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N L Thai

Publications and source records attributed to N L Thai.

9 recordsLinked to original sources
PubMed1997

Interleukin-2 and interleukin-12 mediate distinct effector mechanisms of liver allograft rejection.

Interleukin-2 (IL-2), interleukin-12 (IL-12) or interleukin-4 (IL-4) were administered postoperatively to otherwise spontaneously accepting mouse liver allograft recipients (C57BL/10-->C3H) to test whether TH1 cytokines are critical mediators of rejection in this model. The induction of rejection at days 5 to 7 by exogenously administered IL-2 and IL-12, but not IL-4, suggests that mouse liver allograft rejection can be induced by TH1 cytokines; however, there appeared to be differences in the mechanism by which these cytokines induce liver rejection. IL-2 administration was accompanied by an increased intragraft infiltration of CD4+ and CD8+ cells and an up-regulation of natural killer (NK), lymphokine-activated killer (LAK), allospecific cytotoxic killer (CTL) activity and perforin mRNA when compared with media-treated controls. In contrast, exogenous IL-12 treatment was associated with a suppression of CTL, NK, and LAK activity compared with controls but an enhanced infiltration of F4/80+ macrophages as determined by immunohistochemistry. Determination of cytokine mRNA profiles by semi-quantitative reverse transcription polymerase chain reaction showed the up-regulation of interferon (IFN)-gamma, IL-4, IL-6, and IL-10 mRNA with IL-2 treatment when compared with media-treated controls. Interestingly, IL-2 mRNA was down-regulated in these animals, suggesting a negative feedback mechanism in IL-2 regulation. IL-12 treatment resulted in the up-regulation of IFN-gamma, IL-6, and IL-10 mRNA, but not IL-2 or IL-4 mRNA. Higher complement-directed cytotoxic antibody titers were seen in IL-12-treated recipients compared with controls, whereas IL-2 treatment showed no apparent differences in antibody titers compared with media treatment. These in vivo observations were mimicked in a mixed leukocyte reaction by supplementing the reaction with IL-2, IL-12, or media. These results suggest that rejection of mouse liver allografts may involve more than one distinct cellular immunological effector mechanism. One is mediated by IL-2 and appears to favor alloreactive CTL, whereas the other pathway is mediated by IL-12/IFN-gamma and involves macrophages and cytotoxic antibodies largely resembling a delayed-type hypersensitivity reaction.

Animals↗
PubMed1996

Second-set rejection of mouse liver allografts is dependent on radiation-sensitive nonparenchymal cells of graft bone marrow origin.

Livers are accepted spontaneously when transplanted orthotopically from B10 (H2b) or BALB/c (H2d) to C3H (H2k) mice without host immunosuppression. Presensitization to donor can, however, be induced by skin grafting two weeks prior to liver transplantation, resulting in second-set or "accelerated" liver graft rejection, within 4-5 days. In this study, the role of liver nonparenchymal cells (NPC) in second-set rejection was tested by donor whole-body irradiation and replacement of donor B10 liver NPC with those of either third-party (BALB/c) or recipient strain (C3H) bone marrow. Irradiation alone (9.5 Gy) of normal B10 donors before liver transplantation significantly prolonged graft survival in presensitized C3H recipients. Three months after bone marrow transplantation (BMT), chimeric livers expressing third-party or recipient haplotype, were transplanted orthotopically into unmodified C3H recipients. Graft survival was prolonged significantly compared with livers from normal or syngeneically reconstituted B10 donors. Prolonged survival of chimeric (BALB/c->B10) livers was also evident in C3H mice presensitized to alloantigens expressed on both the liver parenchymal (B10) and third-party NPC (BALB/c) by simultaneous grafting of skin from each donor strain. Determination of graft cytokine mRNA profiles 4 days posttransplant showed that replacement of donor with third-party or recipient strain BM-derived cells was associated with reduced expression of IL-2 and IFN-gamma mRNA compared with that in grafts from syngeneically reconstituted donors. IL-10 transcripts, however, were not significantly affected. The results are consistent with a key role of radiation-sensitive, donor-specific NPC of bone marrow origin in second-set liver rejection in presensitized hosts. In this process, competent donor-strain NPC appear to augment the activity of primed T cells responsible for the second-set rejection.

Animals↗
PubMed1995

Cytokine mRNA profiles in mouse orthotopic liver transplantation. Graft rejection is associated with augmented TH1 function.

Although mouse liver allografts are spontaneously accepted without immunosuppression in many strain combinations, rejection can be induced by presensitization with a donor skin graft two weeks prior to transplantation. In this study, the semiquantitative reverse transcription polymerase chain reaction (RTPCR) was used to assess the involvement of T helper (TH) cell subsets in liver allograft acceptance by determining cytokine mRNA in the graft and spleen of recipients with (A) spontaneously accepting allografts (B) rejecting liver allografts after previous skin sensitization, and (C) syngeneic controls. Spontaneously accepted liver allografts showed upregulation of TH1 (IL-2, IFN-gamma) and TH2 (IL-4, IL-10) intragraft cytokine mRNA, which peaked at day 6 and tapered off thereafter, when compared with levels in syngeneic grafts, but both IFN-gamma and IL-10 mRNA persisted up to day 30. This cytokine mRNA profile correlated with the transient intragraft inflammation associated with spontaneously resolving rejection. Presensitized recipients that rejected their grafts revealed marked upregulation of TH1 (IL-2 and IFN-gamma) and TH2 (IL-4, IL-6) intragraft cytokine mRNAs compared with spontaneously accepting recipients, although IL-10 mRNA levels showed no differences between the two groups. The most striking difference was seen in IFN-gamma levels, which correlated well with the preferential deposition of IgG2a antibody isotype in the rejecting compared with the spontaneously accepting liver allograft recipients. These results suggested an association between liver allograft rejection and enhanced TH1 cytokine immune response. The ability to reject liver allografts by the adoptive transfer of splenocytes, but not serum, from a sensitized mouse ruled out preformed antibodies alone as a cause of rejection. However, spleen cytokine mRNA profiles showed no differences or trends in TH1 or TH2 expression in spontaneously accepting versus rejecting recipients, which suggested that the spleen is not a major site of alloreactive immune expansion. These data suggest that spontaneous acceptance of mouse liver allografts is associated with an insufficient intragraft TH1 cytokine response, the cause of which is currently under investigation.

Animals↗
PubMed1994

Suppression of lipopolysaccharide-induced macrophage nitric oxide and cytokine production in vitro by a novel lipopolysaccharide antagonist.

BACKGROUND: Many of the physiologic derangements resulting in septic shock are caused by inflammatory mediators such as nitric oxide (NO) and cytokines produced in response to bacterial endotoxin or, more specifically, lipopolysaccharide. The recent development of a novel class of lipopolysaccharide antagonists offers the opportunity to block this response selectively. In this article we investigated the ability of one of these antagonists, B464 (Eisai), to block lipopolysaccharide-induced release of macrophage NO and cytokines. METHODS: The mouse macrophage cell line RAW264.7 was grown in vitro and exposed to (1) media control, (2) B464 alone, (3) lipopolysaccharide alone, or (4) lipopolysaccharide plus graded concentrations of B464. Supernatants were assayed for nitrite plus nitrate, the stable end products of NO, as well as tumor necrosis factor-alpha and interleukin-6. Total cellular RNA was examined for inducible NO synthase and interleukin-6 mRNA. RESULTS: Lipopolysaccharide-stimulated increases in NO, tumor necrosis factor, and interleukin-6 production were blocked by B464. Reduction of NO was also seen at the level of inducible NO synthase mRNA. Induction of interleukin-6 mRNA was also suppressed. CONCLUSION: B464 is a novel potent specific antagonist of lipopolysaccharide-induced macrophage NO and cytokine production.

Amino Acid Oxidoreductases↗
PubMed1993

Evidence for early Th 2 T cell predominance in xenoreactivity.

Two distinct subsets of CD4+ Th lymphocytes have been characterized by their cytokine profiles: Th 1 (TH1) and Th 2 (TH2). While TH1 cells predominate in cell-mediated responses, TH2 cells support the humoral response. We have examined the mRNA cytokine profile of normal mouse lymphocytes in response to alloantigen versus xenoantigen (rat) in MLC, and present evidence to suggest that early in proliferative responses, alloreactivity is dominated primarily by TH1-type lymphocytes, while xenoreactivity is predominantly TH2. Normal mouse lymphocyte-responding cells were cultured in a one-way MLR with either allo or xeno antigen and examined for production of mRNA for cytokines characteristically produced by TH1 (IL-2, IFN-gamma) or TH2 (IL-4, IL-10) cells. Semiquantitative reverse transcription-polymerase chain reaction analysis was performed for mouse IL-2, IL-4, IL-10, and IFN-gamma mRNA. In the mouse anti-rat xeno response, mRNA for TH2 gene products were upregulated, with greater levels of IL-4 and IL-10 at 24 and 48 hr when compared with controls. In contrast, upregulation of mRNA for TH1 gene products occurred in the mouse anti-mouse allo response, with higher levels of IL-2 and IFN-gamma at 24 and 48 hr. In the anti-xeno response, upregulation of all 4 cytokines occurred by day 4 and peak levels of mRNA for all cytokines examined were 2-3 times that seen for the peak anti-allogeneic response. These data suggest that early xenorecognition may differ from allorecognition by differential activation of the TH2 subset. A better understanding of the balance between Th subset function and cytokine profile in allo and xeno reactivity may allow a more targeted and specific approach to control the early events in xenograft rejection.

Animals↗
PubMedDate not supplied

Graft cytokine mRNA activity in rat single lung transplants by reverse transcription-polymerase chain reaction: effect of cyclosporine.

Intragraft levels of cytokine mRNA were studied in an orthotopic rat left lung transplant model. Three groups of rats were compared at 7 days after transplantation. Isogeneic (Lewis to Lewis), allogeneic (Brown-Norway to Lewis) untreated, and cyclosporine-treated (25 mg/kg/day, intramuscularly) allogeneic animals underwent analysis of cytokine mRNA isolated from total RNA in freshly excised grafts. Reverse transcription-polymerase chain reaction amplification of interleukin (IL)-2, IL-4, and actin (control) mRNA was performed with custom-synthesized oligonucleotide amplimers targeted to known sequences of rat IL-2 and IL-4 cDNA. Semiquantitative analysis was performed by radioanalytic scanning of gel preparations. Sample specimens from the retrieved grafts were also graded histologically for rejection on a five-point scale. Rejection was most severe in the untreated allografts (p < 0.003). IL-2 mRNA was significantly greater in the untreated allografts when compared with isografts (p < 0.05) and cyclosporine-treated allografts (p < 0.05). No significant differences in IL-4 mRNA between groups were observed. We conclude that semiquantitative analysis of cytokine mRNA by reverse transcription-polymerase chain reaction is a useful and sensitive method for the study of acute rejection in lung grafts and that this technique may become an important tool in future studies of cytokine-mediated responses in cyclosporine-treated allografts.

Actins↗