Hyperimmunoglobulin prophylaxis, monitoring and preemptive ganciclovir treatment eliminate the risk of CMV infection to improve patient and renal allograft survival

This study was designed to investigate whether the introduction of ganciclovir to clinical use for anti-CMV treatment changes the risk of CMV infection in renal transplant patients. A total of 1545 cases who had received cadaveric renal transplants were divided into two groups: group 1 (n = 721) was made up of patients who received their transplants within 6 years before the introduction (1991) of ganciclovir and group 2 (n = 824), of individuals transplanted thereafter. Patient and graft survival of CMV D+/R- patients was uni- and multivariately compared with non-CMV D+/R- patients. In CMV D+/R- patients in group 1, survival was significantly lower, and their relative risk for graft loss was 1.32-fold (P = 0.0483) that of non-CMV D+/R- patients. In group 2 patient and graft survival was identical regardless of whether the patients were at risk for CMV infection or not. The risk of CMV infection can be eliminated by hyperimmunoglobulin prophylaxis, CMV monitoring and preemptive ganciclovir treatment in renal transplant patients.

Aggressive treatment of the first acute rejection episode using first-line anti-lymphocytic preparation reduces further acute rejection episodes after human kidney transplantation

The detrimental effect of acute rejection episodes on long-term outcome of renal allografts in cyclosporin-treated patients is well established, although has not been seen by all investigators. To analyse the possibility that aggressive treatment of the first episode may ameliorate this detrimental effect, we performed an open label, randomised prospective trial in cyclosporin-based, immunosuppressed recipients of postmortem renal allografts in order to compare two different treatment protocols during primary acute rejection episodes: (1) group 1 of 25 patients received 3 x 250 mg methylprednisolone (MP) i.v.; (2) group 2 of 25 patients received 7 x anti-thymocyte globulin (ATG)-Fresenius i.v. (4 mg/kg body weight). During a period of 4 years, the following clinical observations were made: (1) The incidence of an acute re-rejection episode was significantly reduced in the ATG-treated study group (16%) compared to the MP-treated study group (72%); (2) The severity of the first acute rejection episode (intensity of renal dysfunction measured in terms of 10-day creatinine area under curve) showed no significant difference between the groups (37 mg x 10-d/dl to 58 mg x 10-d/dl); and (3) The half-lives of allografts in both groups have not shown any significant differences so far. In conclusion, aggressive treatment of the first rejection episode of renal allografts with the use of ATG reduced the incidence of re-rejection episodes which, however, are not reflected so far by improvement of the 4-year survival rate of these allografts. Since it could be observed that re-rejection is an even worse predictor for chronic transplant failure, a better long-term outcome of renal allografts in ATG-treated patients may be expected during a longer observation period. The incidence of a third episode was also reduced in the ATG-treated group (0%) compared to the MP-treated group (12%).

Mycophenolate mofetil-based, cyclosporine-free induction and maintenance immunosuppression: first-3-months analysis of efficacy and safety in two cohorts of renal allograft recipients

BACKGROUND

The currently used macrolide immunosuppressants, i.e., cyclosporine and tacrolimus, exert considerable nephrotoxicity. We aimed to avoid the nephrotoxic effects by applying a cyclosporine-free regimen for the induction as well as for the maintenance treatment of renal allograft recipients using mycophenolate mofetil (MMF) as the primary immunosuppressant.

METHODS

Thirteen patients were converted from cyclosporine (CsA) to MMF monotherapy. For 4 weeks, MMF (2 g/day) was added to the CsA treatment, before CsA was tapered by weekly steps of 25 mg/day and without "safeguard treatment" with additional immunosuppressants. In a second approach, 12 patients older than 50 years, and receiving a renal graft from a donor older than 50 years, were treated primarily with MMF combined with steroids and an induction therapy using antithymocyte globulin, and without the addition of CsA.

RESULTS

Thirteen long-term renal transplant patients could be converted from CsA to MMF monotherapy. Conversion resulted in an immediate and long-lasting improvement of their median creatinine values by 20%. No serious adverse events occurred. In the second cohort of 12 patients, MMF was used as the primary immunosuppressant. All patients are alive and no grafts were lost after 4 months (n= 12) and after 6 months (n=7). The median creatinine values achieved after 4 and 6 months were 1.16+/-0.25 and 1.30+/-0.21 mg/dl, respectively. One patient was converted to CsA because of a reversible rejection episode (8.3%), and another patient was converted because of cytomegalovirus disease. Major complications consisted of wound-healing disturbances (16.6%) and cytomegalovirus infections (41.6%).

CONCLUSION

MMF monotherapy can be safely applied as long-term maintenance immunosuppression with improvement of renal function. Steroids are not required as an adjunct to MMF. MMF monotherapy, in the absence of drug-related nephrotoxicity, is particularly beneficial for grafts derived from marginal donors, such as donors of advanced age.

Restricted T cell V beta repertoire in renal allografts during acute and chronic rejection

Allo-MHC specific antigen recognition might not only be involved in acute, but also in chronic rejection. The clonotypic specificity of the T-cell receptor to recognize all-MHC is located in the variable (V) alpha and beta chain. A restricted T-cell receptor repertoire could support an immunological basis for chronic rejection. The novel feature of this study is that V beta repertoire was assessed in ongoing chronic rejection before end-stage renal failure and in acute rejection. V beta s 1 to 20 were quantitated by PCR in PBMC and biopsies of rejecting renal allografts. The V beta pattern in PBMC demonstrated a polyclonal distribution. However, the intragraft V beta repertoire was restricted to 1 to 3 dominant V betas and highly individual in 9 of 12 patients. Number and type of the HLA mismatch and the time interval between transplantation and biopsy did not correlate to the V beta distribution. The individual response is attributed to genetic predisposition factors of the recipient. Therefore, the restriction of the V beta repertoire indicates allo-MHC dependent immune processes not only in acute, but also in ongoing chronic rejection. Tailor-made antibodies against dominant V betas might offer specific individual immunosuppression in treating both acute and ongoing chronic rejection.

Mycophenolate mofetil in patients with acute renal failure: evidence of metabolite (MPAG) accumulation and removal by dialysis

Pharmacokinetics of mycophenolic acid (MPA) was analyzed in eight patients with post-transplant acute renal failure. Furthermore, the effect of hemodialysis upon blood levels of MPA and its major metabolite, MPA glucuronide (MPAG), was determined. The mean duration of the posttransplant renal failure was 18 days, but renal function resumed in all patients eventually. The patients were treated with 3 g/day of mycophenolate mofetil for 28 consecutive days combined with cyclosporine A, methylprednisolone, and ATG for induction therapy. In all patients, accumulation of MPAG but not of MPA was observed. MPA trough levels were in the range between 0.5 microgram/ml at day 2 and 2.3 micrograms/ml at the end of the study period. However, this concentration difference did not reach statistical significance. Trough levels of MPAG accumulated, reaching levels as high as 358 micrograms/ml. However, with increasing recovery of renal function, MPAG levels fell to a median trough concentration of 141 micrograms/ml. MPAG, but not MPA, could partially be removed from the circulation by hemodialysis treatment.

The immunosuppressive effects of verapamil upon mitogen activated and allo-antigen inducible human cytotoxic T-lymphocytes

In this study, the effect of verapamil, a phenylalkylamine-type Ca2+ antagonist, upon the activation of human mononuclear cells was investigated and a detailed analysis of the kinetics and dose related effects of verapamil upon alloreactive cytotoxic T-cells (CTL) was undertaken. Verapamil suppressed the release of interleukin-2, proliferation and generation of CTL activity in mitogen and alloantigen stimulated human T-lymphocytes in a dose related fashion. Verapamil suppressed the steady state levels of several T-cell activation-associated gene transcripts, i.e. the mRNA encoding for interleukin-2, and a cytotoxic T-cell specific serine esterase. Verapamil exerted a novel immune-suppressive effect, i.e. the inhibition of mature alloantigen-inducible cytolytic T-cells, thus rendering verapamil a progenitor of potent and clinically useful immunosuppressive drugs.

Evidence that functional deletion of donor-reactive T lymphocytes in kidney allograft recipients can occur at the level of cytotoxic T cells, IL-2-producing T cells, or both. A limiting dilution study

The frequencies of circulating donor-reactive cytotoxic lymphocyte precursors (CLP) and Il-2-producing helper lymphocyte precursors (HLP) were determined by limiting dilution analysis in 19 kidney allograft recipients before and at various intervals (up to 2 years) after transplantation. A significant, selective, and stable reduction of the frequencies of donor-reactive (but not of third party-reactive) CLP and/or HLP was observed in some patients beginning 3 to 6 months after transplantation. One patient developed reduced frequency of CLP only, 3 patients reduced frequencies of HLP only, and 2 patients reduced frequencies of both CLP and HLP. The selective reduction of donor-reactive CLP and/or HLP frequencies ranged from 5-25-fold when compared with the pretransplantation level and was associated with stable graft function. These data indicate that functional deletion of circulating donor-reactive T cells can occur at the level of cytotoxic T lymphocytes, Il-2-producing helper T lymphocytes, or both. Implications of these findings for the individualization of immunosuppressive regimens will be discussed.

Tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6 expression in inflammatory bowel disease

The etiology of ulcerative colitis (UC) and Crohn's disease (CD) remains enigmatic. Infiltrating intestinal macrophages are capable of producing the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and interleukin-6 (IL-6). We investigated the presence of IL-6, TNF-alpha and IL-1 beta mRNA transcripts in inflammatory bowel disease (IBD), normal, and other inflammatory intestinal specimens utilizing the polymerase chain reaction (PCR). TNF-alpha mRNA levels did not very between inflammatory bowel disease and control specimens. IL-1 beta mRNA levels were highest in active UC and noninflammatory bowel disease inflammatory specimens while IL-6 mRNA levels were highest in active IBD specimens. Infiltrating T cells, macrophages, and B cells were identified as sources of IL-6 protein in inflammatory bowel disease specimens by immunofluorescent staining. IL-6 transcripts were elevated only in active inflammatory bowel disease specimens, suggesting that IL-6-mediated immune processes are ongoing in the inflammatory mucosal environment of CD and UC.

[Baclofen intoxication in chronic hemodialysis and kidney transplantation]

Fourteen days after renal transplantation, at first gave with good transplant function, a 36-year-old woman developed neurogenic dysfunction of bladder emptying. This was treated with baclofen, 5 mg three times daily by mouth. Between the 7th and 10th treatment day she progressively developed an organic psychotic syndrome and increasing respiratory paralysis after the onset of renal failure, associated with rejection of the transplanted kidney which required dialysis. Plasma concentration of baclofen was 565 ng/ml (therapeutic range 80-400 ng/ml). After discontinuing the drug and renewed haemodialysis the baclofen level rapidly fell and the symptoms receded. In a second case, a 57-year-old man on dialysis developed a thalamic pain syndrome after an intracerebral haemorrhage in the region of the basal ganglia. He was given four times 10 mg baclofen by mouth over 24 hours. 24 hours after the first dose he became deeply unconscious with respiratory failure. Plasma concentration of baclofen after the first haemodialysis period was 480 ng/ml. After 48 hours of artificial ventilation it was possible to extubate; a symptomatic transitory psychotic syndrome disappeared within 4 days. Both patients had pre-existing cerebral damage in addition to the chronic renal failure (in the first patient, meningoencephalitis 30 years previously with persisting focal lesions in the computed tomogram CT]; in the second one, residual lesions in the CT after intracerebral haemorrhage). It is emphasized that in patients who are in renal failure baclofen treatment should be undertaken cautiously: toxic signs can quickly develop especially if there is pre-existing cerebral damage.

Abrogation of glucocorticoid-mediated inhibition of T cell proliferation by the synergistic action of IL-1, IL-6, and IFN-gamma

Glucocorticoids (GCS) inhibit the transcription of multiple activation-associated cytokine genes. By Northern blot analysis now we demonstrate that antiproliferative concentrations of dexamethasone and 6 alpha-methylprednisolone block mitogen-induced IL-2 gene expression in human peripheral blood mononuclear leukocytes in a concentration-dependent fashion. In addition, using a mitogen-induced proliferation assay of human peripheral blood mononuclear leukocytes, we show that GCS-mediated anti-proliferative effects are not blocked by rIL-1, rIL-2, rIL-3, rIL-4, rIL-5, rIL-6, rTNF-alpha, rTNF-beta, and rIFN-gamma, individually at 1 to 1000 U/ml, but are totally abrogated, in a concentration-dependent fashion, by the combination of rIL-1, rIL-6, and rIFN-gamma (25 to 50 U/ml for each cytokine). Thus, blockade of cytokine expression is the primary mechanism by which GCS inhibit mitogen-driven and alloantigen-induced T cell proliferation. The immunosuppressive effects of GCS are almost certainly exacted at the level of cytokine gene transcription.

Abrogation of glucocorticoid-mediated inhibition of T cell proliferation by the synergistic action of IL-1, IL-6, and IFN-gamma

Glucocorticoids (GCS) inhibit the transcription of multiple activation-associated cytokine genes. By Northern blot analysis now we demonstrate that antiproliferative concentrations of dexamethasone and 6 alpha-methylprednisolone block mitogen-induced IL-2 gene expression in human peripheral blood mononuclear leukocytes in a concentration-dependent fashion. In addition, using a mitogen-induced proliferation assay of human peripheral blood mononuclear leukocytes, we show that GCS-mediated anti-proliferative effects are not blocked by rIL-1, rIL-2, rIL-3, rIL-4, rIL-5, rIL-6, rTNF-alpha, rTNF-beta, and rIFN-gamma, individually at 1 to 1000 U/ml, but are totally abrogated, in a concentration-dependent fashion, by the combination of rIL-1, rIL-6, and rIFN-gamma (25 to 50 U/ml for each cytokine). Thus, blockade of cytokine expression is the primary mechanism by which GCS inhibit mitogen-driven and alloantigen-induced T cell proliferation. The immunosuppressive effects of GCS are almost certainly exacted at the level of cytokine gene transcription.

The role of interleukin-6 in mitogenic T-cell activation: detection of interleukin-2 heteronuclear RNA by polymerase chain reaction

It has been documented that interleukin-6 (IL-6) supports the proliferation of purified, anti-CD3-stimulated murine T cells. We found that stimulation of human peripheral blood mononuclear cells (PBMCs) with anti-CD3 induced a significant accumulation of IL-6 mRNA, indicating that antigen-mediated T-cell activation may involve IL-6 release from accessory cells. Phytohemagglutinin (PHA) had little effect upon IL-6 gene expression. In keeping with these findings, anti-IL-6 reduced but did not abolish anti-CD3-mediated proliferation of PBMCs, but had no significant effect upon PHA-stimulated proliferation. The addition of recombinant (r) IL-6 enhanced the proliferation of anti-CD3-stimulated PBMCs and increased the accumulation of IL-2 mRNA in PHA-stimulated PBMCs during the first 5 hr of culture. Nuclear run-off experiments did not reveal significant changes in IL-2 transcription in PHA plus rIL-6-treated PBMCs attempting to assume that IL-6 mediates stabilization of IL-2 mRNA. However, monitoring of partially spliced IL-2 mRNA by polymerase chain reaction revealed a clear increase in IL-2 heteronuclear RNA. Thus IL-6 increases the rate of IL-2 transcription which was not detectable by conventional in vitro transcription assays. We conclude that anti-CD3 triggers T-cell proliferation through a process that is partially but not entirely dependent upon release of IL-6. IL-6, in turn, supports IL-2 transcription. Insofar as anti-CD3 mimics antigen-triggered activation of the T-cell receptor complex, IL-6 appears to support the early immune response by augmenting antigen-triggered IL-2 gene expression.

The molecular basis for the synergism between the CD3/alpha beta T cell receptor and the CD2 antigen-derived signals in promoting T-cell proliferation

Northern blot analysis and a highly sensitive methodology for mRNA phenotyping, polymerase chain reaction (PCR), were used to explore the basis for the synergism between CD3/alpha beta T cell receptor (TCR) and the CD2 antigen-derived signals in promoting proliferation of T cells. Northern blotting of RNA isolated from highly purified normal human T cells revealed that crosslinking of anti-TCR-1 (a mAb directed at a framework determinant of the TCR) and OKT11 (a mAb directed at the SRBC-binding epitope of the CD2 antigen) induced the expression of the interleukin-2 gene and the gene for IL-2 receptor alpha, mRNA phenotyping by PCR revealed that crosslinkage of TCR with the CD2 antigen, and not independent crosslinking of TCR or the CD2 antigen, results in the induction of IL-2, IL-2 receptors alpha and beta, and IL-4-specific transcripts. Highly purified CD4+ T cells, as well as CD8+ T cells proliferated by crosslinking TCR with CD2 antigen. Moreover, crosslinkage of TCR with the CD2 antigen and not of either antigen with the CD4 antigen (on the surface of CD4+ T cells) or the CD8 antigen (on the surface of CD8+ T cells) resulted in marked proliferation. Our demonstration that the CD2 antigen-derived signal(s) contribute to the expression of growth promoting genes elicited via the TCR, and that the CD2 antigen is more efficient compared with the CD4 or CD8 antigen in evoking T cell proliferation, suggests that autoimmunity as well as alloimmunity might be regulated by targeting the CD2 antigen.

Transcriptional modulation of human IL-6 gene expression by verapamil

Calcium channel-blocking agents interfere with the initial increase of cytosolic calcium that follows mitogenic stimulation of T lymphocytes. In cultures of mitogen-stimulated PBMC, verapamil also blocked T cell accumulation of cytoplasmic IL-2-encoding mRNA. In sharp contrast, the addition of verapamil to PHA and PMA-stimulated PBMC augmented the mitogen-stimulated increases in nuclear transcription of IL-6-encoding mRNA, steady state levels of IL-6 encoding mRNA, and release of IL-6 bioactivity. These experiments indicated that an increased IL-6 transcriptional rate rather than stabilization of transcripts accounted for the increased cytoplasmic IL-6 mRNA levels and subsequent expression of IL-6 bioactivity. These effects were not produced by nicardipine, another potent calcium channel blocker, or EGTA. We suggest that a non-calcium-dependent, IL-6 regulatory factor, absent or inactive in verapamil-treated cultures, inhibits IL-6 gene activation in mitogen-stimulated PBMC. Failure to express this inhibitory factor would result in IL-6 gene superinduction at a transcriptional level.

Physiologic signaling in normal human T-cells: mRNA phenotyping by northern blot analysis and reverse transcription-polymerase chain reaction

Synergy between ionomycin and sn-1,2-dioctanoylglycerol (diC8) was shown at the level of lymphokine gene transcription. Transcriptional activation of interleukin-2 (IL-2), interferon-gamma (IFN-gamma), and the protooncogene H-ras was accomplished by signaling highly purified normal human resting T-lymphocytes (T-cells) with diC8, a physiologic regulator of protein kinase C, and the calcium ionophore, ionomycin. Northern blot analysis of mRNA for early T-cell activation genes demonstrated the synergism between diC8 and ionomycin at the gene induction level. To amplify very low levels of IL-2 mRNA, sequential reverse transcription and polymerase chain reaction (RT-PCR) of T cell mRNA were used to demonstrate the capacity of the calcium signal (ionomycin) to promote low-level IL-2 transcription in normal human T-cells without additional signals. Cyclosporine (CsA) prevented diC8 and ionomycin-induced expression of IL-2, IFN-gamma, and H-ras genes. The completeness of its inhibitory effect was evident by the absence of IL-2 transcripts in CsA-treated cultures screened by the RT-PCR technique. CsA also prevented IL-2 and IFN-gamma gene expression in accessory cell-depleted T-cells stimulated by cross-linking the CD2 and CD3 antigens on the cell surface. Our observations demonstrate that a physiologic regulator of PKC, diC8, and cell surface crosslinking of the CD2 and CD3 antigen, promote gene expression in normal human quiescent T-cells independently of accessory cells, and that CsA prevents gene expression via a direct effect on T-cells.

Transcriptional modulation of human IL-6 gene expression by verapamil

Calcium channel-blocking agents interfere with the initial increase of cytosolic calcium that follows mitogenic stimulation of T lymphocytes. In cultures of mitogen-stimulated PBMC, verapamil also blocked T cell accumulation of cytoplasmic IL-2-encoding mRNA. In sharp contrast, the addition of verapamil to PHA and PMA-stimulated PBMC augmented the mitogen-stimulated increases in nuclear transcription of IL-6-encoding mRNA, steady state levels of IL-6 encoding mRNA, and release of IL-6 bioactivity. These experiments indicated that an increased IL-6 transcriptional rate rather than stabilization of transcripts accounted for the increased cytoplasmic IL-6 mRNA levels and subsequent expression of IL-6 bioactivity. These effects were not produced by nicardipine, another potent calcium channel blocker, or EGTA. We suggest that a non-calcium-dependent, IL-6 regulatory factor, absent or inactive in verapamil-treated cultures, inhibits IL-6 gene activation in mitogen-stimulated PBMC. Failure to express this inhibitory factor would result in IL-6 gene superinduction at a transcriptional level.

Evidence that glucocorticosteroids block expression of the human interleukin-6 gene by accessory cells

The mode of action of glucocorticosteroids as immunosuppressive and antiinflammatory agents is not fully understood. Glucocorticosteroids block synthesis of interleukin 1 by interfering with the transcription of the IL-1 beta gene. Glucocorticosteroids may also induce rapid degradation of IL-1 mRNA. In the presence of antigen, IL-1 is a potent accessory-cell-derived growth and differentiation co-factor for stimulating resting T lymphocytes. The recently defined interleukin 6 protein is even more powerful than IL-1 in promoting T cell growth and differentiation and acts synergistically with IL-1. Like IL-1, IL-6 is produced by accessory cells and exhibits pleiotropic functions. We herein describe the effects of glucocorticosteroids on IL-6 synthesis. We provide evidence that glucocorticosteroids prevent IL-6 gene transcription in human peripheral blood mononuclear cells.

A kinetic analysis of the effects of interleukin-2 diphtheria toxin fusion protein upon activated T cells

The interleukin-2 diphtheria toxin-related fusion protein (IL-2 toxin) inhibits protein and DNA synthesis IN rIL-2 (10(-10) M) stimulated T lymphoblasts in a dose-dependent fashion. However, prior to target cell death very low concentrations of rIL-2 and IL-2 toxin synergistically stimulate [3H] thymidine incorporation despite inhibition of [14C] leucine uptake. A sequential analysis of [3H] thymidine incorporation shows that high IL-2 toxin concentration (10(-9)-10(-7) M) stimulates DNA synthesis at 18 hr of culture and inhibits [3H] thymidine uptake after 24 hr, while low concentrations of IL-2 toxin (10(-12)-10(-10) M) exhibits stimulatory effects only after 24 hr of culture. Anti-Tac a monoclonal antibody directed against the p55 chain of the high affinity IL-2 receptor (IL-2R) blocks the stimulatory effects of high-dose IL-2 toxin, thereby proving that these effects are mediated through the IL-2 domain of the fusion protein. At 7 hr following interaction with IL-2R receptor (IL-2R)+ T cells, IL-2 toxin-treated cells evidence augmented transcription of the heat shock protein gene, an effect indistinguishable from those mediated by rIL-2. We conclude that interaction of IL-2 toxin with IL-2R+ T cells initially mimicks the stimulatory effects of IL-2 upon gene transcription and DNA synthesis yet concomitant inhibition of protein synthesis is evident.

Possible association of the immunosuppressive and B cell lymphoma-promoting properties of cyclosporine

Central to the immunosuppressive properties of cyclosporine is a drug imposed blockade of the interleukin-2 gene activation. As IL-6 stimulates antigen-activated T cells to release IL-2, we examined the influence of CsA on IL-6 gene expression and IL-6-supported T cell proliferation. Northern blot analysis revealed that CsA failed to abolish IL-6 gene expression in mitogen-activated peripheral blood mononuclear cells. In fact, increased IL-6 gene transcription and increased release of IL-6 bioactivity were detected using mitogen-activated PBMCs cultured with CsA doses (200-800 ng/ml) only slightly in excess of the minimal antiproliferative dose. CsA completely abrogated the IL-6-stimulated proliferative responses of macrophage-depleted T cells stimulated with polyvalent anti-CD3 monoclonal antibodies. It is interesting that CsA-treated patients evidence an increased incidence of polyclonal lymphoproliferative disorders and B cell lymphomas. As IL-6 fosters B cell activation and growth of EBV-transformed B cells, excessive CsA doses may support development of EBV-transformed B cell lymphomas via superinduction of the IL-6 gene.

Sequential effects of interleukin 2-diphtheria toxin fusion protein on T-cell activation

The interleukin 2-diphtheria toxin-related fusion protein (IL-2-toxin) rapidly inhibits protein synthesis in IL-2 receptor (IL-2R)-bearing phytohemagglutinin-activated T cells but transiently stimulates DNA synthesis. At 7 hr after interaction with IL-2R+ phytohemagglutinin-activated T cells, IL-2-toxin-treated cells bear augmented steady-state levels of c-myc, interferon gamma, and IL-2R mRNA; these effects are indistinguishable from those produced by recombinant IL-2. Amplification of IL-2 sequences by the polymerase chain reaction reveals an increased level of IL-2 mRNA in cell cultures treated with recombinant IL-2, IL-2-toxin, and cycloheximide. These results suggest that IL-2-toxin can affect de novo IL-2 gene transcription/mRNA stabilization through independent mechanisms exerted by both the IL-2R binding domain and ADP-ribosyltransferase activity of the fusion protein. After 20 hr of culture, IL-2R mRNA was markedly decreased in both IL-2-toxin- and cycloheximide-treated phytohemagglutinin-activated T cells. Although interaction of IL-2-toxin with IL-2R+ T cells initially mimics the stimulatory effects of IL-2 upon c-myc, interferon gamma, IL-2R, and IL-2 gene expression, the consequences of inhibition of protein synthesis mediated by the ADP-ribosyltransferase activity of the toxin dominate after 7 hr and are indistinguishable from those effects mediated by cycloheximide.

Similar effects of cyclosporine and verapamil on lymphokine, interleukin 2 receptor, and proto-oncogene expression

Since calcium channel blocking agents and CsA exert an antiproliferative effect upon T cell mitogenesis, we have compared and characterized their immunosuppressive properties at the level of gene activation. Verapamil (greater than or equal to 30 microM), which blocks T cell mitogenesis and a rise in cytosolic calcium, was added to cultures of peripheral blood mononuclear cells stimulated with phytohemagglutinin (5 micrograms/ml) and phorbol myristate acetate (5 ng/ml). Northern blot analysis was performed using cDNA probes for the p55 interleukin 2 receptor (Tac; IL-2R), interleukin 2 and c-myc at 20 hr of culture. Accumulation of IL-2 encoding mRNA within the cytoplasm was completely abrogated by verapamil. However, IL-2R and c-myc encoding mRNA were clearly detectable in verapamil-treated cell cultures. Surface expression of the Tac protein in mitogen-activated T cells was also not blocked by verapamil as shown by FACS analysis. In companion experiments with CsA, verapamil only partially inhibits the intracellular processes leading to T cell activation. A calcium-independent pathway may exist for the expression of IL-2R and c-myc, while an increase of intracellular Ca2+ may provide the additional signal for IL-2 gene expression. Although the in vitro concentrations of verapamil used in these experiments are in excess of common clinically therapeutic levels, the results help clarify the mode of CsA action and may provide a new tool to dissect the early events of T cell activation.

Quantitative assessment of interleukin-2-producing alloreactive human T cells by limiting dilution analysis

A limiting dilution (LD) culture system was developed to estimate the frequency of IL-2 producing alloantigen-reactive human helper T lymphocytes (HTL). E rosette-purified T cells or cell sorter-separated CD4+ and CD8+ subsets were co-cultured under LD conditions with irradiated allogeneic Epstein-Barr virus-transformed lymphoblastoid cell lines (LCL) in the absence of additional growth factors. IL-2 in microculture supernatants was detected in a bioassay combined with rapid colorimetric visualization (cleavage of MTT). Under these conditions, one out of 250-800 E+, 180-280 CD4+, and 440-1000 CD8+ T cells produced IL-2 after a culture period of 3 days. This quantitative analysis of alloantigen-specific human HTL is complete within 4 days and thus provides a rapid method with potential applications in various clinical situations, e.g., transplantation medicine.

[Infectious complications in immunosuppressed patients after kidney transplantation]

Under an immunosuppressive therapy after renal transplantation there is an increased risk of acquiring infections with a possible lethal outcome. On the basis of 4 cases it is shown that invasive diagnostic procedures are indicated when the primary noninvasive methods and therapeutical trials are unsuccessful. Early and consequent therapy of severe infections must imply the reduction or cessation of immunosuppression. Conservation of the transplant at any price is not justifiable.

[Evaluating transplant kidneys: nuclear magnetic resonance tomography in comparison with sonography]

In a prospective study we compared the results of MRI and ultrasound in assessing renal dysfunctions in 22 patients with renal allografts. The current diagnostic criteria are presented and the range of indications is evaluated in relation to perfusion scans.

Human cytotoxic T lymphocytes. II. Frequency analysis of cyclosporin A-sensitive alloreactive cytotoxic T-lymphocyte precursors

A limiting dilution (LD) culture system was used to investigate the effect of cyclosporin A (CsA) on the activation and differentiation of human alloreactive cytotoxic T-lymphocyte precursors (CTL-p). CsA reduced in a dose-dependent fashion the frequency of alloantigen-inducible CTL-p. With most normal individuals tested there was a 20- to 50-fold reduction of alloreactive CTL-p frequencies in the presence of 500-1000 ng/ml CsA. Both unseparated T cells and CD8+ T cells were CsA-sensitive under LD culture conditions. Importantly, however, alloreactive CTL-p from two out of 21 normal individuals were found to be largely CsA-resistant. CsA did not affect the growth of MLR-primed CTL in secondary LD culture. Furthermore, CsA slightly inhibited the cytolytic activity of some alloantigen-specific CTL clones. These results are discussed with respect to the clinical use of CsA in transplantation medicine.

Selective reduction of donor-specific cytotoxic T lymphocyte precursors in patients with a well-functioning kidney allograft

We have recently developed a sensitive limiting dilution (LD) culture system to measure human alloreactive cytotoxic T lymphocyte precursors (CTL-p) in a given lymphoid cell population. We have now used this system to determine frequencies of donor HLA antigen-inducible CTL-p in the peripheral blood of human allograft recipients at various stages after transplantation. All patients (1 pancreas recipient and 9 kidney recipients) were on continuous cyclosporine treatment throughout the study. We report that, in patients with a well-functioning kidney graft (6/9), the number of donor-reactive CTL-p among peripheral blood lymphocytes decreased within 3-8 months after transplantation--in some cases (2/6) more than 10-fold. In contrast, frequencies of CTL-p with specificity for third-part HLA antigens remained largely unaltered in these patients. Furthermore, no decrease of donor-reactive CTL-p frequencies was seen in 3 of 4 patients showing clinical symptoms of graft rejection. These results indicate that functional clonal deletion of antigraft-reactive CTL-p may contribute to the state of graft tolerance in certain patients with a well-functioning kidney allograft.

An inherited deficiency of the third component of complement, C3, in guinea pigs

Hereditary deficiency of the third component of complement, C3, is found very seldom in the human. C3 deficiency is associated with severe bacterial infections revealing the central role of C3 in complement activation via the classical or alternative pathway. We describe a new hereditary C3 deficiency in strain 2 guinea pigs. Serum from these animals had a markedly reduced lytic activity in a standard assay for complement-dependent, antibody-mediated cytotoxicity. In functional assays of individual components, the hemolytic activity of the components C4, C2, C5 and of factors B, D and H was in the normal range. The functional C3 titer, and similarly C3 antigenic activity in the serum of these C3-deficient animals (C3D) was on average only 5.7% of normal activity. Typing the animals with alloantisera or monoclonal antibodies to guinea pig Ia-antigens revealed that the C3D animals had the major histocompatibility complex-haplotype of inbred strain 2 guinea pigs (B.1, Ia.2,4). The C3 defect is not linked to the major histocompatibility complex and, in addition, is not linked to a C3a receptor deficiency. Macrophages and hepatocytes of the C3D animals have an unimpaired capacity for synthesis and secretion of C3 as measured by enzyme-linked immunosorbent assay. There was no indication for hypercatabolism of normal C3 by the animals as shown by plasma clearance of 125I-radiolabeled C3. Thrombocytes of the C3D animals responded normally to stimulation with purified C3a in an ATP-release assay without an indication for a desensitization in vivo. Possibly the fault resides in an enhanced susceptibility of their own C3 to proteolysis. However, C3 partially purified from the plasma of the C3D animals or secreted by hepatocytes exhibited no obvious structural differences to purified normal C3 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis or in immunoblotting. The C3D serum had a reduced bactericidal activity compared to normal or to C4-deficient serum. Nevertheless, the animals are apparently healthy without an indication for increased frequency of bacterial infections. These guinea pigs provide an unique model for analysis of the biological functions of C3 in vivo and in vitro without the need for artificial C3-depletion procedures with all their known and unknown side-effects.

Human cytotoxic T lymphocytes. I. Limiting-dilution analysis of alloreactive cytotoxic T-lymphocyte precursor frequencies

A limiting-dilution system was established to measure the frequency of alloreactive cytotoxic T-lymphocyte precursors (CTL-p) in human peripheral blood T cells. Culture medium supplemented with recombinant interleukin-2 enabled clonal expansion of all CTL-p stimulated by allogeneic peripheral blood or spleen cells. The range of CTL-p frequencies in fully HLA-mismatched responder-stimulator combinations was 1:240 to 1:1230. Split-well analysis of individual microwells showed that the cytotoxic T-cell clones generated under limiting-dilution conditions showed exquisite specificity for the stimulating alloantigens. Alloreactive CTL-p were enriched in the OKT4- T-cell subset. This limiting-dilution system was highly reproducible and can thus be applied to investigate human cytotoxic T-cell precursor frequencies in various clinically relevant situations.

Low zone desensitization: a stimulus-specific control mechanism of cell response. Investigations on anaphylatoxin-induced platelet secretion

The biologic activity of the anaphylatoxic peptides C5a and C3a is regulated efficiently at the target-cell level by the phenomenon of desensitization. Desensitization of platelets is stimulus specific and can be induced by low concentrations of anaphylatoxins without any preceding secretory event. In contrast to activation to secretion, desensitization is Ca++ independent but much more time consuming, especially at lower temperatures where both processes differ markedly in reaction velocity. This low zone desensitization insures that secretion from platelets only occurs when high amounts of anaphylatoxins are rapidly generated in the vicinity of the target-cell. Consequently, stimulus-specific unresponsiveness of the target cells can be induced by slowly increasing the concentration of the respective stimuli in their vicinity. Cellular control seems to act as a first-line mechanism of regulation, whereas the role of fluid-phase control is considered as preventing longer persistence and systemic accumulation of active anaphylatoxins.