blood from aged (SJL/J x BALB/c) F1, LAF1 and BALB/c mice. Although an occasional 20- to 24-month-old mouse exhibited V beta 3+ or V beta 17a+ T cells in their lymph nodes or peripheral blood lymphocytes (PBL) slightly above the range for normal young mice of these I-E+ strains, there was no striking 'escape' from the normal thymic deletion process. However, responsiveness to anti-V beta 3 and anti-V beta 17a was slightly higher in aged, and particularly in aged thymectomized (TX), than in young mice. This was in contrast to proliferative responses to stimulation with antibody to the normally expressed V beta 8, which were lower in the lymph nodes from aged than from young mice. The PBL of some 30- to 36-month-old mice were also examined. Enhanced numbers of 'forbidden' V beta bearing T cells were seen more frequently at this age. In spite of the age-related decrease in overall CD4/CD8 T cell ratios in all organs, the mice with relatively high V beta 17a + T cells exhibited proportionally more CD4+ cells in that V beta population. We conclude that the 'forbidden' T cells that respond to anti-V beta stimulation in the 20- to 24-month-old mice are most likely to extra-thymic origin, since they were more readily detectable in aged TX mice. Potentially self-reactive Cd4 (and CD8) single-positive T cells were detectable in PBL only in very aged (30-36 months old) euthymic mice.

Aging↗
PubMed1996

The physiology of germinal centers.

GCs contain Ag-induced rapidly proliferating B cell blasts called centroblasts and centrocytes and are located in primary follicles of peripheral lymphoid tissue. Their peak development is at 7 to 10 d after Ag. The generation of memory B cells occurs in GCs, accompanied by frequent Ig isotype switching, Ig gene V region somatic hypermutation, and/or (in rabbits) gene conversion. The nature and function of the cell types that make up the microenvironment of the GC B cells, the CD4+ T cells and FDCs, are discussed in detail. The high rate of apoptosis that occurs in GCs is thought to be the result of processes of positive and negative selection ongoing in different compartments of GCs. The rescue of cells through high-affinity interaction with Ag localized on FDCs and subsequent presentation of Ag by GC B cells to T cells may represent the positive selection with apoptosis as the default pathway. Negative selection may occur, aimed at the prevention of autoimmunity caused by cells with mutated sIg binding to autoAgs. Some aspects of GC-derived lymphomas in humans and mice are also reviewed.

Animals↗
PubMed1995

Relationship between humoral immunoaugmenting properties of DHEAS and IgD-receptor expression in young and aged mice.

IgD-receptors are associated with augmented antibody production in vivo and are induced on CD4+ T cells by aggregated IgD in young but not in aged mice. In the current study orally or intraperitoneally administered DHEAS was found to enhance antibody production, as measured in a plaque-forming cell assay, and also to cause an increased expression of IgD-R on T cells in both young and aged mice. IgD-R+ T cells are enumerated by rosette cell formation with IgD-coated SRBC. Since, as shown previously, the immunoaugmenting effect of IgD-R+ T cells is blocked by injection of monomeric IgD, the effect of monomeric IgD was also examined in DHEAS-pretreated mice. The inhibitory effect obtained with monomeric IgD in these studies indicates that upregulation of IgD-R by DHEAS plays an important role in the immunoenhancing effect of this hormone. In addition, no significant effect of DHEAS was obtained on contact hypersensitivity to DNCB or on proliferative responses of T cells from young or aged mice. Aged but not young mice showed increases in the numbers of Ia+ epidermal Langerhans cells after DHEAS treatment.

Adjuvants, Immunologic↗
PubMed1995

Oligomeric IgD augments and monomeric IgD inhibits the generation of IgG memory antibody responses in normal, but not in IgD-deficient, mice.

Dimeric or aggregated IgD causes augmentation of primary and secondary Ab responses in mice when injected a few days before or together with the primary dose of Ag. This effect is mediated by Th cells and seems to be linked to the up-regulation of receptors for IgD on CD4+ T cells. IgD-R cross-linking is needed for receptor up-regulation. Here we show that addition of monomeric IgD to dimeric or aggregated IgD blocks IgD-R up-regulation on T cells in vitro and in vivo, as well as their immunoaugmenting effect in vivo. More importantly, monomeric IgD injected 6 to 24 h before a primary Ag injection also inhibits 1) the up-regulation of IgD-R on T cells induced by Ag injection alone, and 2) the generation of IgG memory, as shown in the response to a second dose of Ag injected on day 10. These results suggest that IgD-R on T cells contribute to the T-B cell interaction involved in the priming for a secondary response. The augmenting effect of oligomeric IgD and the inhibiting effect of monomeric IgD on secondary Ab responses are not observed in IgD-/- (IgD-deficient) mice, although injection of oligomeric IgD leads to IgD-R up-regulation on T cells in these mice. These results indicate that IgD presented in the form of immune complexes, most likely on the surface of B cells, is a prerequisite for the immunoaugmenting effects exerted by IgD-R+ T cells. Thus, IgD is the only physiologic ligand for IgD-R on T cells.

Animals↗
PubMed1995

Staphylococcal enterotoxin B and tumor-necrosis factor-alpha-induced relapses of experimental allergic encephalomyelitis: protection by transforming growth factor-beta and interleukin-10.

A study was made of the ability of the superantigen staphylococcal enterotoxin B (SEB) to induce relapses of experimental allergic encephalomyelitis (EAE) in SJL mice that had partially or completely recovered from acute EAE. We find that a single injection of 0.05 mg SEB i.v. induces mild relapses in 50% of such mice. In addition, tumor necrosis factor (TNF)-alpha (0.2 micrograms, i.p.) also induces EAE relapses in 43% of SJL mice when injected 1-2 months after recovery. SEB does not induce a second relapse if reinjected when V beta 17a+T cells are still partially deleted. In these mice, however, TNF-alpha is equally effective in inducing relapses as in mice that did not receive SEB previously. We showed earlier that transforming growth factor (TGF)-beta and TNF-alpha have antagonistic effects on experimental autoimmune diseases; e.g., in spontaneously relapsing EAE, TGF-beta and anti-TNF were protective, while anti-TGF-beta caused disease exacerbation. Interleukin (IL)-10 is also known to counteract certain TNF effects. We now find that both human IL-10 and TGF-beta 2 lower the incidence of EAE relapses when given simultaneously with SEB or TNF-alpha. The protective effect of TGF-beta is significant only against relapses induced by SEB (reduced to 9%), and that of IL-10 only against relapses induced by TNF (reduced to 0%) with the treatment regimens employed. Neutralizing anti-TGF-beta does not increase the incidence of SEB-induced EAE relapses. In contrast, anti-IL-10 increases both the incidence and the severity of such relapses. We conclude that TNF production is probably important in causing EAE relapses, but that other aspects of the SEB-induced reactivation of myelin-specific T cells also contribute. Furthermore, endogenous IL-10 rather than TGF-beta production appears to limit the susceptibility to induction of EAE relapses in this model.

Animals↗
PubMed1995

Synergism between interferon-gamma and cytokines or lipopolysaccharide in the activation of the HIV-LTR in macrophages.

Macrophages (møs) obtained from transgenic mice carrying the HIV long terminal repeat-chloramphenicol acetyl transferase (LTR-CAT) sequence were used to study the influence of various biologic response modifiers (BRMs) on the activation of LTR-directed CAT expression. It was found that LPS or IL-6 alone induced moderate levels of CAT expression, whereas IFN-gamma or TNF-alpha had no significant effect. Co-exposure of møs to IFN-gamma and either LPS, IL-6, or TNF-alpha led to significant synergistic increases in CAT levels. Levels were also synergistically augmented when møs were exposed first to IFN-gamma (priming), washed, and then exposed to either LPS, IL-6, or TNF-alpha. Although IL-6 was synergistic with subsequently added IFN-gamma, the reverse sequence of addition was more effective. LPS and TNF-alpha were inactive when added before IFN-gamma. Initial priming signals were rapid as exposure for 3 h to IFN-gamma was sufficient to prepare the cells for subsequent activation by other BRMs. These results suggest that the duration of latency and progression of HIV infections may be greatly influenced by events such as intercurrent infections that cause IFN-gamma production, thereby priming møs to respond to other cytokines that have been reported to be constitutively elevated during the course of infection with HIV (e.g., IL-6 and/or TNF-alpha).

Animals↗
PubMed1995

Tolerogenic forms of auto-antigens and cytokines in the induction of resistance to experimental allergic encephalomyelitis.

Resistance to experimental allergic encephalomyelitis (EAE) induction by homogenized myelin (MSCH) in complete Freund's adjuvant (CFA) and pertussigen (P) in SJL mice was seen 1 week after intravenous injection of PLP 139-151 coupled to spleen cells (PLP-ECDI-SP). Although this resistance could be transferred by spleen cells enriched for CD8+ T cells and thus had a component of immunoregulatory T cells, it was primarily due to anergy, as it was reversible by four daily injections of interleukin (II)-2 starting 3 days after the PLP-ECDI-SP. Earlier treatment with IL-2 did not reverse the tolerance. In view of the known higher sensitivity to anergy induction of Th1 than of Th2 cells, a change in the cytokine balance in the response to MSCH+CFA after anergy induction might be responsible for the resistance to EAE induction. The effect of treatment with cytokines alone on induction of EAE was therefore also determined. Short-term (1-2 weeks) daily pretreatment with IL-2 (4000 U) or TGF-beta 2 (1 micrograms) somewhat decreased the susceptibility to subsequent EAE induction, but IL-4 (5 ng), IL-10 (5 micrograms) or IL-12 (50-200 ng) had no effect under those conditions, even if low doses of PLP were injected simultaneously. Daily injections of IL-4 over an 8-week period prior to immunization, however, significantly lowered the incidence of EAE. Simultaneous injections of IFN-gamma (2000 U/day) completely abolished this effect of IL-4. The effect of these cytokines administered immediately after the immunization with MSCH + CFA + P was also examined. As shown earlier, TGF-beta 2 (100-1000 ng/day) caused a marked protection when it was given intraperitoneally on days 5-9 after injection of MSCH + CFA. IL-4 (5 ng/day), in contrast, was very protective when administered on days 0-4 and less so when given on days 5-9 or even on days 0-12. IL-10 (1 microgram/day) was not protective under these conditions and IL-12 (50 ng/day) significantly increased the severity and mortality of EAE when given on days 0-4 after MSCH + CFA.

Animals↗
PubMed1995

The Emu-bcl-2 transgene enhances antigen-induced germinal center formation in both BALB/c and SJL mice but causes age-dependent germinal center hyperplasia only in the lymphoma-prone SJL strain.

Emu-bcl-2 transgenic and littermate control BALB/c and SJL mice were immunized in the front footpads with trinitrophenylated Brucella abortus and the germinal center (GC) response in draining brachial lymph nodes was studied by staining with peanut agglutinin peroxidase and methyl green. Although the GCs induced were not larger in transgenic than in control young mice, there was a significant increase in the percentage of B cell follicles exhibiting GCs 7 to 8 days after primary and secondary antigen injections in the transgenic mice of both strains. In addition, glucocorticosteroid injected on day 7 after the primary injection caused a marked decrease in GCs in littermate controls but had no effect in the bcl-2 transgenic SJL mice. Antibody production to B. abortus was only slightly higher in transgenic than in control mice, but anti-TNP immunoglobulin M and G titers were significantly enhanced in the transgenic mice. The bcl-2 transgenic SJL mice, older than 6 months, showed the spontaneous appearance of large numbers of peanut agglutinin-binding GCs that greatly varied in size and were located without regard for the normal lymph node structure or follicle localization. This GC hyperplasia was seen in a large percent of the older transgenic SJL mice and never in similarly aged normal SJL or BALB/c mice with and without the bcl-2 transgene. Frank lymphomatous transformation of peanut agglutinin-binding germinal center-like areas was seen in lymph nodes and Peyer's patches of some of the older bcl-2 transgenic SJL mice. These results suggest that the tendency of SJL mice to develop GC-derived lymphomas synergizes with the presence of the bcl-2 transgene to cause the development of GC hyperplasia.

Aging↗
PubMed1994

Biology of germinal centers in lymphoid tissue.

Germinal centers in lymphoid tissue are the sites of generation of memory B cells undergoing isotype switching and somatic mutation in their Ig genes. Their formation cannot be induced by stimuli other than immunogenic ones. It seems likely that in the function and possibly also in the formation of germinal centers, one important factor is the localization of immune complexes with fixed complement on the surface of follicular dendritic cells. CD4+ T cells, located primarily in the "apical light zones" of the centers, are necessary for germinal center formation. However, their exact role in the process needs clarification, as both cell to cell contact and cytokine production could be involved at different stages of the germinal center generation. These T cells are usually specific for the antigen inducing the germinal center, but they may sometimes respond to other surface components on the B cell surface. In view of the possible stimulatory role of CD4+ T cells in follicular center-derived lymphomas, the functional significance of these T cells in germinal center proliferation is important to unravel. The B cells in germinal centers proliferate extremely rapidly, especially those located in the "dark zones." Many of them undergo apoptosis, particularly in the "basal light zones." The microenvironment of these centers is well suited to the task of expanding and selecting memory B cells of high affinity for the inducing antigen. The interactions of the proliferating B cells with dendritic cells and T cells, unevenly distributed in the various zones of the germinal center, are thought to determine which cells deserve rescue from apoptosis and induction to differentiation into small resting memory B cells. The memory B cells that emerge from the germinal center bear sIg, usually of "switched" isotype, and exhibit somatic mutations in the variable regions of their rearranged Ig genes.

Aging↗