SITES OF FORMATION OF IMMUNE GLOBULINS AND OF A COMPONENT OF C'(3): II. PRODUCTION OF IMMUNOELECTROPHORETICALLY IDENTIFIED SERUM PROTEINS BY HUMAN AND MONKEY TISSUES IN VITRO

Human, and monkey tissues were cultured in the presence of labeled amino acid. The culture fluids were then examined for labeled serum proteins by means of autoradiography of immunoelectrophoretic patterns prepared from mixtures of the fluids and carrier sera. Gamma globulin, β_2A-globulin, β_2Mglobulin, and β_1C-globulin were found to be formed in human lymph node, bone marrow, and ileum. Gamma globulin, β_2M-globulin, and β_1C-globulin were found to be formed in monkey spleen, lymph node, and bone marrow. Formation of several other serum proteins was observed in the monkey liver.

SITES OF FORMATION OF IMMUNE GLOBULINS AND OF A COMPONENT OF C'(3): I. A NEW TECHNIQUE FOR THE DEMONSTRATION OF THE SYNTHESIS OF INDIVIDUAL SERUM PROTEINS BY TISSUES IN VITRO

The development of a new method for the determination of the sites of serum protein formation has been described. The method involves the incorporation of C(14)-labeled amino acids by tissues cultured in vitro, and subsequent autoradiography of immunoelectrophoretic patterns prepared from a mixture of culture fluids and carrier serum with an antiserum against the carrier serum. This technique has been used to demonstrate formation of gamma-globulin, of beta(2)-macroglobulin, and of a component of C'(3) by mouse spleen tissue, and of various other serum proteins by liver tissue. The specificity and sensitivity of this method have been discussed, and some of its advantages and pitfalls were mentioned. In addition, a rabbit antimouse serum was prepared, and the immunoelectrophoretic patterns obtained with mouse serum were compared with those described in the literature.

Appearance of Langerhans cells in the epidermis of Tgfb1(-/-) SCID mice: paracrine and autocrine effects of transforming growth factor-beta 1 and -beta 2(1)

A striking immunologic abnormality of normal and SCID Tgfb1(-/-) mice is the total absence of Langerhans cells in their epidermis. Here we show that transfer of Tgfb1(+/-) SCID bone marrow causes, within a few weeks, the appearance of Langerhans cells in the epidermis of gamma-irradiated and unirradiated Tgfb1(-/-) SCID recipients. In addition, local injection of 2 x 10(5) latent transforming growth factor-beta1 cDNA-transduced cloned CD4+ T lymphocytes causes the appearance of Langerhans cells in the ear epidermis of Tgfb1(-/-) SCID mice. This effect is enhanced by antigen-specific activation of these T cells. Injection of recombinant active transforming growth factor-beta 2 into the ear of Tgfb1(-/-) SCID mice also results in the migration of Langerhans cells into the epidermis locally, but no epidermal Langerhans cells are seen after systemic injections of transforming growth factor-beta 2. Our results suggest that transforming growth factor-beta can act in paracrine as well as autocrine fashion to induce the differentiation of precursors into Langerhans cells. Furthermore, these results indicate that the relative roles of different transforming growth factor-beta isoforms in vivo may be influenced by their local availability and/or the regulation of their conversion from latent into active form.

META-controlled env-initiated transcripts encoding superantigens of murine Mtv29 and Mtv7 and their possible role in B cell lymphomagenesis

Spontaneous germinal center (GC)-derived B cell lymphomas of SJL mice (RCS) transcribe a 1.8-kb Mtv-29 mRNA under control of the META-env promoter. The encoded vSAg29 stimulates syngeneic Vbeta16(+) CD4(+) T cells, thereby acquiring T cell help necessary for RCS growth. Other strains of B cell lymphoma-prone mice include Mtv29(+) C57L and MA/MyJ, and the Mtv29(-) Mtv7(+)-recombinant inbred strain, SW x J-1. The lymphomas of these mice produce similar mouse mtv-vSAg-encoding mRNA, as characterized by Northern blotting, PCR, and RNase protection. A 1.8-kb mRNA in C57L/J and MA/MyJ lymphomas hybridized with an Mtv29-specific oligonucleotide, whereas SW x J-1 lymphomas produced 1.8-kb transcripts hybridizing with an Mtv7-specific oligonucleotide. Similar META-env-initiated transcripts were absent from LPS-activated B cells from any strain examined but were detected in Peyer's patch RNA from SJL mice. Like typical SJL-derived RCS, all these lymphomas stimulated syngeneic CD4(+) T cells and Vbeta16(+) T hybridoma cells. Immunohistochemical staining of primary tumors showed the presence of peanut agglutinin binding (PNA(+)) highly mitotic lymphoblasts, suggesting their GC derivation. The findings indicate that this novel mRNA for Mtv29 is present in B cell lymphomas from several Mtv29(+) mouse strains. Additionally, this is the first description of the ability of Mtv7 to produce transcripts that are controlled and spliced identically to those of Mtv29 and that are expressed in SW x J-1, I-A(s+), lymphomas that also stimulate Vbeta16(+) T cells. Our results suggest an important role for mouse mtv-vSAgs and Vbeta16 T cell stimulation in the development of GC-derived murine B cell lymphomas.

Induction of germinal centers by MMTV encoded superantigen on B cells

It has not been established whether an endogenous superantigen (SAg) expressed on B cells can induce germinal centers (GCs). An interesting model is that of mammary tumor virus encoded viral SAgs, which induce vigorous T cell proliferation and are predominantly expressed on activated B cells. We have used this model to analyze the possibility that direct stimulation of Mtv7+ DBA/2 B cells by vSAg-responsive (Vbeta6+) BALB/c T cells can give rise to GCs. Injection of BALB/c SCID mice i.v. with 2 x 10(6) DBA/2 B cells, together with LPS, followed by 2 x 10(6) BALB/c T cells induces numerous large splenic GCs within 3-5 days. The GCs are still large on day 7, but are very much reduced by day 10. B cell activation with LPS is needed for this effect. These GCs form in spite of the apparent absence of follicular dendritic cells (FDCs) as judged by staining for several FDC surface markers. Control mice receiving either BALB/c T or DBA/2 B cells + LPS alone or DBA/2 T + B cells + LPS fail to exhibit any GCs on days 3-7. Numerous small clusters of PNA+ cells, but few large GCs are observed when TNF-R(p55)-Ig is also injected, whereas LTbetaR-Ig treatment impeded the formation of aggregations of these cells even further, leaving scattered PNA+ single cells and very small clumps throughout the white pulp of the spleens. Anti-TNFalpha had no effect. These results suggest that endogenous vSAg mediated GC formation is independent of antigen trapping by FDCs.

Amelioration of collagen-induced arthritis in DBA/1J mice by recombinant TSG-6, a tumor necrosis factor/interleukin-1-inducible protein

OBJECTIVE

To examine the effect of recombinant TSG-6 on collagen-induced arthritis (CIA) in DBA/1J mice. TSG-6 is a tumor necrosis factor (TNF)/ interleukin-1 (IL-1)-inducible hyaluronan-binding protein produced by synovial cells and chondrocytes that is present in synovial fluids of patients with rheumatoid arthritis.

METHODS

To determine the effect of TSG-6 on chronic inflammatory joint disease, we induced CIA in DBA/1J mice by immunization with bovine type II collagen. Animals were treated with 12 intraperitoneal doses of 200 microg of recombinant TSG-6, beginning 3 days before the expected onset of disease symptoms. Progression of arthritis was monitored by determining the disease incidence, arthritis index, and footpad swelling. Levels of IgG1, IgG2a, and IgG2b antibodies against bovine and murine type II collagen and serum concentrations of IL-6 were determined at various time points. Histologic examination of affected joints was performed approximately 20 days after the onset of arthritis.

RESULTS

Treatment with recombinant TSG-6 protein had a potent ameliorative effect, manifested by decreases in the disease incidence, arthritis index, and footpad swelling. Histologic examination of affected joints in TSG-6-treated animals revealed little pannus formation and cartilage erosion, features which were conspicuous in control mice. Animals treated with recombinant TSG-6 developed significantly reduced levels of IgG1, IgG2a, and IgG2b antibodies against bovine and murine type II collagen.

CONCLUSION

The antiinflammatory effect of the TNF/IL-1-inducible TSG-6 protein in murine CIA suggests a role for this protein as an endogenous regulator of the inflammatory process.

Requirement for reverse immune surveillance for the growth of germinal center-derived murine lymphomas

The concept of reverse immune surveillance, first conceived over 12 years ago, described the relationship that existed between germinal center-derived B cell lymphoma cells and the host immune system in SjL/J mice. According to reverse immune surveillance, recognition of tumor cell antigens and a response by the host immune system is required for tumor growth. The phenomenon of reverse immune surveillance related to B cell lymphomas has recently also been characterized in another inbred mouse strain, C57L/J. Moreover, elements of reverse immune surveillance have been observed in several other mouse strains that develop B cell lymphomas, suggesting that this lymphomagenic mechanism may be more common than first envisioned. In SJL and C57L mice, the B lymphoma cells express an MMTV-encoded superantigen (vSAg29) that stimulates syngeneic CD4+ T cells bearing Vbeta16 in their TCR. In contrast to the mRNAs for other MMTVs in normal mouse B cells, vSAg29 mRNA initiates in the env (META) region, undergoes splicing in the 3' env region, and continues through the 3' LTR. Copious cytokine production, including IFN-gamma, IL-4 and IL-5 accompanies the response of the T cells to this vSAg. In addition to cytokines produced by vSAg-responsive T cells, more recent evidence indicates that another cytokine, LTalphabeta2, which is expressed on the lymphoma cell surface, also plays a role in the promotion of the B cell lymphoma growth. It is possible that interaction with LTbeta-R on follicular dendritic cells or other stromal elements facilitates tumor growth by preventing apoptosis of the malignant B cells. To what degree these findings in the mouse are relevant to the development and/or growth of human B lymphoma cells remains to be determined. However, endogenous retroviral sequences do exist in the human genome. Interestingly, some of these sequences are homologous to MMTV, and are transcribed in B lymphoblastoid cells. Moreover microorganisms that are infectious for human B cells, such as EBV and Herpes Virus 8, may also produce superantigens.

When engineered to produce latent TGF-beta1, antigen specific T cells down regulate Th1 cell-mediated autoimmune and Th2 cell-mediated allergic inflammatory processes

To determine whether T cells which produce large amounts of latent TGF-beta1 are capable of down-regulating autoimmune and allergic disease, myelin basic protein (MBP)-specific and ovalbumin (OVA)-specific BALB/c cloned Th1 cells were transduced with cDNA for murine TGF-beta1 by coculture with fibroblasts producing a genetically engineered retrovirus. The transduced MBP-specific Th1 cells were found to lose the capacity to provoke EAE in BALB/c mice, and to gain instead the ability to protect against EAE in (SJLxBALB/c) F1 mice immunized with proteolipid protein (PLP). This protective effect was not obtained with OVA-specific TGF-beta1 transduced Th1 cells. The transduced OVA-specific Th1 cells did protect against airway hyperreactivity induced by Th2-cell mediated responses to inhaled OVA. This effect was again antigen specific and it also could not be obtained with untransduced OVA-specific Th1 cells. In both cases these effects of antigen specific TGF-beta1 transduced T cells were nullified by administration of neutralizing anti-TGF-beta mAb. Thus, the antigen specificity of the cloned T cells allows the site-specific local delivery of therapeutic active TGF-beta1 to both Th1 and Th2 cell-mediated inflammatory infiltrates.

CD4(+) T helper cells engineered to produce latent TGF-beta1 reverse allergen-induced airway hyperreactivity and inflammation

T helper 2 (Th2) cells play a critical role in the pathogenesis of asthma, but the precise immunological mechanisms that inhibit Th2 cell function in vivo are not well understood. Using gene therapy, we demonstrated that ovalbumin-specific (OVA-specific) Th cells engineered to express latent TGF-beta abolished airway hyperreactivity and airway inflammation induced by OVA-specific Th2 effector cells in SCID and BALB/c mice. These effects correlated with increased concentrations of active TGF-beta in the bronchoalveolar lavage (BAL) fluid, demonstrating that latent TGF-beta was activated in the inflammatory environment. In contrast, OVA-specific Th1 cells failed to inhibit airway hyperreactivity and inflammation in this system. The inhibitory effect of TGF-beta-secreting Th cells was antigen-specific and was reversed by neutralization of TGF-beta. Our results demonstrate that T cells secreting TGF-beta in the respiratory mucosa can indeed regulate Th2-induced airway hyperreactivity and inflammation and suggest that TGF-beta-producing T cells play an important regulatory role in asthma.

CD30 overexpression enhances negative selection in the thymus and mediates programmed cell death via a Bcl-2-sensitive pathway

The biological function of CD30 in the thymus has been only partially elucidated, although recent data indicate that it may be involved in negative selection. Because CD30 is expressed only by a small subpopulation of medullary thymocytes, we generated transgenic (Tg) mice overexpressing CD30 in T lymphocytes to further address its role in T cell development. CD30 Tg mice have normal thymic size with a normal number and subset distribution of thymocytes. In vitro, in the absence of CD30 ligation, thymocytes of CD30 Tg mice have normal survival and responses to apoptotic stimuli such as radiation, dexamethasone, and Fas. However, in contrast to controls, CD30 Tg thymocytes are induced to undergo programmed cell death (PCD) upon cross-linking of CD30, and the simultaneous engagement of TCR and CD30 results in a synergistic increase in thymic PCD. CD30-mediated PCD requires caspase 1 and caspase 3, is not associated with the activation of NF-kappaB or c-Jun, but is totally prevented by Bcl-2. Furthermore, CD30 overexpression enhances the deletion of CD4+/CD8+ thymocytes induced by staphylococcal enterotoxin B superantigen and specific peptide. These findings suggest that CD30 may act as a costimulatory molecule in thymic negative selection.

CD30 in normal and neoplastic cells

In 1982 Stein and coworkers identified a new molecule, CD30 (Ki-1), which is expressed by Reed-Sternberg (RS) cells of Hodgkin's Disease (HD) (1). Although CD30 is not a specific RS cell marker, its characterization has assumed an important role not only in the differential diagnosis of HD, but also in the identification of a morphologically and clinically distinct type of large cell lymphoma, now designated as anaplastic large cell lymphoma (ALCL) (2). The cloning of human and murine CD30 and the utilization of genetically manipulated animal models have rapidly expanded our knowledge on its physiological role in lymphoid development and differentiation. The goal of this review is to present an overview of this rapidly evolving field and discuss the role of CD30 in normal and neoplastic lymphoid cells.

Modulation by cytokines of induction of oral tolerance to type II collagen

OBJECTIVE

To determine whether the simultaneous administration of drugs and/or cytokines such as transforming growth factor beta (TGFbeta) can render oral tolerance to type II collagen (CII) more effective in causing resistance to collagen-induced arthritis (CIA) in mice, and to investigate whether oral tolerance can still be induced when high levels of anti-CII are present.

METHODS

Tolerance was induced by intragastric feeding of low-dose CII to DBA/1 mice during a 2-week period, either before immunization with CII in Freund's complete adjuvant or after initiation of arthritis. Some mice were simultaneously injected with TGFbeta1 or with the H2 receptor agonist dimaprit.

RESULTS

Both TGFbeta1 and dimaprit increased the degree of oral tolerance obtained. TGFbeta1 augmented the induction of immunoregulatory CD8 T cells, which transferred the resistance to CIA induction to normal recipients. Feeding of CII for 2 weeks, starting after the onset of arthritis, still significantly ameliorated the course of CIA.

CONCLUSION

Administration of TGFbeta1 or dimaprit, both of which are believed to promote the development of immunoregulatory T cells, may reinforce induction of oral tolerance, even after the onset of arthritis.

Gene therapy in allergic encephalomyelitis using myelin basic protein-specific T cells engineered to express latent transforming growth factor-beta1

A myelin basic protein (MBP)-specific BALB/c T helper 1 (Th1) clone was transduced with cDNA for murine latent transforming growth factor-beta1 (TGF-beta1) by coculture with fibroblasts producing a genetically engineered retrovirus. When SJL x BALB/c F1 mice, immunized 12-15 days earlier with proteolipid protein in complete Freund's adjuvant, were injected with 3 x 10(6) cells from MBP-activated untransduced cloned Th1 cells, the severity of experimental allergic encephalomyelitis (EAE) was slightly increased. In contrast, MBP-activated (but not resting) latent TGF-beta1-transduced T cells significantly delayed and ameliorated EAE development. This protective effect was negated by simultaneously injected anti-TGF-beta1. The transduced cells secreted 2-4 ng/ml of latent TGF-beta1 into their culture medium, whereas control cells secreted barely detectable amounts. mRNA profiles for tumor necrosis factor, lymphotoxin, and interferon-gamma were similar before and after transduction; interleukin-4 and -10 were absent. TGF-beta1-transduced and antigen-activated BALB/c Th1 clones, specific for hemocyanin or ovalbumin, did not ameliorate EAE. Spinal cords from mice, taken 12 days after receiving TGF-beta1-transduced, antigen-activated cells, contained detectable amounts of TGF-beta1 cDNA. We conclude that latent TGF-beta1-transduced, self-reactive T cell clones may be useful in the therapy of autoimmune diseases.

Human T cell IgD receptors react with O-glycans on both human IgD and IgA1

Previous studies on murine T cell IgD-R have shown that these receptors recognize N-glycans of murine IgD, and not of other Ig isotypes. We have now studied the specificity of IgD-R on human T cells. Human IgD digested with proteinase K to fragments of < 5 kDa inhibit the ability of T cells to form rosettes with IgD-coated ox erythrocytes. The same amount of digested IgG does not. We tested all the human Ig isotypes: IgG1, -2, -3, -4, IgA2, IgE and IgM fail to inhibit significantly at 20 microg/assay. However, IgA1 is as effective as IgD itself, showing approximately 60 % and 80 % inhibition at 5 microg and 10 microg/assay. Human IgA1 and IgD both contain Gal-1 --> 3-GalNac-rich O-linked glycans, and on this basis are both bound to ricin and jacalin. The O-linked glycans may therefore also represent the common moiety binding to IgD-R. Disaccharides Gal-1 --> 3-GalNac, and Gal-1 --> 4-Glc at 10 microg/assay blocked IgD rosetting while Gal-1 --> 6-Glc did not. We conclude that the human IgD-R is a lectin, differing from the murine IgD-R in that it has both IgA1 and IgD as ligands.

Age-related loss of immunoregulatory function in peripheral blood CD8 T cells

CD8+ T cells from young individuals become inhibitory for the (Staphylococcus aureus + interleukin 2)-induced differentiation of autologous B cells into immunoglobulin secreting cells (ISC) after exposure to pokeweed mitogen (PWM), dimaprit or intracellular cAMP raising agents, such as forskolin or dibutyryl-cAMP. In the present study this immunoregulatory activity was found to be lacking in CD8+ T cells from peripheral blood lymphocytes (PBL) of aged (> 67 years old) subjects. Splenic CD8+ T cells from most individuals examined, including some aged subjects, exhibited this activity. While an age-related decrease in the CD8+ T cell subset, primarily in the virgin CD8+ T cells in PBL, was detected, this decrease was not sufficient to explain a total absence of activity. There was no age-related decrease in cAMP upregulation by forskolin or dimaprit in peripheral blood T cells. However, whereas PWM induced a highly significant increase in mRNA for transforming growth factor-beta (TGF-beta) in T cells from young individuals, no such increase could be detected in T cells from aged subjects. It is suggested that the decrease in immunoregulatory activity in PBL from the elderly may at least in part be due to a decrease in TGF-beta production.

The effect of aging on IgD receptor expression by T cells and its functional implications

Exposure to oligomeric or aggregated (a), but not to monomeric (m), IgD causes a rapid (within 1 h) upregulation of IgD-R expression on CD4+ T cells from young, but not from aged, mice and on both CD4+ and CD8+ T cells from all young and from approximately 65% of aged humans. In normal young (but not in IgD-/-) mice, this increase in IgD-R expression is associated with a marked increase in primary and secondary antibody responses, transferable to both aged and young mice with T cells from aIgD pretreated donors. In both species, immunization causes a rise in the IgD-R+ expression in vivo in the young. In mice, mIgD abolishes both the induction of IgD-R expression and augmentation of immune responses, suggesting that interaction between IgD-R+ T and IgD+ B cells is needed. In aged humans, the ability of peripheral blood lymphocytes to exhibit IgD-R expression in response to aIgD in vitro or to influenza vaccine in vivo is strongly correlated to the individual's ability to produce antibody. In T cells from aged mice, but not from aged IgD-non-responder humans, IgD-R are able to come to the cell surface if an additional signal has been supplied, such as by (ionomycin/thapsigargin + aIgD). Agents which induce IgD-R and augmentation of antibody production in aged and young mice include phosphatidylcholine and dehydroepiandrosterone sulfate. The immunoaugmenting effect of pretreatment with these agents appears indeed due to IgD-R+ T cells, because it is abolished by mIgD.

The effect of aging on the immune response: influence of phosphatidylcholine-containing lipid on IgD-receptor expression and antibody formation

It was reported previously that IgD-receptors (IgD-R) are expressed on both CD4+ and CD8+ human T cells and CD4+ murine T cells after exposure to oligomeric IgD, certain cytokines, or various pharmacological agents, as shown by rosetting with IgD-coated erythrocytes. Enhancement of antibody production is observed in mice after injection of oligomeric IgD and is mediated by these IgD-R+ T cells, while injection of monomeric IgD inhibits both IgD-R upregulation and augmentation of antibody responses induced by simultaneously injected oligomeric IgD. The effects of oligomeric IgD on IgD-R upregulation are lacking in aged mice. However, the oligomeric IgD induced enhanced antibody production can be transferred to aged mice with IgD-R+ T cells from young donors suggesting that the environment of the aged mouse supports the effector function of IgD-R+ T cells. We now report, in addition, that exposure to phosphatidylcholine (PC) and a PC-containing lipid mixture, AL721, is effective in causing IgD-R upregulation on T cells from both young and aged mice, and young humans. This effect can also be demonstrated in mice in vivo after administration of AL721. Moreover, this agent causes a two-fold enhancement of antibody production, as measured by PFC/spleen, to 4-hydroxy-5-iodo-3-nitrophenyl(acetyl)-Brucella abortus (NIP-BA) and NIP-horse red blood cells (RBC) in young and aged mice. There is no difference in the baseline membrane fluidity of lymphocytes from aged and young mice. Although PC causes an increase in membrane fluidity of lymphocytes from both young and old mice, and from humans, this effect on fluidity is not prevented by a protein kinase inhibitor, while PC's effect on IgD-R upregulation is prevented by the inhibitor. Moreover, no correlation was observed between IgD-R upregulation and membrane fluidity changes induced by AL721 administered in vivo. To evaluate the role of IgD-R induction in the augmentation of antibody production by phospholipids, the effect of monomeric IgD was investigated. The augmenting effect of AL721 on antibody production was prevented by a single injection of monomeric IgD at the time of antigen administration. We conclude that (1) PC-containing lipid mixtures are effective in enhancing antibody production in aged mice, (2) induction of IgD-R is responsible for the augmenting effects of AL721 on antibody production, and (3) monomeric IgD not only blocks the upregulation of IgD-R, as shown previously, but also the augmenting effect of previously upregulated IgD-R on T cells by preventing their interaction with surface IgD+ B cells.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

Regulation of IgD-receptor expression on murine T cells. II. Upregulation of IgD receptors is obtained after activation of various intracellular second-messenger systems; tyrosine kinase activity is required for the effect of IgD

The presence of IgD receptors (IgD-R) on T cells during a primary response to antigen causes augmented antibody production and facilitates priming for a secondary response. Cross-linked, but not monomeric IgD leads to a rapid upregulation of these receptors on T cells. As shown in the present study, the rapid upregulation of IgD-specific receptors is also induced by cross-linking of T cell surface molecules known to mediate triggering of T cell activation, such as CD3, CD2, and Thy 1. Furthermore, IgD-R are also upregulated by pharmacologically active compounds that increase intracellular cAMP and by PMA/DiOG plus ionomycin, but not by either PMA or ionomycin alone. The upregulation of IgD-R by anti-CD3 is inhibited by both calphostin C and herbimycin A, while that due to DiOG plus ionomycin is only inhibited by calphostin C. Upregulation of IgD-R by increased cAMP is blocked by HA1004, but not by low concentrations of staurosporine or herbimycin A. IgD itself does not cause an increase in intracellular cAMP, protein kinase C translocation, influx of extracellular Ca2+, or a change in membrane potential. Relatively specific inhibitors of these activation pathways, HA1004, calphostin C, and neomycin, also fail to interfere with IgD-receptor upregulation by IgD itself. However, tyrosine kinase inhibitors, including herbimycin A, tyrphostin C11, and genistein, completely prevent the effect of IgD on IgD-R expression. Although an influx of Ca2+ is apparently not involved, a role for intracellular Ca2+ in the upregulation of IgD-R by IgD on T cells is indicated by the susceptibility to inhibition by BAPTA, W7, and FK520. We conclude that activation of at least three different second-messenger systems can cause IgD-R upregulation, but that the effect of IgD itself requires tyrosine kinase activity, perhaps in an intracellular Ca(2+)-dependent manner.

Regulation of IgD-receptor expression on murine T cells. I. Characterization and metabolic requirements of the process leading to their expression

Receptors for IgD (IgD-R) are found on murine CD4+ T cells and T cell clones. Previous work has shown that incubation with aggregated (but not monomeric) IgD causes the rapid upregulation of IgD-R and enables the T cells to respond with augmented helper function in antibody production. In the present study, IgD-R upregulation is shown to be (a) rapid, reaching plateau levels by 60 min, (b) independent of de novo protein or RNA synthesis, and (c) only slightly reduced at 4 degrees C. The IgD-R+ T cells present both before and after upregulation of IgD-R expression are predominantly resting T cells, whose ability to rosette with IgD-SRBC is inhibited by soluble IgD. The upregulation of IgD-R, even after overnight exposure to IgD, does not cause any detectable change in the expression of other T cell surface markers. Also characteristic of resting T cells is that they exhibit IgD-R in response to IL-2 and IL-4 only after overnight incubation with these cytokines, and fail to respond at all to IL-1. In contrast, cloned Th2 cells, expressing IL-1 and IL-2 receptors, show IgD-R upregulation after a 2-hr exposure to IL-1 or IL-2. GM-CSF, TNF-alpha, IL-6, and IL-10 do not modulate IgD-R expression. T hybridoma cells constitutively express much higher IgD-R levels than resting splenic T cells and can be stained with aggregated IgD followed by FITC-anti-IgD. Their levels of IgD-R expression decrease, as assayed both by rosetting and by staining, on 4-14 hr of incubation with tunicamycin or deoxynojirimycin, suggesting that N-linked glycosylation and oligosaccharide processing, respectively, are needed for continued expression of IgD-R. Tunicamycin-treated cells without detectable IgD-R on their surface still show IgD-binding protein in the cell extracts, suggesting that surface expression is more dependent on glycosylation of the IgD-R molecules than on the ability to bind IgD. Ca2+ ions are needed for optimal binding of IgD to IgD-R, in line with previous findings showing IgD-R to be lectin-like in binding carbohydrate rather than peptide regions of the IgD molecule.

Antagonistic effects of endogenous and exogenous TGF-beta and TNF on auto-immune diseases in mice

Injection of transforming growth factor beta 1 (TGF-beta 1) for five days during the late phase of the immunization process leading either to collagen type II induced arthritis (CIA) or to experimental allergic encephalomyelitis (EAE) protects against the development of these auto-immune diseases. Tumor necrosis factor alpha (TNF-alpha) injected during this same interval aggrevates CIA. In addition, anti-TGF-beta exacerbates and anti-TNF protects against CIA, acute and relapsing EAE, suggesting an important regulatory role for the endogenous production of the two cytokines on the severity of these diseases. More detailed studies about the mechanism of action of TGF-beta in acute EAE show that there is no detectable effect of TGF-beta on the development of sensitized T cells in vivo, as assayed by the proliferative responses of T cells from lymph nodes and peripheral blood to myelin antigens. Nevertheless, the number of lymphoid cells infiltrating the central nervous tissue is much greater in untreated than in TGF-beta-treated, protected mice. We conclude that it is likely that TGF-beta protects against experimental auto-immune diseases by interfering with the entry of lymphoid cells into the target organs through inhibition of the upregulation of adhesion molecule expression on endothelial cells, and with subsequent inflammatory processes inside the target organs by antagonizing both the production and the effects of TNF.

Studies on the mechanisms by which transforming growth factor-beta (TGF-beta) protects against allergic encephalomyelitis. Antagonism between TGF-beta and tumor necrosis factor

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease in which peripheral lymphoid cells are activated by immunization with myelin proteins and become effector cells that traverse the central nervous system (CNS) capillaries and initiate inflammatory demyelinating lesions. The administration of transforming growth factor-beta (TGF-beta) has been shown previously to decrease the incidence and severity of EAE. In our studies we have determined: 1) the effects of TGF-beta injected at different intervals after the EAE-inducing immunization; 2) the effect of TGF-beta on the development of sensitized T cells, as assayed by the proliferative responses of T cells from lymph nodes and peripheral blood; 3) the extent of lymphoid cell infiltration in CNS of TGF-beta-treated and control mice; and 4) the role of endogenous TGF-beta and TNF in determining the severity of both acute and relapsing EAE. The onset of acute-EAE in SJL mice, induced by immunization with spinal cord homogenate in CFA and pertussigen, is on days 10 to 15. Although daily i.p. injections of 0.2 to 2 micrograms TGF-beta 1 or TGF-beta 2 on days 5 to 9 after immunization are highly protective, injections on days 1 to 5 or 9 to 13 are not. Moreover, anti-TGF-beta accelerates and aggrevates EAE when given on days 5 and 9, but not on day 12. Anti-TNF, injected on days 5 and 9, provides a comparable degree of protection as does TGF-beta. Similarly, in relapsing EAE, anti-TGF-beta increases, whereas anti-TNF decreases the incidence and severity of relapses. TGF-beta treatment on days 5 to 9 does not influence the appearance of sensitized cells in peripheral blood and lymph nodes, but does prevent the accumulation of T cells in brain and spinal cord, as assayed on days 15 to 20. It is concluded that the protective effect of TGF-beta is exerted at the level of the target organ, CNS and/or its vascular endothelium, rather than through a direct effect on lymphoid cells, and that there is a small window of 4 days in which TGF-beta exerts its protective effect.

Studies on the mechanisms by which transforming growth factor-beta (TGF-beta) protects against allergic encephalomyelitis. Antagonism between TGF-beta and tumor necrosis factor

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease in which peripheral lymphoid cells are activated by immunization with myelin proteins and become effector cells that traverse the central nervous system (CNS) capillaries and initiate inflammatory demyelinating lesions. The administration of transforming growth factor-beta (TGF-beta) has been shown previously to decrease the incidence and severity of EAE. In our studies we have determined: 1) the effects of TGF-beta injected at different intervals after the EAE-inducing immunization; 2) the effect of TGF-beta on the development of sensitized T cells, as assayed by the proliferative responses of T cells from lymph nodes and peripheral blood; 3) the extent of lymphoid cell infiltration in CNS of TGF-beta-treated and control mice; and 4) the role of endogenous TGF-beta and TNF in determining the severity of both acute and relapsing EAE. The onset of acute-EAE in SJL mice, induced by immunization with spinal cord homogenate in CFA and pertussigen, is on days 10 to 15. Although daily i.p. injections of 0.2 to 2 micrograms TGF-beta 1 or TGF-beta 2 on days 5 to 9 after immunization are highly protective, injections on days 1 to 5 or 9 to 13 are not. Moreover, anti-TGF-beta accelerates and aggrevates EAE when given on days 5 and 9, but not on day 12. Anti-TNF, injected on days 5 and 9, provides a comparable degree of protection as does TGF-beta. Similarly, in relapsing EAE, anti-TGF-beta increases, whereas anti-TNF decreases the incidence and severity of relapses. TGF-beta treatment on days 5 to 9 does not influence the appearance of sensitized cells in peripheral blood and lymph nodes, but does prevent the accumulation of T cells in brain and spinal cord, as assayed on days 15 to 20. It is concluded that the protective effect of TGF-beta is exerted at the level of the target organ, CNS and/or its vascular endothelium, rather than through a direct effect on lymphoid cells, and that there is a small window of 4 days in which TGF-beta exerts its protective effect.

Syngeneic response to SJL follicular center B cell lymphoma (reticular cell sarcoma) cells is primarily in V beta 16+ CD4+ T cells

The growth of SJL B cell lymphomas (RCS, reticulum cell sarcoma) in vivo and in vitro is known to depend on cytokine production by RCS-responsive host CD4+ T cells. The high frequency of RCS responsive cells in normal SJL lymph nodes prompted us to prepare a set of 21 RCS-specific T cell hybridomas. Like normal SJL T cells, these hybridoma cells respond to RCS, but not to normal syngeneic B cells; produce IL-2, IL-4, and IL-5; and promote growth of RCS in gamma-irradiated syngeneic hosts. A superantigen-like stimulation by RCS cells was borne out by the fact that all the RCS-specific hybridomas used V beta 16 in their TCR. RCS cells did not stimulate I-As-restricted, V beta 17a+ KLH-specific, or V beta 1+ heme-specific hybridomas, but were excellent Ag presents for these cells. Preincubation of RCS cells with high concentrations of the KM core peptide (high affinity for I-As) did not interfere with the ability of RCS to stimulate RCS-specific hybridomas. The relative representation of mRNA for V beta 1, 4, 10, 15, 16, and 17a was evaluated in RNA extracted from normal SJL lymph node cells responding to Con A or to RCS cells. Only V beta 16 was specifically enriched in the response to RCS. Moreover, the degree of responsiveness to RCS cells in lymph node cells from F1 hybrids of SJL and I-E transgenic SJL mice, corresponds to the relative abundance of V beta 16 in mRNA, but not of V beta 17a mRNA.

Syngeneic response to SJL follicular center B cell lymphoma (reticular cell sarcoma) cells is primarily in V beta 16+ CD4+ T cells

The growth of SJL B cell lymphomas (RCS, reticulum cell sarcoma) in vivo and in vitro is known to depend on cytokine production by RCS-responsive host CD4+ T cells. The high frequency of RCS responsive cells in normal SJL lymph nodes prompted us to prepare a set of 21 RCS-specific T cell hybridomas. Like normal SJL T cells, these hybridoma cells respond to RCS, but not to normal syngeneic B cells; produce IL-2, IL-4, and IL-5; and promote growth of RCS in gamma-irradiated syngeneic hosts. A superantigen-like stimulation by RCS cells was borne out by the fact that all the RCS-specific hybridomas used V beta 16 in their TCR. RCS cells did not stimulate I-As-restricted, V beta 17a+ KLH-specific, or V beta 1+ heme-specific hybridomas, but were excellent Ag presents for these cells. Preincubation of RCS cells with high concentrations of the KM core peptide (high affinity for I-As) did not interfere with the ability of RCS to stimulate RCS-specific hybridomas. The relative representation of mRNA for V beta 1, 4, 10, 15, 16, and 17a was evaluated in RNA extracted from normal SJL lymph node cells responding to Con A or to RCS cells. Only V beta 16 was specifically enriched in the response to RCS. Moreover, the degree of responsiveness to RCS cells in lymph node cells from F1 hybrids of SJL and I-E transgenic SJL mice, corresponds to the relative abundance of V beta 16 in mRNA, but not of V beta 17a mRNA.

Linkage of superantigen-like stimulation of syngeneic T cells in a mouse model of follicular center B cell lymphoma to transcription of endogenous mammary tumor virus

The MHC class II I-A(s) positive B cell lymphomas reticulum cell sarcoma (RCS) that arise in > 90% of SJL mice by the age of 12 months have superantigen-like stimulating properties. In the present study, therefore, RCS cell lines were examined for abnormal expression of endogenous mouse mammary tumor virus (MMTV) proviruses. Extraordinarily high expression of a 1.8 kb mRNA hybridizing with the long terminal repeat (LTR) of MMTV was found in both primary lymphomas and in vitro RCS lines, but not in an SJL B cell lymphoma, NJ101, that does not stimulate syngeneic T cells, or in LPS activated SJL B cells. A cDNA was cloned from cRCS-2 and sequenced. A 31mer oligonucleotide probe, prepared based on the unique C-terminal sequence of this RCS-Mtv LTR, detected the 1.8 kb mRNA in all RCS lymphomas, while a similar probe for the C-terminal sequence of Mtv-8 LTR hybridized with the larger mRNA present in normal B cells and in NJ101. Preincubation with 19mer antisense S-oligonucleotides, prepared based on the sequences of the first two potential translation initiation sites common to both Mtv-8 and the RCS-Mtv LTR, significantly reduced the ability of RCS cells to stimulate syngeneic T cells. Moreover, transfection of NJ101 cells with the cloned RCS-MMTV cDNA conferred V beta 16 T cell stimulating properties on to these cells. It is concluded that expression of the product of this MMTV-LTR mRNA provides RCS with the strong T cell stimulating properties that it needs for its growth. These results thus identify a novel oncogenic property of MMTV-LTR.

Protection against apoptosis in chicken bursa cells by phorbol ester in vitro

Like the thymus, the bursa of Fabricius is a site of massive lymphopoiesis accompanied by cell death in vivo. In the present study we have, therefore, examined whether chicken bursa and thymus cells exhibit apoptosis. Bursa and thymus cells from SC chickens, 4-10 weeks of age, were incubated for 8-24 hr with various reagents. Genomic DNA was isolated, electrophoresed in 3% Nusieve agarose gels, and examined for patterns of DNA fragmentation. A laddering of DNA in multiples of 200 base pairs, indicative of apoptosis, was observed particularly with bursa and, to a much smaller extent, with thymus or spleen cells. These patterns of DNA fragmentation from bursa cells could be prevented by adding phorbol myristate acetate (PMA) but not by its inactive analogue 4 alpha-PMA during culture. Ionomycin is not required for this effect and, alone, appears to be slightly toxic for bursa cells, although it does not inhibit the effect of PMA. PMA did not affect the degree of DNA fragmentation in spleen or thymus cells. The addition of the protein kinase C (PKC) inhibitor staurosporine abolished both the preventive effect of PMA on apoptosis and its protective effect on bursa cells, as assayed by [3H]thymidine incorporation 24-48 hr after the initiation of cultures. PKC inhibitors also prevented the proliferation-inducing effect of PMA + ionomycin on spleen cells. It is concluded that the activation of protein kinase C and perhaps other kinases protects against apoptosis in cultured bursa cells.