Evidence of alternative or concomitant use of perforin- and Fas-dependent pathways in a T cell-mediated negative regulation of Ig production.
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To study the possible involvement of perforin (Pfp)- and/or Fas-dependent cytotoxicity pathways in a T cell-mediated negative regulation of Ig production, we used the T cell-induced Ig-allotype suppression model. T splenocytes from Igha/a mice, when neonatally transferred into histocompatible Igha/b F1 or Ighb/b congenic hosts, are intrinsically able to totally, specifically, and chronically suppress the production of IgG2a of the Ighb haplotype (IgG2ab). It has not been established whether the suppression effectors, which are anti-IgG2ab MHC class I-restricted CD8+ T cells, cytolyse IgG2ab+ B targets or whether they only silence Ig production. In this study, using T cells from Igha/a Pfp+/+ or Pfpo/o mice, the latter obtained by crossbreeding, and B cells from Ighb/b Fas+/+ or Faslpr/lpr (lymphoproliferation) mice in appropriate adoptive transfer models, we demonstrated that: 1) under blockage of the Pfp-mediated pathway, Igha/a T cells were still able to induce suppression against wild-type IgG2ab+ B cells, 2) IgG2ab+ B cells with impaired Fas expression were also subjected to suppression by WT Igha/a T splenocytes, and 3) the suppression establishment was totally inhibited when both Pfp- and Fas-dependent mechanisms were simultaneously blocked, i.e., when Igha/a Pfpo/o T cells were used to induce suppression against Ighb/b Faslpr/lpr B cells. These results provide the first demonstration of the existence of alternative or simultaneous use of the major cytotoxic mechanisms in a T cell-mediated down-regulation of an Ig production. (+info)
Systemic viral interleukin-10 gene delivery prevents cartilage invasion by human rheumatoid synovial tissue engrafted in SCID mice.
(26/5787)
OBJECTIVE: To assess the effects of viral interleukin-10 (vIL-10) gene delivery on human rheumatoid synovial tissue. METHODS: SCID mice were engrafted subcutaneously with human rheumatoid synovial tissue and homologous cartilage before systemic injection of 10(9) plaque-forming units of type 5 E1a Elb-deficient non-replicative adenovirus vector containing the vIL-10 gene under control of the cytomegalovirus promoter (AdvIL-10; n = 10) or a control gene (AdvIL-10mut; n = 7). Three weeks later, the graft was removed for histologic analysis of cartilage invasion by synovial tissue. The number of CD3-positive mononuclear cells was assessed in the synovial tissue by immunohistology. Messenger RNA (mRNA) expression of matrix metalloproteinase 3 (MMP-3), tissue inhibitor of metalloproteinases 1 (TIMP-1), and proinflammatory cytokines was determined by polymerase chain reaction. RESULTS: Systemic vIL-10 gene transfer resulted in high sustained production of vIL-10 protein in SCID mouse sera (mean +/- SD 25 +/- 5 ng/ml on day 40 post vector injection). Moreover, vIL-10 mRNA expression was detected in the synovial tissue 3 weeks after intravenous injection of AdvIL-10, reflecting the gene transfer in the human graft. In animals treated with AdvIL-10, cartilage invasion by rheumatoid synovial tissue was significantly inhibited compared with the control vector (mean +/- SD histologic score 2.5 +/- 0.52 versus 0.75 +/-0.8; P < 0.0001). The number of T cells infiltrating the synovium and perichondral resorption in the animals treated with AdvIL-10 gene were not significantly modified relative to the control vector. In animals treated with AdvIL-10, the MMP-3-TIMP-1 balance was partially restored, independent of the effect on mRNA expression of tumor necrosis factor a, IL-1, IL-6, or IL-8. CONCLUSION: Systemic vIL-10 gene transfer prevented cartilage invasion by synovial tissue engrafted in SCID mice. This model offers the opportunity to study the biologic effects of gene transfer in vivo in rheumatoid synovium. (+info)
Traumatic wound rupture after penetrating keratoplasty in Africa.
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AIM: To investigate risk factors, visual outcome, and graft survival for traumatic wound rupture after penetrating keratoplasty. METHODS: A retrospective analysis of 336 patients who underwent penetrating keratoplasty from 1988 to 1995. RESULTS: 19 patients (5.7%) suffered traumatic postoperative wound rupture requiring surgical repair. They were younger (mean age 16.6 years, 95% CI 13.2-20.6) and more frequently keratoconic (p = 0.01) than other patients (mean age 28.9 years, 95% CI 26.-31.0). Mean postoperative follow up was 37.7 (SD 22.9) months and 24.5 (18.9) months for the rupture and non-rupture patients. Mean interval between keratoplasty and rupture was 18 (21) weeks. The lens was damaged and removed in 37% of ruptured eyes. For keratoconics, the probability of graft survival at 5 years was lower (p = 0.03) in the ruptured eyes (75%) than in the non-ruptured eyes (90%). Endothelial failure was a more common (p <0.05) cause of graft opacification in ruptured grafts than in intact grafts. Of the ruptured eyes, 53% achieved a final corrected acuity of at least 6/18 and 63% achieved at least 6/60 compared with 48% and 71% of the intact eyes respectively (both p >0.1). The proportion of keratoconic eyes which achieved at least 6/60 was lower (p = 0.02) in the ruptured eyes (67%) than the non-ruptured eyes (87%). Eyes with wound ruptures of 5 clock hours or greater were less likely (p <0.05) to achieve an acuity of 6/18 and were more likely (p <0.05) to have an associated lens injury. CONCLUSIONS: Graft rupture is relatively common in African practice, particularly in young keratoconics. Visual outcome and graft survival are not significantly worse than for other grafted eyes, but are significantly worse than for other grafted keratoconic eyes. (+info)
Survival of donor leukocyte subpopulations in immunocompetent transfusion recipients: frequent long-term microchimerism in severe trauma patients.
(28/5787)
We recently reported detection of a transient increase in circulating donor leukocytes (WBCs) in immunocompetent recipients 3 to 5 days posttransfusion (tx) (Blood 85:1207, 1995). We have now characterized survival kinetics of specific donor WBC subsets in additional tx populations. Eight female elective surgery patients (pts) were sampled pre-tx and on days 1, 3, 5, 7, and 14 post-tx. Ten female trauma pts transfused with a total of 4 to 18 U of relatively fresh red blood cells were sampled up to 1.5 years post-tx. WBC subsets from frozen whole blood were isolated using CD4, CD8 (T cell), CD15 (myeloid), and CD19 (B cell) antibody-coated magnetic beads. Donor WBCs were counted by quantitative polymerase chain reaction (PCR) of male-specific sex determining region (SRY) sequences. PCR HLA typing and mixed leukocyte reaction (MLR) between recipient and donor WBCs were performed on two of the trauma tx recipients who had long-term chimerism of donor cells post-tx. In 6 of 8 female surgery pts, circulating CD4(+) male donor cells peaked at day 3 or 5 (0.01 to 1 cell/microL), followed by clearance by day 14. In 7 of 10 female trauma pts, we observed multilineage persistence of male donor WBCs (CD4, CD8, CD15, CD19) for 6 months to 1.5 years post-tx at concentrations of 10 to 100 cells/microL. In 2 trauma recipients studied, MLR showed no, or very low, response to WBC of the single donor implicated as the source of microchimerism by HLA typing. Establishment of long-term multilineage chimerism in trauma recipients is probably caused by engraftment of donor stem cells and mutual tolerance between recipient and donor leukocytes. A better understanding of factors determining clearance versus chimerism of transfused leukocytes is critical to prevention of alloimmunization and transfusion-induced graft-versus-host disease, and, potentially, to induction of tolerance for transplantation. (+info)
Murine plasmacytomas, carrier of the t(12;15) chromosomal translocation, develop from immature/mature B cells not from differentiated plasma cells.
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Dysregulation of the c-myc gene by chromosomal translocation in >95% of murine plasmacytomas (MPCs) is an obligatory requirement for the transformation of B lymphocytes into MPCs. However, it is still unknown whether sIg+ B cells or differentiated plasma cells are the legitimate precursor cells from which MPCs develop. To address this question, C.B-17 scid/scid (SCID) mice were reconstituted with splenic surface Ig-positive (sIg+) B lineage cells originating from BALB/cRb6.15 (B/cRb6.15) or human IL-6 transgene-congenic BALB/cRb8.12 mice (B/cRb8.12 IL-6-Tg). Six of 80 SCID mice reconstituted with B/cRb6.15 sIg+ B cells developed MPCs after pristane (2,6,10,14-tetramethylpentadecane) treatment followed by Abelson murine leukemia virus (A-MuLV) infection (incidence 7.5%) and four of 40 after pristane treatment alone (incidence 10%). Similarly, in 20 SCID mice reconstituted with B/cRb8.12 IL-6-Tg splenic sIg+ B cells the MPC incidence was 10%. Karyotype analysis revealed that all the translocations were of typical t(12;15) type and all tumors carried the Rb6.15 or Rb8.12 marker chromosome, indicating their donor cell origin. In contrast, none of the 48 SCID mice reconstituted with plasma cells obtained from the lymph nodes of B/cRb8.12 IL-6-Tg mice developed MPCs when treated either with pristane plus A-MuLV (20 mice) or with pristane alone (28 mice), although the transferred plasma cells were still functional in the recipient SCID mice 6 months after transfer. The findings indicate that the malignant transformation triggered by Ig/myc juxtaposition occurs more in immature (sIgM+) and/or mature (sIgM+/sIgD+, sIgG+ and sIgA+) B cells than in differentiated G0 or cycling plasma cells. We inferred that immature and/or mature B cells and not differentiated plasma cells are most likely the principal source of precursor cells from which the typical t(12;15) MPCs develop. (+info)
Mice with Th2-biased immune systems accept orthotopic corneal allografts placed in "high risk" eyes.
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CD4+ T cells of the Th1 type play a central role in acute rejection of solid tissue grafts, including orthotopic corneal allografts. Th1 cells, which mediate delayed hypersensitivity, are the polar opposites of CD4+ Th2 cells, and the latter cells cross-regulate Th1 cells through the unique pattern of cytokines they secrete. As such, Th2 cells may have a useful role to play in preventing rejection of corneal allografts. To test this possibility, the immune systems of adult mice were biased toward Th2 responses by immunization with keyhole limpet hemocyanin plus IFA. When immunized subsequently with either OVA or allogeneic corneal tissue, these mice acquired Ag-specific primed T cells of the Th2 type. More important, allogeneic corneas grafted into neovascularized eyes of Th2-biased mice experienced significantly enhanced survival. To demonstrate that enhanced survival was promoted by donor-specific Th2 cells, lymphoid cells from keyhole limpet hemocyanin-immune mice bearing healthy corneal allografts suppressed orthotopic corneal allograft rejection when adoptively transferred into naive, syngeneic recipients. We conclude that acceptance of corneal allografts in neovascularized mouse eyes can be significantly enhanced by biasing the recipient immune system toward Th2 responses. (+info)
Relationship between chimerism and tolerance in a kidney transplantation model.
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The persistence of donor leukocytes in recipients of organ allografts has been associated with long-term graft acceptance. However, it remains unclear whether this peripheral donor cell microchimerism plays an active role in graft acceptance or is simply a consequence of the maintenance of sufficient immunosuppression to avoid rejection. A model of kidney transplantation between swine leukocyte Ag (SLA)-matched miniature swine, in which tolerance can be established with or without immunosuppressive treatment, has been used to study the correlation between donor leukocyte chimerism and kidney graft acceptance. SLA-identical kidney transplants were performed from animals positive for an allelic pig leukocyte Ag to animals negative for this marker. SLA-identical kidney transplant recipients given a 12-day course of cyclosporine (CyA) (n = 3) became tolerant, showing stable serum creatinine levels (1-2 mg/dl) after cessation of CyA treatment. Donor cell chimerism (0.2-0.7%) was present by FACS in all three animals with peak levels detected at 3 wk. Two control animals receiving SLA-identical kidney grafts without CyA also showed stable serum creatinine levels and became tolerant. However, in neither of these animals could donor leukocytes be detected in the peripheral blood beyond 1 wk following transplantation. In one additional control animal, ureteral obstruction occurred at day 10, and was associated with additional peripheral chimerism, presumably related to inflammation rather than to immune status. These results indicate that the persistence of donor cell chimerism is not a requirement for the maintenance of tolerance to organ allografts in this model. (+info)
Immunomodulatory functions of low-molecular weight hyaluronate in an acute rat renal allograft rejection model.
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Low molecular weight hyaluronate (LMW-HA) blocks interactions between T lymphocyte CD44 and hyaluronate (HA), a heteropolysaccharide that is expressed on the surface of endothelial cells and ubiquitously in the extracellular matrix. This study was undertaken to assess the ability of LMW-HA to modify the course of experimental acute renal allograft rejection. Lewis (LEW) rats were bilaterally nephrectomized and received an orthotopic, fully MHC-mismatched, Wistar-Furth (WF) kidney transplant. Animals received either no treatment, low doses of cyclosporin A (CsA) on days 0 to 5, LMW-HA on days 0 to 5, or CsA plus LMW-HA on days 0 to 5 after transplantation. With no treatment, CsA monotherapy, or HA monotherapy, animals rejected their allografts at a median of 15, 13, and 7.5 d, respectively (P = NS). In contrast, combined CsA plus LMW-HA therapy prevented acute rejection and significantly prolonged graft survival (P = 0.008) to a median of 49.0 d. CsA/LMW-HA-treated grafts also demonstrated better preservation of renal function at day 30 (serum creatinine level, 1.38+/-0.8 mg/dl), compared with surviving animals treated with CsA alone (2.9+/-0.55 mg/dl, P<0.05). Histologic graft analysis of CsA/LMW-HA-treated animals at day 7 after transplantation showed minimal rejection and leukocyte infiltration, compared with all other groups. Intragraft gene expression analysis, using semiquantitative reverse transcription-PCR, at the same time point showed reductions of CD4, CD8, and interferon-gamma transcript levels in the combined-treatment group. This is the first study demonstrating the immunomodulatory functions of LMW-HA in vivo in the setting of organ transplantation. Defining the exact mechanisms that underlie this immunomodulation may provide the rationale to develop novel strategies for use in clinical transplantation. (+info)