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K D Chavin

Publications and source records attributed to K D Chavin.

At least 37 records · Page 2Linked to original sources
PubMed1995

Multiple vectors effectively achieve gene transfer in a murine cardiac transplantation model. Immunosuppression with TGF-beta 1 or vIL-10.

The application of gene transfer techniques to organ transplantation offers the potential for modulation of immunity directly within an allograft without systemic side effects. Expression vectors and promoter elements are important determinants of gene transfer and expression. In this study, various vectors (naked plasmid DNA, retroviral vector, herpes simplex viral vector, and adenoviral vector) with various promoters (RSV-LTR, SV40, MuLV-LTR, HCMVie1) were directly compared to demonstrate the successful gene transfer and expression of beta-galactosidase in murine myoblasts in vitro and within murine heterotopic, nonvascularized cardiac isografts or allografts in vivo. Expression of transferred genes was not toxic to cells and strength of expression varied according to the type of vector. Plasmid DNA was expressed in myocytes, retroviral vector was expressed in the graft infiltrating cells, and herpes simplex and adenoviral vectors were expressed in both myocytes and graft-infiltrating cells. Preliminary studies evaluated the ability of these vectors to deliver immunologically important signals. Allografts injected with pSVTGF-beta 1, a plasmid-encoding transforming growth factor beta 1 (TGF-beta 1) under the control of the SV40 promoter, showed significant prolongation of graft survival of 26.3 +/- 2.5 days compared with 12.6 +/- 1.1 days for untreated allografts, and 12.5 +/- 1.5 days for the allografts injected with control plasmid (P < 0.05). Allografts injected with MFG-vIL-10, a retroviral vector encoding viral interleukin-10 under the control of the MuLV-LTR, showed prolongation of graft survival of 36.7 +/- 1.3 days versus 12.6 +/- 1.1 days for the untreated allograft, and 13.5 +/- 2.0 days for the allografts injected with control retroviral vector (P < 0.001). Both vectors were transcriptionally active in vivo and did not appear to have toxic effects. Gene therapy for transplantation can induce transient expression of immunologically relevant molecules within allografts that impede immune activation while avoiding the systemic toxicity of conventional immunosuppression.

Animals↗
PubMed1995

CD3 and CD2 ligation alters CD49d epitope expression.

The combination of anti-CD2 plus anti-CD3 monoclonal antibodies (mAbs) synergistically prolongs allograft survival and induces antigen-specific tolerance. Since altered expression of cell surface molecules might be important for tolerance induction, the effect of anti-CD2 and anti-CD3 mAbs on the expression of adhesion molecules was analyzed on splenic T cells with an in vitro model. The anti-CD2 mAb, 12-15, alone had no effect on the expression of integrin alpha 4-chain epitopes recognized by two anti-CD49d (VLA-4 alpha) mAbs, R1-2 and PS/2. The anti-CD3 mAb, 2C11, caused R1-2 epitope expression to decrease, while PS/2 epitope expression remained unchanged. The combination of anti-CD2 and anti-CD3 mAbs further decreased R1-2 epitope expression while preserving PS/2 epitope expression. The expression of integrin beta 1 and beta 7 chains, each of which form heterodimers with alpha 4 chains, also remained unchanged. Expression of other integrin, selectin, or immunoglobulin superfamily molecules (CD11a, CD18, CD44, CD45, CD48, CD54 and CD62L) were all significantly increased by anti-CD2 or anti-CD3 mAbs. Decreased R1-2 epitope expression was anti-CD3 dependent and specifically augmented by anti-CD2 mAb. CD2-regulated decreases in R1-2 epitope expression correlated with increased cAMP and could be prevented by addition of high doses of IL-2 but was not affected by the addition of other cytokines. R1-2 alpha 4 epitope expression could be specifically restored by the divalent cation Mn2+, which also increased functional binding to the VCAM-1 ligand. Significantly, the R1-2 but not the PS/2 mAb prolonged graft survival in a cardiac allograft model. These results show that anti-CD2 and anti-CD3 mAbs selectively decrease integrin alpha 4 chain epitope expression on T cells through conformational regulation. Decreased expression of a CD49d epitope is unique in comparison to the up-modulation of other T-cell adhesion receptors. These changes correlate with functional effects and provide an additional mechanistic explanation for the synergistic effect of anti-CD2 plus anti-CD3 in producing tolerance.

Animals↗
PubMed1995

Increased cAMP and cAMP-dependent protein kinase activity mediate anti-CD2 induced suppression of anti-CD3-driven interleukin-2 production and CD25 expression.

Anti-CD2 monoclonal antibody (mAb) can act synergistically with anti-CD3 to produce tolerance and diminish the anti-CD3-induced cytokine syndrome. Since interleukin(IL)-2 production and IL-2 receptor (IL-2R; CD25) expression are important determinants of CD3-driven T cell activation, the effects of anti-CD2 on anti-CD3-induced CD25 expression and IL-2 production were analyzed and related mechanistically to CD2-stimulated cAMP signaling with an in vitro model of T cell activation. The anti-CD2 mAb, 12-15, alone had no effect on splenic T cell CD25 expression and IL-2 production, while the anti-CD3 mAb, 145-2C11, caused significant increases in both CD25 expression and IL-2 production. The addition of anti-CD2 inhibited anti-CD3-induced increases in CD25 and IL-2. The inhibitory signal delivered by anti-CD2 was effective in many forms of T cell activation, since other stimuli which increased CD25, such as concanavalin A, phytohemagglutinin, and Staphylococcal enterotoxin B (SEB), could also be inhibited by anti-CD2. The inhibitory effect of anti-CD2 on CD25 could not be reversed by high doses of supplemental IL-2 added to the culture. Anti-CD2 increased cytoplasmic cAMP in a dose- and time-dependent manner. Reagents that increased cytoplasmic cAMP such as forskolin, cholera toxin, and 3'-isobutyl-1-methylxanthine could mimic the inhibitory effect of anti-CD2 on anti-CD3-driven CD25 expression. Anti-CD2 also increased the activity of cAMP-dependent protein kinase (PKA). H8, a PKA antagonist, blocked the inhibitory effect of anti-CD2 on CD25 expression, further confirming the role of PKA in CD2-induced negative signaling. The use of paired agonists to PKA demonstrated that a type I PKA was the preferential enzyme isoform stimulated by CD2 ligation. These findings show that increased cAMP and PKA activity mediate anti-CD2-induced suppression of anti-CD3-driven IL-2 production and CD25 expression, and provide mechanisms for anti-CD2-induced immunosuppression and inhibition of the cytokine syndrome associated with anti-CD3 treatment.

Animals↗
PubMed1994

CTLA4Ig prolongs allograft survival while suppressing cell-mediated immunity.

T cell activation is the result of antigen-specific interactions with the TCR/CD3 complex and costimulation via other T cell surface receptors. Prevention of costimulation can result in clonal anergy. CTLA4Ig is a fusion protein that binds with high-affinity to the B7/BB1 ligand and blocks the interaction of this ligand with CD28 and CTLA4. We explored the immunosuppressive effects of CTLA4Ig in a murine nonvascularized heterotopic cardiac transplant model and in a model of cell mediated immunity. CTLA4Ig administered in vivo for two days at the time of transplantation resulted in significant prolongation of allograft survival (55 +/- 2.0 vs. 12.2 +/- 0.5 days for control, P < 0.03). Administration at later times or to previously primed animals produced no prolongation of graft survival. CTLA4Ig administered during in vivo immunization to the hapten TNP suppressed the contact sensitivity response and inhibited the subsequent in vitro generation of secondary TNP-specific CTL. CTLA4Ig administered in vivo had no effect on subsequent primary alloantigen-specific CTL or MLR responses--however, when added to culture the fusion protein inhibited the MLR response by 80%, but not the alloantigen-specific CTL response. CTLA4Ig inhibited CD4+ and CD8+ proliferative and cytokine responses to alloantigen. Flow cytometry showed no changes in distribution of subpopulations of T cells. These results confirm the immunosuppressive activity of CTLA4Ig in vivo in an allograft model and show that both CD4+ and CD8+ T cells are suppressed by CTLA4Ig. The most efficacious time of administration is during priming of the immune response at the time of antigen presentation.

Abatacept↗
PubMed1994

Anti-CD2 mAbs suppress cytotoxic lymphocyte activity by the generation of Th2 suppressor cells and receptor blockade.

The mechanism by which anti-CD2 mAbs inhibit hapten-specific and alloantigen specific CTL was explored. In vivo administration of alpha-CD2 mAbs resulted in 80 to 100% inhibition of alloantigen specific CTLs. Mixing cells from control animals with cells from alpha-CD2-treated groups demonstrated transferable suppression of CTL (40-67% suppression). These suppressor cells were CD4+CD8- and associated with increased IL-4 and TGF-beta in culture as compared with controls. Anti-CD2 mAbs added at the initiation of culture resulted in 60 to 72% inhibition of trinitrophenyl-CTL, whereas mAbs added at the time of assay resulted in less than 50% inhibition of trinitrophenyl-CTLs. F(ab')2 and Fab alpha-CD2 produced inhibition similar to intact mAbs when added at the time of the lytic assay, whereas both produced only modest inhibition in vivo or when added at the initiation of culture. Alloantigen-specific CTLs were not affected by Ab addition to either culture or assay. The immunosuppressive effects were generalizable because a panel of alpha-CD2 mAbs were all comparably effective in suppressing hapten-specific CTLs when administered in vivo. The results demonstrate that the inhibitory effects are the result of blockade of receptor adhesion function during Ag priming or target recognition, Fc-related effects, and the generation of a negative regulatory, CD4+CD8-, IL-4- and TGF-beta-producing TH2 suppressor T cell.

Animals↗
PubMed1994

Anti-CD2 monoclonal antibodies synergize with FK506 but not with cyclosporine or rapamycin to induce tolerance.

CsA, FK506, and rapamycin prolong allograft survival; however, each has significant associated side effects at therapeutic doses. Anti-CD2 mAbs also prolong survival but without toxicity. We tested whether alpha CD2 mAbs in combination with subtherapeutic immunosuppression could prolong allograft survival in a synergistic fashion. C57BL/6 (H-2b) mouse hearts were transplanted to CBA (H-2k) mice in a heterotopic, non-vascularized cardiac allograft model. Recipients received immunosuppressants intraperitoneally for 14 days and/or alpha CD2 mAb intravenously for 2 days starting at the time of grafting. Survival was determined by electrocardiogram monitoring. Anti-CD2 alone prolonged survival to 22.4 +/- 1.0 days versus 13.4 +/- 0.5 days for untreated controls (P < 0.05), while low dose FK506 minimally prolonged survival to 16.7 +/- 0.7 days (P < 0.057). However, FK506 plus alpha CD2 resulted in synergistic prolongation of graft survival to 28.0 +/- 2.1 days. Several doses of CsA and rapamycin in combination with alpha CD2 did not prolong survival over alpha CD2 administered alone. A 60-day course of low dose FK506 plus alpha CD2 resulted in indefinite graft survival (> 165 days). These animals were tolerant since they accepted a second donor-specific graft. CTL and MLR activity in long-term recipients were normal to both donor-specific and third party alloantigen. The combination of alpha CD2 with low dose FK506 is synergistic in prolonging cardiac allograft survival, while combinations with CsA and rapamycin are not. Continuous administration of low dose FK506 plus alpha CD2 results in a state of tolerance. This suggests that FK506 acts at a different locus in allograft immunity compared with the other immunosuppressants and this may be related to the alternative CD2 T cell activation pathway.

Animals↗
PubMed1994

Anti-CD2 receptor and anti-CD2 ligand (CD48) antibodies synergize to prolong allograft survival.

Indefinite graft survival was obtained with murine cardiac allografts using the combined administration of monoclonal antibodies (mAbs) directed against the receptor ligand pair CD2-CD48. Although each antibody could prolong graft survival when given alone, neither resulted in the indefinite graft survival seen with the combination. Combined mAb administration is associated with inhibition of T cell priming and help and subsequent cytotoxic T lymphocyte generation. This indicates that the interaction between CD2 and its ligand is important for antigen priming and recognition, and combined mAbs may prove to be a useful therapeutic regimen for transplantation.

Animals↗
PubMed1994

Production of multiple murine CD2 receptor constructs using the baculovirus expression vector and a rapid dot-blot assay.

The baculovirus expression system was used to produce three different constructs of the murine cell surface adhesion receptor CD2. One construct coded for a single, N-terminal, Ig-fold domain. It was inefficiently secreted and therefore primarily intracellular. The second construct coded for both extracellular, N-terminal Ig-fold domains. This was efficiently secreted into culture supernatant. The third construct coded for the full-length transmembrane molecule which localized to the cell surface. All constructs were monomers of predicted MWr and were appropriately glycosylated. They retained epitopic specificity as demonstrated by binding to mAbs, and adhesion function as demonstrated by a rosetting assay.

Animals↗
PubMed1994

Anti-CD48 (murine CD2 ligand) mAbs suppress cell mediated immunity in vivo.

With the identification of murine CD48 as a homolog of the human CD2 ligand LFA-3 (CD58) and as a ligand itself for murine CD2, the anti-murine CD48 mAb HM48-1 was administered intravenously to investigate the role of CD48 in cell mediated immunity in vivo. Anti-CD48 mAb diminished the contact sensitivity response to the hapten trinitrophenol (TNP). mAb also inhibited in vivo priming for the subsequent generation of secondary, TNP-specific, cytotoxic T lymphocytes (CTL) in vitro. The inhibitory effect was most effective in the afferent or inductive phase of immunity for CTL, while anti-CD48 mAb was most inhibitory for the efferent or elicitative phase of contact sensitivity. Addition of anti-CD48 mAb directly to secondary CTL cultures also completely inhibited CTL generation, while addition to the lytic assay showed only minimal inhibition of CTL activity. Combining cells from mAb treated and untreated animals showed no evidence for suppressor cells. Further experiments revealed that mAb administered in vivo, as well as to culture, inhibited development of primary, alloantigen-specific CTL in vitro. Mixed lymphocyte reaction and phytohemagglutinin proliferation were partially suppressed by mAb administered in vivo or in vitro, whereas other mitogenic responses remained unaffected. Flow cytometric analysis revealed a moderate down modulation of CD48, CD3 and CD8 after treatment with anti-CD48. However, this did not represent T cell depletion since CD2, Thy-1.2 and Ig expression did not change. These results support a major unrecognized role for CD48 in diverse aspects of cell mediated immunity, affecting both CD4+ and CD8+ effector T cell function.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Gene transfer for transplantation. Prolongation of allograft survival with transforming growth factor-beta 1.

OBJECTIVE: The authors tested the ability of plasmid gene transfer to express transforming growth factor-beta 1 (TGF-beta 1), prolong allograft survival, and evaluate promoter effects on gene expression. SUMMARY BACKGROUND DATA: Delivery of immunosuppressants directly to allografts using gene transfer and gene therapy approaches may inhibit immune activation while avoiding the systemic toxicity of conventional immunosuppression. Candidate genes include soluble cytokines, which could be expressed at low levels throughout the graft while inducing a local immunosuppressive effect. Transforming growth factor-beta 1 is a soluble cytokine that has pleiotropic immunosuppressive effects. METHODS: Cardiac grafts from syngeneic (CBA/J, H-2k) or allogenic (C57BL/6, H-2b) donors were placed into CBA/J recipients. Purified plasmid DNA-encoding murine TGF-beta 1 or beta-galactosidase (Lac Z) under the control of RSV, SV40, MMTV, or pancreatic elastase promoters was injected into grafts at surgery. The Lac Z expression was determined by histologic examination and TGF-beta 1 expression by graft survival. Cytotoxic T lymphocyte and flow cytometric analyses were performed to evaluate the immunosuppressive effects of TGF-beta 1 in vitro. RESULTS: Plasmid DNA-encoding TGF-beta 1 prolonged survival from 12.6 +/- 1.1 days to 26.3 +/- 2.5 days (p < 0.02, Student's t test). The SV40 promoter was superior to the MMTV promoter in its ability to prolong survival. The effects of the plasmids were specific because Lac Z, antisense TGF-beta 1 inserts, or pancreatic elastase promoter did not prolong allograft survival. Histologic examination demonstrated Lac Z expression at least 14 days post-transplant in myocardial cells. Both RSV and SV40 promoters were effective in this respect, while a control null promoter was not. Toxicity testing showed that gene transfer of TGF-beta 1 did not alter survival or histology of syngeneic grafts. In addition, plasmids and purified TGF-beta 1 protein were not toxic to myoblasts in vitro. Recombinant TGF-beta 1 inhibited cytotoxic T lymphocyte generation and altered T cell surface receptor expression and subset expansion in vitro. CONCLUSION: Gene transfer/therapy with plasmid DNA encoding TGF-beta 1 in vivo achieves immunologic effects that prolong allograft survival. Multiple promoters effectively induce plasmid expression, which is achieved in cardiac myocytes for at least 2 weeks without toxicity or adverse systemic effects. Transforming growth factor-beta 1 inhibits immune responses by different mechanisms, revealed by in vitro analysis of T cell cytolytic function, subset distribution, and receptor display.

Animals↗
PubMed1993

Combined anti-CD2 and anti-CD3 receptor monoclonal antibodies induce donor-specific tolerance in a cardiac transplant model.

Administration of mAb against either the CD2 or CD3 receptor prolongs graft survival in CBA recipients in a heterotopic, nonvascularized cardiac transplant model, whereas the combination of mAb produces indefinite survival. Combined alpha-CD2 plus alpha-CD3 mAb synergistically prolonged allograft survival indefinitely for C57BL/6 donor hearts (> 150 vs 13.4 +/- 0.5 days for controls, p < 0.001, Wilcoxon's sign rank). All second donor-specific C57BL/6 allografts survived > 100 days (p < 0.001) without any additional immunosuppression. Third-party BALB/c allografts were rejected in a first set fashion (14.2 +/- 0.5 days). Anti-CD2 mAb of other epitopic specificities and isotypes demonstrate equivalent immunosuppressive capacity. The combination of mAb resulted in indefinite graft survival in other strain combinations. Therefore, these results are not restricted to a particular alpha-CD2 mAb or MHC combination. Combinations of alpha-CD2 plus mAb with specificities other than to CD3 did not result in tolerance, showing that the CD2-CD3 interaction was critical for tolerance induction. CTL and MLR responses from tolerant animals were normal both to H-2b and H-2d stimulators, indicating that clonal deletion of effector T cells did not occur. Adoptive transfer of naive recipient type cells broke tolerance, showing that graft adaptation was not the major determinant of tolerance maintenance. Flow cytometric analysis demonstrated that tolerance was not associated with deletion of T cells. The results imply that the mechanism of tolerance induction is related to suppression and/or anergy of helper and effector cells at the time of allografting, whereas maintenance of tolerance is associated with anergy in the Th cell compartment.

Animals↗
PubMed1993

Production and characterization of soluble and transmembrane murine CD2. Demonstration that CD48 is a ligand for CD2 and that CD48 adhesion is regulated by CD2.

The baculovirus expression vector was used to produce full length, two amino-terminal Ig-like extracellular domains, and one amino-terminal Ig-like extracellular domain soluble murine CD2 products. The products were monomeric, glycosylated, and of the correct predicted m.w. Sf9 insect cells infected with recombinant baculovirus encoding the full length construct display cell surface CD2 by flow cytometry and rosette with murine cell lines that express the ligand for CD2. Uninfected Sf9, wild-type baculovirus-infected Sf9, and Sf9 expressing truncated products do not display cell surface CD2 nor do these latter Sf9 bind to murine cell lines. Cell binding is inhibited by anti-CD2 mAb. All CD2 products possess ligand binding activity since purified preparations of these block cell adhesion. All CD2 antigenic epitopes are close to the ligand binding site because all mAb tested can inhibit cell adhesion. The ligand for CD2 is shown to be CD48. Only CD48+ cell lines can bind CD2+ Sf9 and this is inhibited by anti-CD48 mAb. Antibodies against the closely related cell surface Ag Ly-6A.2 and Ly-9.2 do not inhibit binding. Purified, soluble CD2 also inhibits the binding of anti-CD48 mAb to the cell surface. Unexpectedly, additional mAb blocking studies show that CD2 on the surface of CD48+ cell lines influences adhesion to CD2+ binding partners. The use of cells expressing CD2 and/or CD48 provides evidence for a cis CD2-CD48 interaction on the cell surface in which CD2 negatively regulates CD48 adhesion properties.

Animals↗
PubMed1993

Combination anti-CD2 and anti-CD3 monoclonal antibodies induce tolerance while altering interleukin-2, interleukin-4, tumor necrosis factor, and transforming growth factor-beta production.

OBJECTIVE: These studies were designed to elucidate the mechanism by which signals delivered by anti-CD2 monoclonal antibody (MoAb) interfere with activational signals delivered by anti-CD3 MoAb and induce long-term graft survival and tolerance. SUMMARY BACKGROUND DATA: Anti-CD2 or anti-CD3 MoAb can prolong allograft survival when administered alone. In combination, they synergistically prolong survival while reducing anti-CD3-associated cytokine toxicity. It was postulated that the mechanism of synergism and reduced cytokine toxicity was related to anti-CD2-induced alterations in anti-CD3-induced T-cell activation. METHODS: C57BL/6 (H-2b) mouse hearts were transplanted to CBA (H-2k) mice. The recipients received anti-CD2 and/or anti-CD3 MoAb intravenously only at the time of initial allografting. Serum from treated animals and culture supernatants from lymphocytes stimulated in vitro with anti-CD3 were examined for interleukin (IL)-2, -4, -6, and -10, tumor necrosis factor (TNF), and transforming growth factor-beta (TGF beta). RNA was isolated from lymphocytes from treated animals and examined for receptor and cytokine gene expression by northern hybridization or reverse transcribed and amplified by the polymerase chain reaction (PCR). RESULTS: Anti-CD2 and anti-CD3 MoAbs alone prolonged graft survival (22.0 +/- 0.5 days and 28.0 +/- 0.5 days, respectively; p < 0.02 and p < 0.01 vs. control, by Wilcoxon signed-rank test). Combined anti-CD2/anti-CD3 MoAbs synergistically prolonged survival indefinitely (> 150 days, p < 0.01) while decreasing cytokine toxicity. Second donor-specific allografts also showed long-term survival. The peak serum TNF concentration (2100 units/mL) was reduced 78% by anti-CD2 treatment (455 units/mL). Anti-CD2 inhibited anti-CD3-stimulated proliferation and in vitro production of IL-2 and IL-4, with no alteration of IL-6, IL-10, or TNF. Conversely, there was an increase in the immunosuppressive cytokine TGF beta. PCR analysis showed that anti-CD2 reduced anti-CD3-stimulated IL-2 messenger RNA expression, and by northern analysis, anti-CD2 inhibited anti-CD3-stimulated increases in messenger RNA for the CD2 and CD3 receptors themselves. CONCLUSIONS: The combination of anti-CD2 and anti-CD3 MoAbs induced a state of tolerance while decreasing anti-CD3-associated cytokine toxicity. The mechanism was related to anti-CD2-generated alterations in T-cell activation and gene expression.

Animals↗
PubMed1993

Anti-CD2 and anti-CD3 monoclonal antibodies synergize to prolong allograft survival with decreased side effects.

Anti-CD3 monoclonal antibody suppresses immunity and prolongs allograft survival; however, it induces T cell activation and overproduction of soluble factors that result in a deleterious cytokine syndrome. Anti-CD2 mAb also prolongs allograft survival, by suppression of mature and precursor CD4 and CD8 T cells and NK cells, without an associated cytokine release. Because of the close physical and functional association of CD2 and CD3 on the T cell surface, we tested whether alpha CD2 mAb in combination with alpha CD3 mAb could act synergistically to prolong allograft survival, and whether the combination would affect the alpha CD3-associated cytokine syndrome. C57BL/6 (H-2b) hearts were transplanted to CBA (H-2k) recipients in a heterotopic nonvascularized model. Recipients received alpha CD2 (12-15) or alpha CD3 (145-2C11) mAb i.v. alone or in combination. Lymphocytes from treated animals were also analyzed by fluorescent flow cytometry and stimulated in vitro and assessed for proliferation and lymphokine production. Anti-CD2 and alpha CD3 each prolong allograft survival (mean survival time 22.4 +/- 1.0 and 27.4 +/- 3.3 days, respectively vs. 14.0 +/- 0.6 for control mAb, P < 0.001 for both vs. control). Combinations of mAbs show a more complicated interaction. Very low doses (1 microgram) of alpha CD2 and alpha CD3, which have no effect when given alone, are synergistic (16.5 +/- 1.3 days, P < 0.02). A high dose of alpha CD2 (100 micrograms), which is immunosuppressive, is additive with a moderate dose of alpha CD3 (10 micrograms), which is immunostimulatory. The two mAbs are again synergistic when a high dose of alpha CD2 (100 micrograms) is combined with a high dose of alpha CD3 (1 mg) (> 51.5 +/- 23.0 days, P < 0.001). Furthermore, high-dose alpha CD2 administered 48 h prior to high-dose alpha CD3 was a more effective combination for prolonging allograft survival than both antibodies administered simultaneously (67.1 +/- 10 vs. 35.8 +/- 0.7 days, P < 0.05). Anti-CD2 also diminishes the alpha CD3-associated cytokine syndrome, and prior in vivo treatment with alpha CD2 decreases the subsequent in vitro proliferative response to alpha CD3 and the alpha CD3-stimulated production of IL-2 and IL-4. Flow cytometry demonstrates that in general these mAbs do not deplete but leave T cell populations intact with altered receptor expression. These results show that the combination of alpha CD2 and alpha CD3 mAbs prolongs cardiac allograft survival in a synergistic fashion while decreasing the side effects of alpha CD3 mAb alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Anti-tumor necrosis factor antibodies suppress cell-mediated immunity in vivo.

Rabbit anti-murine TNF-alpha antibodies were administered in vivo to mice to evaluate the role of TNF-alpha in T cell-mediated immunity. Anti-TNF suppressed the in vivo development of contact sensitivity to the hapten TNP in a dose-dependent fashion. Similarly anti-TNF suppressed the in vivo priming for TNP-specific CTL. Control antibodies did not suppress cell-mediated immunity, whereas purified murine rTNF-alpha neutralized the antibody activity. Antibody therapy was effective during the afferent or priming limb of immunity, but could not inhibit the response if administered during the efferent limb. FACS for CD2, CD3, CD4, and CD8 T, B, and NK cell surface markers demonstrated no major change in the distribution of splenic lymphoid cell populations in animals pretreated with anti-TNF antibody. These results suggest that anti-TNF antibody may be interfering with soluble cytokines rather than with cell surface TNF causing depletion of cell populations. In vitro analyses also showed that anti-TNF has minimal inhibitory effects on secondary (secondary CTL) or strong primary (primary CTL, alpha CD3, MLR) responses, even though these in vitro cultures produce TNF mRNA as shown by polymerase chain reaction amplification. Although anti-TNF antibody did not affect the above responses, primary interactions are strongly inhibited in vivo. These findings suggest that TNF is important during afferent, priming events in immunity and that inhibition of TNF receptor-ligand interactions may alter immunity early in a response. Conversely such inhibition is ineffective later in a response, perhaps due to the ability of multiple other receptor-ligand pathways to bypass TNF.

Animals↗
PubMed1992

Prolongation of allograft and xenograft survival in mice by anti-CD2 monoclonal antibodies.

Anti-CD2 monoclonal antibodies (mAb) were used to influence graft survival in two transplantation models. Xenogeneic rat islets were transplanted intraportally into mice. Anti-CD2 mAb prolonged xenograft survival and was synergistic with UVB irradiation in prolonging survival. Anti-CD2 mAb was also more potent than an anti-CD4 mAb in this model. Allogeneic cardiac grafts were transplanted across an entire H-2 difference and anti-CD2 mAb prolonged allograft survival in a dose-dependent fashion. Kinetic experiments revealed that anti-CD2 mAb was most potent when administered at the time of allografting. A delay in administration of mAb markedly reduced its immunosuppressive effects. Furthermore, additional doses of mAb given after the initial doses provided no increased immunosuppression and anti-CD2 mAbs did not delay rejection of second-set allografts. These findings support the notion that anti-CD2 mAbs interfere with afferent immunity and that CD2 is most important during the initial steps of an immune response. Investigation of the effect of anti-CD2 mAb on cellular immune functions demonstrated, in agreement with previous results, that it caused antigenic down-modulation of CD2 with relative sparing of CD3, CD4, and CD8 cell surface expression. Concomitantly the MLR, CTL, and NK responses were suppressed.

Animals↗