Graft-versus-host and graft-versus-tumoreffects: Walking the fine line

Transplantation of allogeneic hematopoietic cells is an effective therapy for a number ofmalignant and non-malignant diseases. It can allow one to give chemotherapy and/or radiationtherapy at doses that would be potentially lethal if one had to depend on the recovery of the patient’sown marrow stem cells. It can allow replacement of defective hematopoietic stem cells. But it canalso induce graft-versus-host disease (GVHD): the transplantation of immunologically competentcells from another person can lead to immunologic assault upon the recipient’s skin, gut, liver, andother organs. This isn’t always all bad, in that the immunologic attack may also include the abnormalcells responsible for the patient’s illness—often called “graft-versus-leukemia” (GVL) effect,because chronic myeloid leukemia is one of the diseases where this effect is most prominent andmost beneficial. Unfortunately, the two effects are not entirely separate; in many contexts, thepresence of GVHD is a predictor of GVL effect. It has for several years been something of a “HolyGrail” quest in transplantation medicine to try to learn how to exploit GVL effect without producingsevere GVHD.

The pathophysiology of acute GVHD involves dysregulation of inflammatory cytokine cascadesand donor T cell responses to host alloantigens. Interleukin 18 (IL-18) is a recently discoveredcytokine that has potent immune modulatory effects. It is unlike most other cytokines, in that it caninduce either a Th1 or Th2 polarization depending on the immunological context. IL-18 is elevatedin the serum in acute GVHD, but exactly what it does in that syndrome is just beginning to beunderstood. In experimental models, its Th1 effect reduces the severity of acute GVHD whenadministered early after BMT. Interestingly, when administered instead to thedonors it can alsoreduce the severity of acute GVHD—but now it does it as a Th2-inducing cytokine. Most promisingof all, despite reducing the severity of acute GVHD, in some models it preserves the GVL effectafter BMT. It thus appears that learning to manipulate IL-18 might allow us to make stem-celltransplantation both safer and more effective. Our knowledge in this area is reviewed this month ina paper byDrs Pavan Reddy and James L. M. Ferrara of the University of Michigan Cancer Center;that paper may be found beginning on page 365.

doi:10.1016/S0022-2143(03)00085-4

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LABORATORY and

CLINICAL MEDICINECopyright © 2003 by Mosby, Inc.

VOLUME 141 NUMBER 6JUNE 2003

THIS MONTH IN J Lab Clin MedIssue Highlights for June 2003

361

Wilson’s disease and lipid peroxidation:Zinc to the rescue, again

Wilson’s disease is a rare metabolic disorder in which copper accumulation leads to neurologicand hepatic consequences, and in which severe oxidative hemolysis may occur. Excess copper maybe mobilized by penicillamine, a chelating drug with a number of problematic toxicities. It is nowrecognized that zinc supplementation can lead to enough induction of metallothionine to create anegative copper balance; this may be sufficient therapy if started early enough, and it may besuccessful adjunctive or maintenance therapy in patients who have required penicillamine. Alter-ations in antioxidant status are important in Wilson’s disease. Dr Fabio Farinati and colleaguesfrom the University of Padua evaluate tissue levels of glutathione and cysteine, as well asmalondialdehyde, in patients with Wilson’s disease under penicillamine or zinc treatment; thesepatients were compared with one another and with patients who had chronic liver disease of anetiology other than Wilson’s disease.

As described beginning on page 372, the investigators obtained liver biopsies from 24 patientswith Wilson’s disease (18 zinc- and 6 penicillamine-treated), 34 patients with chronic viral hepatitis,and 10 patients with alcoholic liver disease. These biopsies were evaluated for their content ofcysteine, reduced/oxidized glutathione, malondialdehyde, zinc, and copper.

In livers from patients with Wilson’s disease, there was less reduced glutathione than there wasin livers from patients with viral hepatitis; the level was similar to that found in levers from patientswith alcoholic liver disease. The cysteine level was also significantly lower than in both controlgroups. The amount of oxidized glutathione (as a percentage of total glutathione) was higher thanin viral or alcoholic diseases. Only those from zinc-treated patients had low malondialdehyde levels.Zinc-treated patients had higher reduced glutathione and lower percentage of oxidized glutathione.As expected, Wilson’s disease patients were found to have changes in glutathione, reducedglutathione, cysteine, and oxidized glutathione, suggesting a milieu favoring excess lipid peroxi-dation. These changes were blunted in patients who were being treated with zinc, and lowermalondialdehyde levels in their livers suggested that the differences were potentially important.Thus, zinc therapy may be not only a gentle way of reducing copper burden; it may also protectagainst oxidant injury.

Oxidative stress and erythropoiesis:Another mechanism for anemia ofchronic disease?

Increased oxidative stress is a common feature of inflammatory disorders, and inflammatorydisorders are those most commonly associated with the “anemia of chronic disease.” It is thereforeinteresting to know whether increased oxidative stress has a direct effect on bone marrow function;this possibility was explored in a tissue culture model by Drs Gail Dallalio and Robert Means ofthe Medical University of South Carolina. In a paper beginning on page 395, they describe theirevaluation of the effects of oxidative stress on erythroid colony formation by bone marrow cells andby progenitor cells derived from the peripheral blood.

When progenitor cells were incubated with hydrogen peroxide (50 �M), erythroid colonyformation was suppressed only if those progenitors had come from the peripheral blood—anobservation that led the authors to suspect a protective role for some other cell in the marrowsamples. The inhibitory effect on growth of peripheral blood-derived colonies was caspase-dependent, suggesting that it might involve alterations in the regulation of apoptosis. Interferons areinflammatory mediators thought to be important in anemia of chronic disease; the authors thereforetested whether an interferon would make the marrow cells behave more like the peripheral bloodcells—that is, to be sensitive to suppression by peroxide. This turned out to be the case. Recom-binant human gamma-IFN, at concentrations which did not inhibit CFU-E colony formation,sensitized LDMN marrow cells to inhibition by H2O2. Thioredoxin may be one of the protectantsinvolved in the relative protection of marrow cells from oxidative stress: when marrow mononuclearcells were incubated with �IFN at high concentrations, the amount of thioredoxin in the supernatant

J Lab Clin Med362 In this Issue June 2003

medium was decreased. The deliberate addition of recombinant thioredoxin, on the other hand,partially reversed the inhibition of colony growth that had been worked by interferon and peroxide.

The authors conclude that inflammatory cytokines implicated in the anemia of chronic diseasemay exert their effects on erythron growth at least in part through modulation of oxidative stress andthe marrow’s defenses against such stress.

Fibronectin and major traumaFibronectin is an important adhesive glycoprotein, a constituent of basement membranes that is

also present in plasma and in the integrity of connective tissue. Fibronectins from different tissuesmay be distinguishable by virtue of alternative splicing; because fibronectin from vascular basementmembrane may be distinct, its measurement in plasma could provide a marker of vascular injury.This idea was tested by Dr John Peters et alii, from the University of California at Davis and severalcollaborating centers.

Using Western blot analysis and ELISA of N-deglycosylated samples, these investigators ob-served that plasma levels of fibronectin bearing the alternatively spliced EIIIB segment (EIIIB� FN)increase in patients following admission to the intensive care unit after major trauma. The level ofthis fibronectin subtype was not elevated in samples taken within 24 hours of ICU admission. Levelsmeasured after the first 24 hours were significantly higher than those found in samples from healthycontrols. After the first few days, levels of EIIIB� fibronectin decreased in the patients’ plasmas;samples taken one month following hospital discharge were indistinguishable from initial samplesor normal samples. These temporal changes are qualitatively quite similar to those encountered forFN isoforms bearing the alternatively spliced EIIIA segment; both EIIIB� and EIIIA� fibronectinmeasurements are quite different from the results obtained when fibronectin is measured nonselec-tively.

The authors conclude that selective measurements of EIIIB� fibronectin can be made in clinicalplasma samples; the specific pattern of results suggests that such measurements may be useful asquantitative markers of vascular injury. Their paper may be found on page 401.

For the editorsDale E. Hammerschmidt, MD

Editor-in-Chief

J Lab Clin MedVolume 141, Number 6 In this Issue 363