Delayed rejection of fetal pig pancreas in CD4 cell deficient mice was correlated with residual helper activity

NK cells promote peritoneal xenograft rejection through an IFN-?-dependent mechanism

BACKGROUND

Natural killer (NK) cells have emerged as major players in anti-viral and anti-tumour immune responses. Like cytotoxic T lymphocytes (CTL), they express perforin and are potent secretors of gamma-interferon (IFN-gamma). However, there is conflicting evidence about their role in mediating rejection of xenogeneic tissue.

METHODS

A pig-to-mouse peritoneal cell model of xenotransplantation was used to investigate the effect of NK deficiency on xenograft recovery and the possible mechanisms behind this NK-mediated graft rejection. gamma c(-/-)RAG(-/-) mice were used as a model of NK deficiency. Additionally, NK cells were depleted in RAG(-/-) mice using anti-asialo GM1. The contributions of IFN-gamma, perforin and NKT cells were studied using knock-out mice that were depleted in vivo of T cells. Mice were injected with 10(7) pig cells intraperitoneally and peritoneal fluid was assessed 5 days later for xenograft recovery and phenotypic analysis. The requirement for NK cells for xenograft rejection was also assessed using luciferase-transfected porcine cells in a renal subcapsular model of transplantation.

RESULTS

Pig cell recovery was enhanced in both gamma c(-/-)RAG(-/-) and NK-depleted RAG(-/-) mice when compared with RAG(-/-) control mice. IFN-gamma(-/-) mice depleted of T cells also demonstrated superior graft survival compared with their B6 counterparts. However, there were minimal graft survival differences between Pfp(-/-) and B6 control mice. Similarly, a deficiency in NKT cells did not improve pig xenograft recovery from the peritoneum of these mice.

CONCLUSIONS

Therefore, we conclude that NK cells, but not NKT cells, are important mediators of xenograft rejection in the peritoneal cavity, and that their role may be unmasked in the absence of T cells. The mechanism for this xenorejection appears to involve IFN-gamma but is perforin independent.

Interleukin-6 modulates production of T lymphocyte-derived cytokines in antigen-induced arthritis and drives inflammation-induced osteoclastogenesis

OBJECTIVE

To determine the cellular mediators of antigen-induced arthritis (AIA) and the relative contribution of members of the interleukin-6 (IL-6) family and tumor necrosis factor (TNF) in AIA.

METHODS

AIA was induced in mice deficient in T and B lymphocytes, IL-6 (IL-6(-/-)), TNF (TNF(-/-)), IL-11 receptor, and oncostatin M receptor, by immunization with methylated bovine serum albumin (mBSA) followed 7 days later by intraarticular injection of mBSA. Arthritis severity was assessed histologically, and T lymphocyte responses were assessed in vitro. Anti-TNF neutralizing antibody was administered to wild-type mice during AIA. Bone marrow osteoclasts were generated in vitro via culture with RANKL and macrophage colony-stimulating factor.

RESULTS

AIA was dependent on CD4+ T lymphocytes, but not CD8+ T lymphocytes or B cells. IL-6(-/-) mice had reduced AIA severity and fewer osteoclasts at sites of bone erosion. This protective effect was not seen with a deficiency of other IL-6 family members and was similar to that in TNF(-/-) mice or wild-type mice receiving TNF blockade treatment. IL-6(-/-) CD4+ T lymphocytes from draining lymph nodes had reduced antigen-induced proliferation and produced less IL-17 and less RANKL, relative to osteoprotegerin, than cells from wild-type mice. Bone marrow from IL-6(-/-) mice generated fewer osteoclasts in vitro than bone marrow from either wild-type or TNF(-/-) mice.

CONCLUSION

AIA is driven by CD4+ T lymphocytes. IL-6 is an important mediator of bone destruction in AIA because it regulates T lymphocyte production of key osteoclastogenic cytokines and inflammation-induced bone marrow osteoclast differentiation. These findings have implications for reducing bone and joint damage in rheumatoid arthritis.

Stable skin-specific overexpression of human CTLA4-Ig in transgenic mice through seven generations

Skin graft rejection is a typical cellular immune response, mainly mediated by T cells. Cytotoxic T lymphocyte associated antigen 4-immunoglobin (CTLA4-Ig) extends graft survival by blocking the T cell co-stimulation pathway and inhibiting T cell activation. To investigate the efficacy of CTLA4-Ig in prolonging skin graft survival, human CTLA4-Ig (hCTLA4-Ig) was engineered to overexpress in mouse skin by transgenesis using the K14 promoter. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot assay indicated that the expression of CTLA4-Ig remained skin-specific and relatively constant compared to the internal control protein, AKT, through seven generations. The presence and concentration of the hCTLA4-Ig protein in transgenic mouse sera was determined by enzyme-linked immunosorbent assay (ELISA), and the results indicated that the serum CTLA4-Ig concentration also remained constant through generations. Survival of transgenic mouse skins grafted onto rat wounds was remarkably prolonged compared to that of wild-type skins from the same mouse strain, and remained comparable among all seven generations. This suggested that the bioactive hCTLA4-Ig protein was stably expressed in transgenical mice through at least seven generations, which was consistent with the stable skin-specific CTLA4-Ig expression. The results demonstrated that the transgenic expression of hCTLA4-Ig in skin driven by the K14 promoter remained constant through generations, and a transgenic line can be established to provide transgenic skin with extended survival reproducibly.

Establishment of Metanephros Transplantation in Mice Highlights Contributions by Both Nephrectomy and Pregnancy to Developmental Progression

BACKGROUND

It has been demonstrated that embryonic kidneys (metanephroi) xenotransplanted into the omentum of adult recipients continue to develop and display immune protection due to their more naïve immune presentation. To date, this has been achieved using rat, pig and human metanephroi, with unilateral nephrectomy (UNX) of recipient rats a requisite of renal development. The aim of this study was to adapt this approach for use in mice and examine the parameters affecting successful onward development in this species.

METHODS

Metanephroi at embryonic age (E) 13.5 were transplanted either onto the body wall, abdominal fat pads or omentum of recipient isogenic C57/Bl6 mice using either sutures or polyglycolic acid mesh. Having established greatest success with polyglycolic acid mesh on the body wall, E12.5 and 15.5 days metanephroi from C57/Bl6 mice were then transplanted onto the body wall of control (non-pregnant non-UNX), UNX or 12.5 days post-coitum pregnant isogenic recipients. After 7 days, implanted tissue was harvested and examined using histology and immunohistochemistry for markers of renal maturation. The mean number of S-shaped bodies and glomeruli per section were recorded and statistically analysed for significant differences between all recipient groups and untransplanted metanephroi. The degree of development was scored qualitatively.

RESULTS

Transplanted E12.5 metanephroi developed S-shaped bodies and glomeruli in all recipient groups, although there were statistically higher numbers of S-shaped bodies in UNX (n = 2) and pregnant recipients (n = 9) than in control recipients (n = 4). Continued development, as indicated by mature vascularized glomeruli, was only observed in those E15.5 metanephroi transplanted into pregnant recipients (n = 11) with a 15.5-fold increase in S-shaped bodies and 4-fold increase in glomeruli compared with control transplants (n = 12).

CONCLUSIONS

We have successfully established metanephros transplantation in mice and demonstrated enhancement of onward development of E12.5 metanephroi in response to both pregnancy and UNX. Using E15.5 metanephroi, continued development only occurred in pregnant recipients, implying pregnancy provides an environment conducive to continued organogenesis. This murine assay, when coupled with transgenically-tagged strains of mice, will allow the investigation of the relative contribution of donor and recipient cells to this process.

Effect of long-term culture on the expression of antigens and adhesion molecule in single porcine pancreatic endocrine cells

BACKGROUND

Changes in the expression of galactose (Gal) alpha1-3Gal, swine lymphocyte antigen (SLA) class II and intracellular adhesion molecule (ICAM)-1 of single porcine pancreatic endocrine (PE) cells during the culture period were investigated.

METHODS

Cultured porcine PE-cells were fixed in 10% buffered formalin for histological evaluation. At 1, 3, 6, 9 and 12 weeks of culture, mRNA was obtained from porcine PE-cells so that the expression of SLA class II and ICAM-1 genes could be examined by reverse transcriptase-polymerase chain reaction.

RESULTS

The rates of Galalpha1-3Gal and SLA class II-positive cells did not decrease during the culture period, but the rates of Galalpha1-3Gal and SLA class II strongly positive cells significantly decreased. ICAM-1-positive cells were scarcely observed during the culture period. SLA class II and ICAM-1 mRNAs were detected at 1 and 3 weeks of culture, but were not detected after 6 weeks of culture.

CONCLUSIONS

These results suggest that partial reduction in the expression of these antigens could be obtained by a long-term culture.

Responses against complex antigens in various models of CD4 T-cell deficiency: surprises from an anti-CD4 antibody transgenic mouse

The most common models of CD4 T-cell deficiency are mice exogenously injected with anti-CD4 antibody (Ab), CD4 knockout (CD4-/-) and major histocompatibility complex (MHC) class II knockout (class II-/-) mice. We recently described the anti-CD4 Ab transgenic mouse (GK) as an improved CD4 cell-deficient model. This review compares this new GK mouse model with the widely available class II-/- and CD4-/- mice, when exposed to complex antigens (foreign grafts and during bacterial or viral infection). We highlight here the cytometric and functional differences (including Ab isotype, viral or bacterial clearance, and graft survival) among these CD4 cell-deficient models. For example, whereas grafts are generally rejected in class II-/- and CD4-/- mice as quickly as in wild-type mice, they survive longer in GK mice. Also, CD4-/- mice produce IgG against both simple model and complex antigens, but class II-/- and GK mice produce small amounts of IgG2a against complex antigens but not simple model antigens. These differences harbinger the caveats in the use of these various mice.

IFN-gamma but not IL-4 is important for mouse CD4+ T cell-mediated macrophage activation following their exposure to pig cells in vitro

In order to investigate the mechanism by which CD4+ T cells and macrophages interact in the xenogeneic immune response, murine CD4+ T cells and macrophages were used as responder cells in culture with irradiated fetal pig spleen cells (FPSC) as pig xenogeneic stimulators. In this in vitro model, murine CD4+ T cells and macrophages were cultured individually, or together with FPSC. In addition, mouse CD4+ T cells were also cultured with autologous macrophages which were previously stimulated by FPSC. The cultured murine cells were analyzed for expression of CD4+ T cell and macrophage activation markers (cell surface markers and cytokines) as well as cytokine production. CD4+ T cells and macrophages cultured alone or together without FPSC showed unchanged low levels of expression of activation markers. Coculture of macrophages with FPSC and in the absence of CD4+ T cells induced increased expression levels of all the activation markers examined except B7.2 and ICAM-1. Addition of CD4+ T cells to the coculture further enhanced this up-regulation. Coculture of CD4+ T cells with FPSC-stimulated macrophages, but not naive macrophages, or FPSC alone, resulted in significantly increased numbers of CD4+ T cells coexpressing their activation markers, especially IFN-gamma and CD40L, and this expression was enhanced further by including FPSC in the coculture. The activation of both CD4+ T cells and macrophages in their coculture with FPSC was suppressed by neutralizing IFN-gamma but not IL-4. Our results demonstrated that interaction of CD4+ T cells and autologous macrophages was required for their optimal activation in response to pig xenogeneic stimulation. The mechanisms involved included cell-cell and/or cytokine interactions, and in particular IFN-gamma mediated communication was involved. Macrophages activated by pig cells in the absence of CD4+ T cells were able to activate naive CD4+ T cells, thus providing an important communication pathway between innate immune activation and a T cell mediated response in xenograft rejection.

Without CD4 help, CD8 rejection of pig xenografts requires CD28 costimulation but not perforin killing

Although CD4 cells are major mediators in cellular rejection of fetal pig pancreas (FPP) in the mouse, rejection still occurs in the absence of CD4 cells, albeit with delayed kinetics. CD4 cell-independent mechanisms of cellular rejection are poorly understood. To investigate the involvement of CD8 T cells in FPP rejection and their activation requirements, we used mice transgenic for anti-CD4 Ab; this is the most complete model of CD4 cell deficiency. We showed that in such mice FPP was infiltrated with CD8 cells starting from 2 wk posttransplantation and FPP was eventually rejected 8 wk posttransplantation. Ab depletion of CD8 cells greatly improved the survival of FPP and reduced cell infiltration at the graft site. This suggests that CD8 cells can mediate the rejection of porcine xenografts in the absence of CD4 cells. This CD8-mediated rejection of FPP is independent of their perforin-mediated lytic function, as graft survival was not affected in mice deficient in perforin. The production of IFN-gamma and IL-5 by the graft infiltrates indicates that CD8 cells may act through cytokine-mediated mechanisms. Remarkably, in the absence of CD4 cells, lymphocyte infiltration at the graft site was absent in mice transgenic for CTLA4Ig such that the islet grafts flourished beyond 24 wk. In contrast, rejection was little affected by CD40 ligand deficiency. Therefore, we show that CD8 cells are activated to mediate FPP rejection independent of perforin and that this CD4-independent activation of CD8 cells critically depends on B7/CD28 costimulation.