Temporal sequence of transcription of perforin, Fas ligand, and tumor necrosis factor-alpha genes in rejecting skin allografts

Cytotoxic effector function of CD4-independent, CD8(+) T cells is mediated by TNF-α/TNFR

BACKGROUND

Liver parenchymal cell allografts initiate both CD4-dependent and CD4-independent, CD8(+) T cell-mediated acute rejection pathways. The magnitude of allospecific CD8(+) T cell in vivo cytotoxic effector function is maximal when primed in the presence of CD4(+) T cells. The current studies were conducted to determine if and how CD4(+) T cells might influence cytotoxic effector mechanisms.

METHODS

Mice were transplanted with allogeneic hepatocytes. In vivo cytotoxicity assays and various gene-deficient recipient mice and target cells were used to determine the development of Fas-, TNF-α-, and perforin-dependent cytotoxic effector mechanisms after transplantation.

RESULTS

CD8(+) T cells maturing in CD4-sufficient hepatocyte recipients develop multiple (Fas-, TNF-α-, and perforin-mediated) cytotoxic mechanisms. However, CD8(+) T cells, maturing in the absence of CD4(+) T cells, mediate cytotoxicity and transplant rejection that is exclusively TNF-α/TNFR-dependent. To determine the kinetics of CD4-mediated help, CD4(+) T cells were adoptively transferred into CD4-deficient mice at various times posttransplant. The maximal influence of CD4(+) T cells on the magnitude of CD8-mediated in vivo allocytotoxicityf occurs within 48 hours.

CONCLUSION

The implication of these studies is that interference of CD4(+) T cell function by disease or immunotherapy will have downstream consequences on both the magnitude of allocytotoxicity as well as the cytotoxic effector mechanisms used by allospecific CD8(+) cytolytic T cells.

Rapid, large-scale formation of porcine hepatocyte spheroids in a novel spheroid reservoir bioartificial liver

We have developed a novel bioreactor based on the observation that isolated porcine hepatocytes rapidly and spontaneously aggregate into spheroids under oscillation conditions. The purpose of this study was to characterize the influence of oscillation frequency (0.125 Hz, 0.25 Hz), cell density (1-10 x 10(6) cells/mL), and storage condition (fresh, cryopreserved) of porcine hepatocytes on the kinetics of spheroid formation. The viability and metabolic performance of spheroid hepatocytes was also compared to monolayer culture. We observed that both fresh and cryopreserved porcine hepatocytes began formation of spheroids spontaneously at the onset of oscillation culture. Spheroid size was directly related to cell density and time in culture, though inversely related to oscillatory frequency. Spheroid formation by fresh porcine hepatocytes was associated with decreased cell death (lactate dehydrogenase release, 1.3 +/- 1.0 vs. 3.1 +/- 0.7 U/mL, P < 0.05) and increased metabolic performance (albumin production, 14.7 +/- 3.3 vs. 4.6 +/- 1.4 fg/c/h, P < 0.0001; ureagenesis from ammonia, 267 +/- 63 vs. 92 +/- 13 micromol/L/h, P < 0.001) compared with monolayer culture. In conclusion, based on the favorable properties of rapid spheroid formation, increased hepatocellular function, and ease of scale-up, the spheroid reservoir bioreactor warrants further investigation as a bioartificial liver for support of liver failure.

Role of CD4+ and CD8+ T cells in murine skin and heart allograft rejection across different antigenic desparities

The factors that influence the relative contribution of the T cell subsets to allograft rejection remain unclear. We compared skin and heart rejection in CD4 Knockout (KO), and CD8 KO mice across full-, minor-, and class II histocompatibility antigen (HA) mismatches. Skin allografts were rejected by either CD4+ or CD8+ T cells alone at any degree of antigenic mismatch. However, either the absence of CD4+ cells or a lesser degree of HA mismatch resulted in prolongation of graft survival. In contrast, fully allogeneic heart grafts were accepted in CD4 KO recipients, and minor HA mismatched heart grafts were accepted by both CD4 KO and CD8 KO mice. Thus, the T cell subsets required for allograft rejection are determined by the immunogenicity of the tissue transplanted. In the absence of CD8+ T cells, perforin and Fas ligand (FasL) but not granzyme B mRNA were detected in rejecting grafts. Thus, granzyme B is a CD8+ cytotoxic T lymphocyte (CTL)-specific effector molecule.

Culture confluence regulates gene expression of normal human keratinocytes

Keratinocytes are frequently used to examine efficacy of wound healing products and dermatological agents in vitro. Cultured keratinocyte sheets are also used as autologous or allogenic grafts to promote wound closure. Because it is well known that the expression patterns of keratin genes change when cell cultures reach confluence, we investigated the expression pattern of wound healing-related genes, including growth factors and cytokines. Of additional particular interest is a novel wound healing related factor, secretory leukocyte protease inhibitor (SLPI), which appears to enhance tissue repair. We found that the expression pattern varied for specific genes expressed by keratinocytes as confluence was reached. Specifically, SLPI expression peaked in the early postconfluent state and vascular endothelial growth factor and amphiregulin in the late postconfluent state. Some gene products exhibit autocrine activity, whereas others exert paracrine regulation of growth. These findings indicate that it is critical to define the growth and differentiation state of human keratinocyte cultures to better determine responses and efficacy in vitro to various dermatological/wound care agents tested.

Unimpaired Allorejection of Cells Deficient for the Mannose 6-Phosphate Receptors Mpr300 and Mpr46

Cytotoxic T lymphocytes (CTL) play an important role in the rejection of allogeneic cells and organs. CTL secrete granzymes and perforin as cytotoxic effector molecules. The mannose 6-phosphate receptor (Mpr)300 has been reported to function as receptor for granzyme B on target cells and to be essential for the rejection of allogeneic cells in vivo. Using mouse embryonal fibroblasts from Mpr300 and Mpr46 knockout mice, we show that both Mpr 300 and Mpr46 are dispensable on target cells for lysis and apoptosis mediated by alloreactive CTL in vitro and for allorejection in vivo. In agreement with a postulated function of Mpr300 as a tumor suppressor gene, deficiency of Mpr300 appears to promote cellular proliferation and tumorigenicity but not resistance to allorejection.

Does HLA-Dependent Chimerism Underlie the Pathogenesis of Juvenile Dermatomyositis?

Juvenile dermatomyositis (JDM) is a multisystem autoimmune disease that at times resembles chronic graft-vs-host disease. This led us to suggest that nonself cells may play a role in the disease process. In this study we examined the relationship between HLA genotype and the presence of maternally derived chimeric cells in JDM patients and healthy controls, and assessed immunologic activity in the chimeric cells. We identified chimeric cells more often in children with JDM (60 of 72) than in their unaffected siblings (11 of 48) or in healthy controls (5 of 29). The presence of chimerism in the JDM patients, their healthy siblings, and unaffected control children was associated with a HLA-DQA1*0501 allele in the mother (p = 0.011). Further, we show that maternally transferred chimeric T cells are responsive to the host's (JDM childs') lymphocytes (33.75 +/- 8.4 IFN-gamma-producing cells from JDM cells vs 5.0 +/- 1.25 from maternal cells), and that this is a memory response. These combined data indicate that chimeric cells play a direct role in the JDM disease process and that the mother's HLA genotype facilitates the transfer and/or persistence of maternal cells in the fetal circulation.

Mitosis increases levels of secretory leukocyte protease inhibitor in keratinocytes

Chronic wounds are a major health care burden. Multiple factors produced by healing wounds play important roles in efficient and orderly wound healing. Secretory leukocyte protease inhibitor (SLPI) is constitutively expressed in epithelial cells, and its expression is increased by inflammation. SLPI has antimicrobial activities and improves wound healing. We hypothesized that SLPI expression correlates with keratinocyte growth rate and is increased by epidermal growth factor (EGF). Keratinocytes were isolated from neonatal foreskin. Subconfluent and confluent culture conditions were used. SLPI-specific primers were designed for use in quantitative-competitive reverse-transcription polymerase chain reaction assays to detect and quantify SLPI mRNA expression levels. SLPI levels were increased 2-fold in subconfluent cultures and 1.6-fold in confluent cultures to which EGF had been added. Confluent cultures also demonstrated 7-fold (growth factor depleted) and 6-fold (EGF) increase in SLPI RNA copy number, compared to subconfluent cultures. The results indicate that EGF increases SLPI expression.

Early chemokine cascades in murine cardiac grafts regulate T cell recruitment and progression of acute allograft rejection

The identification of early inflammatory events after transplant in solid tissue organ grafts that may direct T cell recruitment and promote acute allograft rejection remain largely unknown. To better understand temporal aspects of early inflammatory events in vascularized organ grafts, we tested the intragraft expression of four different chemokines in heterotopically transplanted A/J (H-2(a)) and syngeneic heart grafts in C57BL/6 (H-2(b)) recipient mice from 1.5 to 48 h after transplant. Similar temporal expression patterns and equivalent levels of chemokine expression were observed in both syngeneic and allogeneic cardiac allografts during this time period. Expression of the neutrophil chemoattractant growth-related oncogene alpha (KC) was observed first and reached peak levels by 6 h after transplant and was followed by the monocyte/macrophage chemoattractant protein-1 (JE) and then macrophage inflammatory proteins 1beta and 1alpha. Administration of rabbit KC antiserum to allograft recipients within 30 min of cardiac transplantation attenuated downstream events including intra-allograft expression of the T cell chemoattractants IFN-gamma-inducible protein-10 and monokine induced by IFN-gamma, cellular infiltration into the allograft, and graft rejection. Similarly, depletion of recipient neutrophils at the time of transplantation significantly extended allograft survival from day 8 to 10 in control-treated recipients up to day 21 after transplant. These results indicate the induction of highly organized cascades of neutrophil and macrophage chemoattractants in cardiac grafts and support the proposal that early inflammatory events are required for optimal recruitment of T cells into allografts during the progression of acute rejection of cardiac allografts.

Swift development of protective effector functions in naive CD8(+) T cells against malaria liver stages

We generated T cell receptor transgenic mice specific for the liver stages of the rodent malaria parasite Plasmodium yoelii and studied the early events in the development of in vivo effector functions in antigen-specific CD8(+) T cells. Differently to activated/memory cells, naive CD8(+) T cells are not capable of exerting antiparasitic activity unless previously primed by parasite immunization. While naive cells need to differentiate before achieving effector status, the time required for this process is very short. Indeed, interferon (IFN)-gamma and perforin mRNA are detectable 24 h after immunization and IFN-gamma secretion and cytotoxic activity are detected ex vivo 24 and 48 h after immunization, respectively. In contrast, the proliferation of CD8(+) T cells begins after 24 h and an increase in the total number of antigen-specific cells is detected only after 48 h. Remarkably, a strong CD8(+) T cell-mediated inhibition of parasite development is observed in mice challenged with viable parasites only 24 h after immunization with attenuated parasites. These results indicate that differentiation of naive CD8(+) T cells does not begin only after extensive cell division, rather this process precedes or occurs simultaneously with proliferation.

A serine protease inhibitor, N-alpha-tosyl-l-lysine chloromethyl ketone, prolongs rat hepatic allograft survival

BACKGROUND

Serine protease inhibitors have profound suppressive effects on cellular and humoral immune responses. We investigated the effect of a serine protease inhibitor, N-alpha-tosyl-l-lysine chloromethyl ketone (TLCK), on hepatic allograft survival in rats. Methods. Orthotopic hepatic transplantation was performed in an ACI (RT1(a))-to-LEW (RT1(1)) rat combination. TLCK was administered continuously at a dose of 4.4 mg/kg/day using an osmotic subcutaneous infusion minipump.

RESULTS

TLCK prolonged hepatic allograft survival. Histologic staging of acute rejection based on Banff criteria in TLCK-treated hepatic allografts was significantly lower than in untreated allografts. TLCK significantly reduced serum concentrations of interferon (IFN)-gamma and tumor necrosis factor (TNF) alpha in allograft recipients. TNF-alpha mRNA levels in TLCK-treated allografts were significantly lower than in untreated allografts. TLCK also decreased perforin mRNA levels in hepatic allografts. Hepatic infiltrates eluted from TLCK-treated allografts showed significantly lower cell-mediated lympholytic activity against donor Con A blast cervical lymph node cells than those from untreated allografts. In vitro, TLCK suppressed interleukin-2 production and [(3)H]thymidine incorporation into an allogeneic mixed lymphocyte reaction.

CONCLUSION

TLCK suppressed acute allograft rejection, suggesting a novel immunosuppressive strategy for therapy of acute organ rejection.

Phenotypic and functional characterization of mouse hepatic CD8 alpha+ lymphoid-related dendritic cells

Recently, attention has focussed on phenotypic and functional differences between classic myeloid dendritic cells (DC), and DC that reportedly develop from an early, committed lymphoid precursor. In mice, DC from these separate hemopoietic lineages differ by their surface expression of CD8 alpha. We undertook a comparative study of CD8 alpha+ (CD11blow; lymphoid-related) and CD8 alpha- (CD11bhigh; myeloid) DC isolated from mouse liver. CD8 alpha+ and CD8 alpha- DC each constituted </=1.0% of the freshly isolated, normal nonparenchymal cells (NPC). Both populations were enriched 10-15% by overnight culture and metrizamide density centrifugation. Flt3 ligand (Flt3L) potently induced equal expansion of both subsets in vivo. Tissue-resident CD8 alpha+ DC, freshly isolated from Flt3L-treated mice, existed primarily as immature cells (CD11c+, CD11blow, CD40-/low, CD80low, CD86low, MHC class IIlow), consistent with previous observations regarding bulk DC freshly isolated from nonlymphoid tissues. Following overnight culture in GM-CSF, CD8 alpha+ DC underwent phenotypic and functional maturation equivalent to that observed for CD8 alpha- DC. CD95 ligand (FasL) mRNA was detected in both immature and mature DC of each subset. In vitro analysis confirmed that flow-sorted, mature CD8 alpha+ and CD8 alpha- DC were strong and equally efficient stimulators of allogeneic T cell proliferation in primary MLR. Both immunohistochemical and genomic DNA analysis revealed that in vivo, sorted CD8 alpha+ DC trafficked from s.c. sites to T cell areas of allogeneic lymphoid tissue and were equally efficient at priming naive T cells compared with CD8 alpha- DC. This is the first comparative study of lymphoid-related DC isolated from nonlymphoid tissue.

Intraallograft chemokine RNA and protein during rejection of MHC-matched/multiple minor histocompatibility-disparate skin grafts

Chemokines direct leukocyte recruitment into sites of tissue inflammation and may facilitate recruitment of leukocytes into allografts following transplantation. Although the expression of chemokines during rejection of MHC-disparate allografts has been examined, chemokine expression in MHC-matched/multiple minor histocompatibility Ag-disparate allografts has not been tested. The intraallograft RNA expression of several C-X-C and C-C chemokines was tested during rejection of full thickness skin grafts from B10. D2 donors on control Ig-, anti-CD4 mAb-, and anti-CD8 mAb-treated BALB/c recipients. In all recipients, two patterns of intragraft chemokine expression were observed during rejection of these grafts: 1) macrophage-inflammatory protein-1alpha, macrophage-inflammatory protein-1beta, GRO-alpha (KC), JE, and IFN-gamma-inducible protein (IP-10) were expressed at equivalent levels in allo- and isografts for 2-4 days posttransplant and then returned to low or undetectable levels; and 2) IP-10 and monokine induced by IFN-gamma (Mig) were expressed in the allografts 3 days before rejection was completed, suggesting a possible role in recruiting primed T cells into the allograft. Three days before completion of rejection, intraallograft IP-10 protein was restricted to the epidermis, whereas Mig was located in the lower dermis and associated with the intense infiltration of mononuclear cells. Treatment of B10.D2 recipients with rabbit antiserum to Mig, but not to IP-10, delayed rejection of the allografts 3-4 days. The results suggest that Mig mediates optimal recruitment of T cells into MHC-matched/multiple minor histocompatibility Ag-disparate allografts during rejection.

Quantification of cytotoxic T-cell gene transcripts in human lung transplantation

BACKGROUND

Differentiating between acute rejection and cytomegalovirus (CMV) infection is one of the major challenges of lung transplantation. The aims of this study were to: (1) quantify the transcription of the cytotoxic T lymphocyte (CTL) effector molecules in the bronchoalveolar lavage (BAL) of lung transplant recipients and (2) evaluate the clinical usefulness of this technique.

METHODS

Sixty-six single-lung, double-lung, or heart-lung transplant patients were prospectively enrolled in the study. BAL was performed either for routine surveillance or for acute graft dysfunction. RNA was extracted from BAL cell pellets and underwent competitive reverse transcription-assisted polymerase chain reaction (RT-PCR) for perforin, granzyme B, granulysin, and Fas ligand. Gene transcript analysis was compared to clinical diagnosis established by conventional methods [BAL microbiological and transbronchial biopsy (TBB) analyses].

RESULTS

After exclusion of several BAL according to the study criteria, 62 BAL were submitted for data analysis. Significantly higher expression of all the analyzed transcripts was found during CMV infection, compared with each of the other defined diagnostic categories, namely nonsignificant pathology, acute rejection, and nonviral pulmonary infection.

CONCLUSION

Quantification by competitive RT-PCR of the CTL effector molecule transcripts (perforin, granzyme B, granulysin, and Fas ligand) could represent a valuable tool for the differential diagnosis of graft dysfunction in lung transplantation.