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In vascularized composite allotransplantation (VCA), invasive tissue biopsies remain the gold standard in diagnosing rejection carrying significant morbidity. We aimed to show feasibility of tape-stripping for noninvasive immune monitoring in VCA. Tape-stripping was performed on allografts and native skin of upper extremity transplant recipients. Healthy nontransplanted individuals served as controls. The technique was also used in swine on naive skin in nontransplanted animals, native skin of treated, transplanted swine, nonrejecting VCAs, and rejecting VCAs. Extracted protein was analyzed for differences in cytokine expression using Luminex technology. Significantly decreased levels of INFγ and IL-1Ra were seen between human allograft samples and native skin. In swine, rejecting grafts had increased IL-1Ra compared to naive and native skin, decreased levels of GM-CSF compared to native skin, and decreased IL-10 compared to nonrejecting grafts. Unsupervised hierarchical clustering revealed rejecting grafts separated from the nonrejecting (P = 0.021). Variable importance in projection scores identified GM-CSF, IL-1Ra, and IL-2 as the most important profiles for group discrimination. Differences in cytokine expression are detectable in human VCA patient native skin and VCA graft skin using a noninvasive tape-stripping method. Swine studies suggest that differences in cytokines between rejecting and nonrejecting grafts are discernable.

The immune system undergoes rapid reconstitution after autologous or syngeneic bone marrow transplantation with the re-establishment of tolerance to self-antigens. Administration of drugs such as cyclosporine that inhibit thymic-dependent clonal deletion disrupts the reconstitution of the immune system. In the absence of a peripheral regulatory T cells eliminated by the preparative regimen, systemic autoimmunity with pathology similar to graft-versus-host disease often develops. Moreover, the resolution of autoaggression is dependent on the reconstitution of CD4+ regulatory T cells. This study examined the specificity and function of this regulatory population assessed ex vivo that plays a critical role in down-regulating the autoreactive T lymphocyte response in cyclosporine-induced syngeneic graft-versus-host disease. The results suggest that both the antigen-specific regulatory and pathogenic effector T cells recognize a common peptide antigen framework (CLIP, a peptide derived from the invariant chain) presented by major histocompatibility complex class II molecules. Analysis of the CD4+ T-cell compartment revealed two subsets of CLIP-reactive T cells that differentially require the N- and C-terminal flanking domain of this peptide. Regulatory function is associated with the cells that require the C-terminal flanking domain. This population expresses the Foxp3 nuclear transcription factor and plays a critical role in re-establishing tolerance to self-major histocompatibility complex class II antigens. In addition to suppressing the production of type 1 cytokines, these regulatory Tcells can direct the apoptotic death of the pathogenic autoreactive lymphocytes. This study also suggests that the development of functional regulatory activity is an active response initiated by the presence of autoreactive lymphocytes that can present the target antigen (major histocompatibility complex class II CLIP) to the regulatory T cells. Moreover, this process can be mimicked by peptide antigen in the absence of the pathogenic effector lymphocytes leading to the development of functional regulatory T-cell activity.

Several clinical trials evaluating the induction of autoimmune graft-versus-host disease (GVHD) after autologous bone marrow transplantation (BMT) as antitumor immunotherapy have shown that autologous GVHD is associated with increased production of interleukin (IL)-10. The induction of autologous GVHD also segregated with single nucleotide polymorphisms in the IL-10 promoter region (IL-10 -592 and IL-10 -1082 ) and with CA repeats in the first intron of the interferon (IFN)-gamma gene. Polymorphisms within these promoter regions can significantly modify the cytokine response because of differential transcription factor efficiency. This study evaluated the relationship between inheritance of polymorphisms within the IL-10 promoter and in the IFN-gamma gene and the overall survival of patients who received autologous BMT for metastatic breast cancer. Peripheral mononuclear cells from 87 women enrolled in 3 autologous BMT (plus induction of autologous GVHD) clinical trials were examined. By using a Cox proportional hazard model, trends in survival after autologous BMT were analyzed. The model included inheritance polymorphisms of IL-10 -592 , IL-10 -1082 , CA repeats within the first intron of the IFN-gamma gene, estrogen and progesterone receptor status, and stage of disease. Increased survival was significantly associated with patients having the IL-10 -592 promoter allele associated with high IL-10 production (hazard ratio, 0.23; 95% confidence interval, 0.09-0.55; P = .001). The effect of the strong IL-10 promoter allele on survival seems to be independent of the development of clinical autologous GVHD. However, decreased survival was significantly associated with patients having CA repeats associated with higher IFN-gamma transcription (hazard ratio, 2.34; 95% confidence interval, 1.21-4.54; P = .011). Inheritance of specific alleles that modify IL-10 and IFN-gamma production may have unexpected effects on the efficacy of immune-based strategies after autologous BMT. Additional studies are necessary to further define the influence of IL-10 and IFN-gamma on the immune response after BMT.

Administration of cyclosporine (CyA) following autologous bone marrow transplantation elicits a T-lymphocyte autoaggression syndrome with remarkable similarity to acute and chronic graft-versus-host disease (GVHD). This syndrome termed syngeneic (S) GVHD is mediated by a restricted repertoire of autoreactive T cells that promiscuously recognize major histocompatibility complex (MHC) class II determinants in association with a peptide from the invariant chain (CLIP). The present studies evaluated and compared antigen-specific autoreactive T cells during acute and chronic SGVHD isolated ex vivo with a soluble MHC class II-immunoglobulin (sMHC class II-Ig) molecular construct. Two major subsets were detected that had overlapping specificity recognizing the MHC class II binding domain of CLIP but were differentially dependent on the N- and C-terminal flanking domains of this peptide. Both subsets were detected in acute and chronic SGVHD. Interestingly, the cytokine profiles of the CLIP-reactive T cells closely correlated with the onset and progression of disease. Levels of type 1 cytokines, particularly IFN-γ mRNA production assessed by quantitative polymerase chain reaction (PCR), were dominant during acute SGVHD, whereas chronic SGVHD was associated with type 2 cytokine mRNA production. Although there was a dramatic polarization with respect to cytokine production, only subtle changes in antigen specificity were detected. Of additional interest, autoreactive T cells producing IL-10 mRNA were detected in both acute and chronic SGVHD, suggesting that this cytokine may play an important but perhaps paradoxical role in both the onset and progression of this experimental autoaggression syndrome.

Graft-versus-host disease (GVHD) is characterized by an impairment of mechanisms that underlie the development of immunologic tolerance. Although the cytokine storm associated with GVHD leads to expression of cell surface markers on both effector and regulatory T cells, regulatory CD4+ T cells that play an instrumental role in the maintenance of tolerance appear to uniquely express the Foxp3 transcriptional repressor. Foxp3 mRNA expression was significantly decreased in peripheral blood mononuclear cells from patients with either allogeneic GVHD or autologous GVHD compared with patients without GVHD. Expression of Foxp3 negatively correlated with the severity of GVHD but positively correlated with recent thymic emigrants. The results suggest that defective thymic function contributes to the impaired reconstitution of immune regulatory mechanisms following transplantation. The decrease in regulatory mechanisms after transplantation appears to provide an environment permissive to the development of GVHD. (Blood. 2004;104:2187-2193)

BACKGROUND Administration of cyclosporine after syngeneic bone marrow transplantation elicits a systemic autoaggression syndrome termed syngeneic graft-versus-host disease (SGVHD). The effector T cells recognize a peptide from the invariant chain termed CLIP (MHC class II invariant chain peptide) presented on MHC class II molecules. Moreover, the N-terminal flanking region of CLIP interacts with the T-cell receptor (TcR) beta chain. METHODS The current study uses a novel approach to isolate and examine the responding T cells ex vivo. A soluble MHC class II molecule using immunoglobulin (Ig)G (MHC class II-Ig) as a scaffold was constructed. The MHC class II-Ig molecule loaded with different peptide variants of CLIP (lacking the N-terminal or C-terminal flanking regions of CLIP) was used to isolate antigen-specific T cells from animals with SGVHD by panning or by flow cytometric sorting. RESULTS Two subsets of antigen specific T cells restricted by the N- and C-terminal flanking regions of CLIP can be isolated during acute SGVHD that express the Vbeta8.5 TcR determinant but secrete different cytokines (interferon [IFN]-gamma, interleukin [IL]-10) as detected by real-time quantitative polymerase chain reaction (PCR). Spectratyping of the complementarity-determining region 3 regions reveals that the N-terminal CLIP reactive population has greater diversity in both the CDR3 and J regions than the C-terminal CLIP reactive subset. Interestingly, the N-terminal CLIP reactive cells can be preferentially detected in the target tissues during acute SGVHD. However, only IFN-gamma messenger (m)RNA was detected in the tissues. CONCLUSION The ability to isolate and examine antigen specific T cells ex vivo has revealed unexpected differences in TcR diversity and cytokine production in SGVHD.

Administration of cyclosporine A (CsA) after autologous stem cell transplantation elicits an autoimmune syndrome with pathology similar to graft-versus-host disease (GVHD). This syndrome, termed autologous GVHD, is associated with the appearance of autoreactive T cells directed at major histocompatibility class (MHC) class II antigens. In the rat model of autologous GVHD, clonal analysis reveals that the effector T cells are highly conserved and recognize a peptide from the invariant chain peptide presented by MHC class II. Although human autologous GVHD effector T cells share a similar phenotypic specificity, clonality of the response in humans has not been determined. To examine the human effector T-cell response, the T-cell repertoire of peripheral blood lymphocytes was assessed by complementarity-determining region 3 (CDR3) size distribution analysis and T-cell clonotype analysis in 26 patients treated with CsA after transplantation. Autologous GVHD developed in 3 of 4 patients with human leukocyte antigen (HLA)-DRB1*0701, and clonal expansions of β-chain variable region (BV)16+ T cells were shared. Clonal expansions within BV15+ and BV22+ T cells were also detected in 4 of 6 patients with HLA-DRB1*1501 and in 3 of 4 patients with HLA-DRB1*0401, respectively. Sequencing of BV16 cDNA for which the CDR3 size pattern exhibited apparent clone predominance revealed an identical CDR3 peptide sequence in 2 different patients, one with HLA-DRB1*0701 and the other with HLA-DRB1*1502. These findings indicate that the discrete antigen-driven expansion of T cells is involved in autologous GVHD.

Administration of the immunosuppressive drug cyclosporine after syngeneic or autologous bone marrow transplanta- tion elicits a T-lymphocyte-dependent autoimmune syndrome similar to graft-versus-host disease (GVHD). The onset of this autoaggression syndrome, termed syngeneic GVHD, is associated with the development of a highly restricted re p e rt o i re of CD8 + a u t o reactive T cells that recognize a peptide from the invariant chain, termed CLIP, p resented by major histocompatibility complex (MHC) class II molecules. Clonal analysis reveals 2 distinct subsets of a u t o reactive T cells defined by their activation re q u i rement for either the N-terminal or the C-terminal fla n k i n g regions of CLIP and by their cytokine pro file. The studies here reveal that the autoreactive T-cell clones re q u i r i n g the N-terminal flanking region of CLIP produce type 1 cytokines (interf e ron (IFN)-γ , interleukin (IL)-2, and tumor n e c rosis factor-α). In contrast, the autoreactive T-cell clones that re q u i re the C-terminal flanking region of CLIP p roduce type 2 cytokines (IL-4, IL-10, transforming growth factor-β). As assessed in a local graft-versus-host re a c- tion assay, the N-terminal fla n k i n g - restricted clones mediate changes consistent with acute GVHD, whereas the clones responsive to the C-terminal flanking region do not. More o v e r, the autoreactive T-cell clones restricted by the C - t e rminal flanking region of CLIP ameliorate the pathogenic potential of the cells responsive to the N-term i n a l flanking region of CLIP. The mechanism accounting for this re g u l a t o ry affect appears to be the downregulation of mRNA message for type 1 cytokines (IFN-γ and IL-2). The C-term i n a l - restricted autoreactive T-cell clones, how- e v e r, could manifest disease with dermal changes similar to those seen in chronic syngeneic GVHD, provided that I F N -γ was present. Consistent with these observations was the demonstration that type 1 cytokines are pre f e re n t i a l l y detected during the acute phase of syngeneic GVHD, whereas type 2 cytokines dominate during the chronic phase. The results suggest that acute and chronic syngeneic GVHD is mediated by distinct autoreactive T cells, which are separated by their fine specificity for the CLIP-MHC class II complex and by their cytokine pro fil e s .

Background. Administration of the immunosuppressive drug cyclosporine after syngeneic/autologous bone marrow transplantation paradoxically elicits a systemic autoimmune syndrome resembling graft-versus-host disease (GVHD). This syndrome, termed autologous or syngeneic GVHD, is associated with the development of a highly restricted repertoire of cytolytic T lymphocytes that promiscuously recognizes major histocompatibility complex class II determinants, including self. Methods. Vβ8.5+CD8+ effector lymphocytes and T-cell clones were isolated from Lewis rats with cylosporine-induced syngeneic GVHD. The specificity of the effector T cells and T-cell clones was examined in vitro. The pathogenicity of the T-cell clones was confirmed in vivo using a local graft-versus-host reaction assay. Results. Clonal analysis reveals that the pathogenic effector T cells recognize a peptide from the invariant chain termed CLIP in association with major histocompatibility complex class II determinants. Moreover, there appears to be an additional interaction between the N-terminal flanking region of CLIP and the Vβ segment of the T cell receptor. Conclusion. The results suggest that recognition of this highly conserved peptide along with the additional interaction between the flanking region and the T cell receptor may account for the promiscuous activity of the autologous/syngeneic GVHD autoreactive T cells.

OX40 (CD134), a member of the tumor necrosis factor receptor superfamily, is expressed on activated T cells, including CD4 + CD25 + T regulatory (Treg) cells. To investigate the kinetics of OX40–OX40L in graft-versus-host disease (GVHD), OX40 mRNA transcript levels were temporally examined in peripheral blood mononuclear cells (PBMCs) from patients undergoing either allogeneic (allo) bone marrow transplantation (alloBMT) or autologous (auto) BMT with the induction of autoGVHD by cyclosporine (CsA) treatment posttransplant. Real-time quantitative PCR analysis revealed that OX40 mRNA expression decreased significantly in PBMCs from patients with either alloGVHD or autoGVHD compared with healthy individuals. No differences were detected between patients developing alloGVHD and those who did not develop this posttransplant complication. On the other hand, a decrease in OX40 mRNA levels correlated directly with the development of autoGVHD. Moreover, the upregulation of OX40 gene expression coincided with the resolution of autoGVHD. Interestingly, expression of OX40 by CD4 + T lymphocytes after stimulation with autoantigen (Ag) was significantly (>700-fold) increased with a concomitant increase in expression of the Foxp3 regulatory gene. Expression of OX40 was increased (maximum 11-fold) after allo-Ag via mixed-lymphocyte reaction response. CsA suppressed the upregulation of OX40 expression after allo-Ag in a dose-dependent manner. Taken together, these results suggest that the decrease in OX40 expression posttransplant includes the defective reconstitution of Treg cells, and the active inhibition of gene transcription by CsA.

Administration of cyclosporine after autologous bone marrow transplantation elicits a T-lymphocyte autoaggression syndrome with remarkable similarity to graft-versus-host disease (GVHD). This syndrome, termed syngeneic GVHD (SGVHD), with both acute and chronic phases, is mediated by a restricted repertoire of autoreactive T cells that promiscuously recognize major histocompatibility complex (MHC) class II determinants in association with a peptide from the invariant chain (MHC class II-invariant chain peptide; CLIP). This study evaluated and compared antigen-specific autoreactive T cells during acute and chronic SGVHD ex vivo isolated with a soluble MHC class II immunoglobulin molecular construct. This approach allows for the direct assessment of the functional behavior of the effector T cells without potential modification by in vitro culture. Two major subsets were detected that had overlapping specificity recognizing the MHC class II-binding domain of CLIP but that were differentially dependent on the N- and C-terminal flanking domains of this peptide. The N- and C-terminal subsets were primarily associated with acute and chronic SGVHD, respectively. The cytokine profiles of the CLIP-reactive T cells, however, were most informative and closely correlated with the onset and progression of disease. Levels of type 1 cytokine, particularly interferon-γ, messenger RNA (mRNA) production, assessed by quantitative polymerase chain reaction, were dominant during acute SGVHD, whereas chronic SGVHD was associated with type 2 cytokine mRNA production. Although there was a dramatic polarization with respect to cytokine production, only subtle changes in antigen specificity could be detected. Unexpectedly, the functional behavior within the antigen-specific effector cell populations is not fixed and seems to change as the disease progresses to the chronic phase. Concordant with the evolution of the effector T-cell response is a differential loss in B7.1 mRNA expression in the N-terminal CLIP-reactive T-cell subset that may reflect the regulation of this autoimmune response. Of additional interest, autoreactive T cells producing interleukin-10 mRNA were detected in both acute and chronic SGVHD, suggesting that this cytokine may play an important but perhaps paradoxical role in both the onset and progression of this experimental autoaggression syndrome.

Administration of the immunosuppressive drug cyclosporine A (CsA) following autologous stem cell transplantation paradoxically elicits a systemic autoimmune syndrome resembling graft-versus-host disease (GVHD). This syndrome, termed autologous GVHD, is associated with autoreactive CD8(+) T cells that recognize major histocompatibility complex (MHC) class II determinants in association with a peptide from the invariant chain. To investigate the potential role of cytokines and chemokines in autologous GVHD, interleukin 2 (IL-2), IL-4, IL-10, interferon gamma (IFN-gamma), and macrophage inflammatory protein-1alpha (MIP-1alpha) gene expression in peripheral blood mononuclear cells (PBMCs) was determined in 36 patients treated with CsA following transplantation and correlated with the induction of cytolytic activity against autologous phytohemagglutinin-stimulated lymphocytes (PHA-blasts) and the breast cancer cell line (T47D). The determination of gene expression by real-time polymerase chain reaction (PCR) revealed that IL-10 mRNA levels by PBMCs in patients with autologous GVHD were 29-fold higher than in healthy individuals. IFN-gamma (4-fold), IL-2 (3-fold), and MIP-1alpha (44-fold) mRNA levels were also increased in GVHD-induced patients compared with healthy individuals. The ability of PBMCs to lyse autologous PHA-blasts and T47D tumor cells exhibited an identical temporal relationship with expression of IL-10 and IFN-gamma during autologous GVHD. Moreover, the susceptibility to autologous GVHD as assessed in 75 patients was significantly associated with the IL-10(-1082) G/G polymorphic alleles, allelic variants in the promoter region that govern IL-10 production. These findings indicate that IL-10 may play an unexpected but critical role in autologous GVHD and could be utilized to enhance a graft-versus-tumor effect after transplantation. Interestingly, polymorphisms in the IL-10 promoter region may also explain differences in the susceptibility of patients to autologous GVHD induction.

Abstract 1009 Delayed immune reconstitution with increased risk of opportunistic infection is a major complication of HLA-haploidentical stem cell transplantation, especially in protocols employing extensive T cell depletion of the graft. Previous studies at our institution with high-dose, post-transplantation Cy (PT/Cy) have reported low rates of non-relapse mortality and serious opportunistic infections. Here we characterize immune reconstitution in fifty-three consecutive hematologic malignancies patients receiving nonmyeloablative conditioning, T cell-replete, HLA-haploidentical bone marrow transplantation (BMT), and graft versus host disease prophylaxis including PT/Cy. Patients with advanced hematologic malignancies (median age 51, range 14–71; 5 AML, 2 ALL, 4 MDS, 2 CML, 4 CLL, 1 CMML, 25 NHL, 7 Hodgkins, 3 mantle cell) received Cy 14.5 mg/kg/day IV on days −6 and −5, fludarabine 30 mg/m2/day IV on days −6 to −2, 200 cGy of TBI on day -1 and T cell replete bone marrow from donors with a median age of 44 (range 14–68). GVHD prophylaxis consisted of Cy (50 mg/kg/day) on days 3 and 4, mycophenolate mofetil for 30 days, and tacrolimus for 6 months. Grafts contained an infused median TNC/kg of 4.1 e8 (range 2.6–6.6 e8), CD3+/kg 3.6 e7 (range 1.7–6.7e7) and a CD34+/kg of 3.5e6 (range 1.4–7.0e6). Sustained engraftment of donor cells occurred in 86% of evaluable patients (44/51).The median times to neutrophil (>500/μL) and platelet recovery (>20,000/μL) were 17 days (range, 13–92 days) and 28 days (range, 13–580 days), respectively. Post-transplantation recovery of lymphocyte subsets is shown in Table 1 and Figure 1 and is notable for the following: 1) The median lymphocyte count at day 30 after transplantation is >180/ml and recovers to over 800/ml by day 60; 2) CD4+ T cell counts recover to a median >120/ml by day 60 and >220/ml by day 180 after transplantation; and 3) recovery of CD31+ recent thymic emigrants and CD45RA+ naïve T cells is delayed compared to recovery of memory T cells. T cell receptor spectratyping analysis on a subset of 10 patient/donor pairs chosen specifically for having no relapse/no GVHD (n=4), GVHD and no relapse (n=3), or late relapse (n=3) revealed that patients without relapse, GVHD, or recent viral infection had excellent reconstitution of the T cell repertoire to the level of the pre-transplant donor, as early as 6 months post-transplant (Figure 2). CMV specific T cell response using ELISPOT measured on a subset of 17 patients whose donors were reactive to CMV, revealed that donor-derived immunity to CMV returns by Day 60 in about 70% of patients (12/17) (Figure 3). In conclusion, immune reconstitution after non-myeloablative haploidentical T cell replete BMT with PT/Cy compares favorably with other reduced intensity conditioning alternative donor regimens and suggests that PT/Cy selectively preserves pathogen-specific memory T cells necessary to protect against infection. Further correlations of immune reconstitution with specific infectious and overall outcomes are being analyzed.Figure 1T-, B-, and NK-cell ReconstitutionFigure 1. T-, B-, and NK-cell ReconstitutionFigure 2T cell receptor spectratypingFigure 2. T cell receptor spectratypingFigure 3CMV-specific T cell frequencyFigure 3. CMV-specific T cell frequencyTable 1.Post-transplantation Lymphocyte Subset RecoveryMedian (cells/μL) (N)Interquartile range (cells/μL)ALCDonor1765 (46)1480–2100Recipient pre-BMT840 (45)425–1295Day 30184 (49)54–402Day 60820 (38)470–1260Day 180915 (34)670–1560Day 3653060 (22)820–2030CD3+CD4+CD45RA+ (naïve)Donor119 (33)82–189Recipient pre-BMT22 (34)4–38Day 300.33 (35)0.07–1Day 603 (29)1–9Day 18011 (23)5–31Day 36523 (13)13–92CD3+CD4+CD45RA−CCR7+ (central memory)Donor135 (33)95–158Recipient pre-BMT54 (34)11–79Day 302 (35)0.5–11Day 6034 (29)10–79Day 18061 (23)35–117Day 36589 (13)60–122CD3+CD4+CD45RA−CCR7− (effector memory)Donor187 (33)130–245Recipient pre-BMT87 (34)14–134Day 303 (35)1–18Day 6059 (29)14–122Day 180102 (23)43–179Day 365142 (12)64–204CD3+CD4+CD45RA+CD31+ (recent thymic emigrants)Donor61 (33)30–97Recipient pre-BMT6 (34)1–16Day 300.9 (35)0.03–0.4Day 601 (29)0.5–2Day 1804 (23)1–11Day 3657 (13)2–12CD3+CD4+Foxp3+Donor28 (33)23–35Recipient pre-BMT13 (34)6–24Day 301 (35)0.1–5Day 608 (29)4–16Day 18013 (23)7–25Day 36514 (13)7–17ALC, absolute lymphocyte count; WBC, white blood cell count; Treg, regulatory T cell Disclosures: Jones: Aldagen: Patents & Royalties.

The administration of cyclosporin A (CsA) after autologous stem cell transplantation (SCT) paradoxically elicits a systemic autoimmune syndrome that resembles graft-versus-host disease (GVHD); this is termed autologous GVHD (autoGVHD). Although dominated by activated CD8+ cytotoxic T lymphocytes, the complex cellular reaction also includes CD4+ T cells and involves multiple effector mechanisms. To determine the temporal development and relative importance of these mechanisms in autoGVHD, perforin/granzyme, Fas ligand (FasL), interferon-gamma (IFN-gamma), tumor necrosis factor (TNF)-alpha, and interleukin-18 gene expression in peripheral blood mononuclear cells was examined in 36 patients treated with CsA after SCT. Quantitative real-time polymerase chain reaction analysis revealed that perforin/granzyme B, TNF-alpha, and interleukin-18 messenger RNA (mRNA) levels in peripheral blood mononuclear cells from patients in whom autoGVHD developed were markedly higher (and temporally associated with the onset of autoaggression) compared with the levels detected in healthy individuals and in control, non-CsA-treated SCT patients. It is interesting to note that patients in whom autoGVHD did not develop also demonstrated increased mRNA levels for these cytokines: however, expression was substantially lower compared with that in patients with autoGVHD. It is important to note that IFN-gamma mRNA levels were selectively increased in CD8+ cells only from patients in whom autoGVHD developed. The development of autocytolytic T cells in autoGVHD correlated with increased expression of perforin, IFN-gamma, and TNF-alpha mRNA. Furthermore, enhanced autoreactive T-cell activity and the induction of autoGVHD was also concordant with perforin and TNF-alpha mRNA upregulation in CD4+ cells. Surprisingly, FasL mRNA levels were significantly decreased, with a progressive loss of FasL mRNA expression as autocytolytic activity increased. These findings suggest that IFN-gamma/perforin-based CD8+ cytotoxic T lymphocytes seem to play a dominant role in autoGVHD and that TNF-alpha/perforin-based CD4+ cells may amplify this autoaggressive syndrome. The FasL pathway may play an important role in the regulation of this immune syndrome.