GVHD pathophysiology: is acute different from chronic?

Graft-versus-host disease (GVHD) is the major complication of allogeneic hematopoietic cell transplantation (HCT). GVHD occurs in acute and chronic forms. Acute GVHD usually manifests within 100 days following HSCT. It is induced by donor T cells responding to the mismatched host polymorphic histocompatibility antigens. Chronic GVHD generally manifests later (>100 days) and has some features of autoimmune diseases. It may develop either de novo or following resolution of - or as an extension of - acute GVHD. Chronic GVHD is also thought to be induced by donor T cells, but the nature of relevant antigens, the critical cellular subsets and the mechanisms of chronic GVHD remain less well understood. In this chapter we briefly discuss and contrast the pathophysiologies of acute and chronic GVHD.

Vascularized lymph node transplantation induces graft-versus-host disease in chimeric hosts.

BACKGROUND: The role of lymph nodes (LNs) in adaptive immune responses has been the subject of extensive research. In previous studies, the surgical removal of lymph nodes from rat hind limbs prevented the development of lethal graft-versus-host disease (GVHD) after allogeneic hind limb transplantation to chimeric recipient rats. The purpose of this study was to establish the role of the cellular fraction versus the microenvironment of LNs in the development of GVHD in this model. METHODS: A rat model for vascularized LN transplantation was developed and graft-versus-host responses were compared after: 1) naive ACI LN cells were infused into Wistar-Furth (WF) rats as chimeric recipients (e.g. [ACI-->WF]); 2) vascularized WF lymph nodes were transplanted to syngeneic WF recipients; 3) nonvascularized ACI lymph nodes were transplanted to [ACI-->WF] chimeric recipients; 4) vascularized ACI lymph nodes were transplanted to [ACI-->WF] chimeric recipients. RESULTS: Transplantation of vascularized ACI lymph nodes to [ACI-->WF] chimeric recipient rats resulted in severe and sometimes lethal GVHD. In contrast, neither the infusion of purified ACI LN cells nor the transplantation of nonvascularized LNs led to GVHD in chimeric recipients. CONCLUSIONS: When introducing allogeneic cells into chimeric recipients, concomitant transplantation of the vascularized LN microenvironment makes a manifest difference between induction and absence of GVHD. This illustrates the important role of the LN microenvironment in adaptive immune responses.

Reappraisal of histologic features of the acute cutaneous graft-versus-host reaction based on an allogeneic rodent model.

We employed a rat model of complete major histocompatibility complex-mismatched allogeneic bone marrow transplantation to better characterize the histologic expression of the acute cutaneous graft-versus-host reaction (GVHR), compared with changes due to the preparative regimen. Cyclosporin A abolished the development of this GVHR. Low levels of dyskeratotic cells were present in all groups (allogeneic and syngeneic transplants with and without cyclosporin A) and, alone, were insufficient to diagnose a cutaneous GVHR. A consistent histologic feature of the GVHR was significant lymphoid infiltration of the dermis. The pattern of cytotoxic folliculitis involved follicular epithelium above the entry of sebaceous glands. Immunostain for major histocompatibility complex class II, IA, and IE antigens revealed that dendritic cells within the follicle were limited to this upper region and that lower follicular epithelium did not upregulate expression with evolution of the GVHR. Based on this model, we conclude 1) that the diagnostic scheme for the acute cutaneous GVHR should include lymphoid infiltration of the dermis, 2) that the preparative regimen (including total body irradiation) induces persistent low levels of dyskeratotic cells (two to three cells/linear mm of epidermis), and 3) that the pattern of follicular involvement may relate to the distribution of dendritic cells and to an inability of lower follicular epithelium to upregulate major histocompatibility complex class II antigens.

Regulatory (suppressor) T cells in peripheral allograft tolerance and graft-versus-host reaction.

Among the mechanisms capable of inducing peripheral tolerance, regulatory (suppressor) T cells (Treg) probably play a key role in the control of both reactivity to self-antigens and alloimmune response. Augmentation or manipulation of Treg could improve organ allograft survival or control graft-versus-host disease, thus resulting in operational tolerance. The role of this immunomanipulation as one method of inducing tolerance has yet to be clearly defined.

Modulation of experimental allergic encephalomyelitis by a host-versus-graft reaction: a clinicopathological study.

The effect of timing of a local host-versus-graft reaction on the induction of acute experimental allergic encephalomyelitis (EAE) was studied in guinea pigs. 20 x 10(7) gamma-irradiated allogeneic cells injected 4 days after encephalitogenic challenge resulted in the development of EAE with an earlier onset, an increased delayed-type hypersensitivity (DTH) response and an increase in lymphoid cell infiltration in the spinal cord. Challenge with allogeneic cells on days -4 and -7, however, produced a delay in onset and a protracted course of disease, with 30-40% of the animals recovering. Evidence of disease was confirmed histologically.

Host-donor interactions in healing of human split-thickness skin grafts onto nude mice: in situ hybridization, immunohistochemical, and histochemical studies.

The behavior of host and donor cell lines in human split-thickness skin grafts onto nude mice was studied by in situ hybridization (ISH) using genomic DNAs as probes, and immunohistochemically with species-specific or cross-species specific antibodies, at different stages ranging from day 3 to more than 1 year following grafting. Changes in the graft vascular and interstitial extracellular matrix were also assessed using species-specific or cross-species specific antibodies to human or murine type I, III, and IV collagens. Finally, transplant reinnervation was investigated using antibodies to various nerve cytoplasmic antigens and the thiocholine method to demonstrate acetylcholinesterase. Using these methods we were able to show the following: (1) the graft epidermis that is not replaced by mouse keratinocytes is progressively colonized by recipient Langerhans cells (LCs); (2) revascularization of the grafts begins soon by inoculation of the graft vessels with the host microcirculatory bed, and mouse endothelial cells growing into preexisting human capillary tubes produce a new basement membrane, prior to the replacement of the original one; (3) within 3-5 days following grafting, mouse fibroblasts migrate into the graft dermis. The density of the human and murine fibroblast populations then progressively increases. Characterization of the interstitial collagens identifies both human and murine type I and III collagens. Production of type III collagens decreases during the progression of fibrogenesis while human type I collagen becomes the predominant matrix protein; (4) transplant reinnervation is deficient, and neurites growing into severed graft nerve trunks were never detected.

Specific immunosuppression by postoperative infusion of allogeneic spleen cells: requirement of donor major histocompatibility complex expression and graft-versus-host reactivity.

BACKGROUND: Donor leukocytes may exert positive immunoregulatory effects on allograft acceptance. Most recent studies have focused on pretreatment protocols. In this study, the effect of postoperative infusion of donor leukocytes on graft survival and the phenotypic and functional requirements for infused cells were investigated in fully major histocompatibility complex (MHC)-mismatched rat heart transplant models. METHODS: LEW (RT1l) heart grafts were implanted heterotopically into abdomens of LEW.1W (RT1u), and different types of cells were infused postoperatively. Immunohistochemistry was used to evaluate histopathological changes of grafts. RESULTS: In the absence of any immunosuppressive agents, a single dose of viable donor spleen cells (SC), but not bone marrow cells, was able to prolong heart allograft survival to about 21 days, while they were rejected promptly at day 7 in controls. Infusion of T cell-depleted donor SC, irradiated donor SC or third-party (BN) SC showed no effect on graft survival. Compared with resting cells, neither in vitro nor in vivo prestimulation of infused donor SC improved graft survival. Clinical signs of graft-versus-host reaction were not observed in all above groups. Histology showed remarkable reduction in the severity of graft infiltrate and interleukin-2 receptor-positive cells in grafts of cell-treated animals. Postoperative infusion of SC of F1 generation between different strain combinations showed two requirements for infused cells to be effective: (1) expression of donor-type MHC antigens and (2) strong alloreactivity against the host MHC antigens. CONCLUSION: Postoperative infusion of viable donor SC can lead to allospecific down-regulation of alloreactivity by a graft-versus-host-associated effect.

Evidence for a graft-versus-mast-cell effect after allogeneic bone marrow transplantation.

Mast cell leukemia (MCL) is a rare form of aggressive mastocytosis with a reported median survival below 6 months. Casuistic reports suggest the effectiveness of allogeneic bone marrow transplantation (BMT) for MCL. However, these reports lack clear evidence for a graft-versus-mast-cell (GvMC) effect. We prospectively investigated the GvMC at different time points after allogeneic BMT and donor-lymphocyte infusions (DLI). Samples were gathered from a patient with MCL treated with allogeneic BMT from an unrelated HLA identical donor. Parameters for detection of a GvMC effect included flow cytometrical analysis of mast cell (MC) populations in peripheral blood and BM, BM smear and histology, chimerism analysis of flow cytometrically sorted BM CD117+/CD34- MC and testing for anti-mast cell reactivity of donor lymphocytes by interferon (IFN)-gamma ELISPOT. DLIs reduced MC from 5 to 0.5%. MC chimerism analysis demonstrated a complete recipient genotype after BMT, suggesting that the persistent mastocytosis was part of residual neoplastic disease. At 3.7 years after BMT, there is some evidence for relapse. In summary, BMT and DLIs attenuated the mastocytosis from an aggressive to an indolent form and may have improved the patients' prognosis. The in vitro data of our study indicate for the first time the existence of a GvMC effect.

Biology of acute and chronic graft-versus-host reactions: predictive value of studies in experimental animals.

Experimental research on graft-versus-host disease (GVHD) with laboratory animals has been performed mainly with rodents, rhesus monkeys and dogs. The basic immunological mechanisms operative in GVHD are largely similar in these three species and in human patients, although the patterns of GVHD in the three animal species show differences. The predictive value for clinical GVHD of the results obtained in the different animals species is analysed for the three main variables: namely, histocompatibility, T cell numbers in the graft and the intestinal microflora. Rhesus monkeys score highest as regards clinical relevance for the first two variables. With regards to the unravelling of detailed mechanisms of the influence of the microflora, none of the three animal species is likely to provide the information needed for identification of the bacterial species involved in the induction of GVHD in human patients.

The influence of graft-versus-host reactivity, lymphocyte depletion, and cell dose on allogeneic bone marrow engraftment.

Graft rejection has hampered the use of T cell depletion (TCD) in allogeneic bone marrow transplantation. A model of host-versus-graft (HVGR) and graft-versus-host reaction (GVHR) as two inversely related processes has been proposed. We investigated graft rejection rates in graft-versus-host-reactive and graft-versus-host-nonreactive situations in a rat and a mouse model. Model 1: LEW rats were pretreated with a fixed myeloablative dose of busulfan and increasing doses of the immunosuppressive cyclophosphamide. The animals received different doses of semiallogeneic GvH-nonreactive BM cells. Graft rejection rates were dependent on the bone marrow cell number transplanted and on the pretransplant immunosuppression. Graft rejection rates following transplantation of GvH-reactive CAP marrow and genetically GvH-nonreactive (CAP x LEW)F1 marrow were the same. In conclusion, there was no advantage with respect to engraftment for the GvH-reactive marrow. Model 2: In irradiated Balb/c mice, graft rejection rates following T cell-depleted and unmanipulated transplantation of GvH-reactive or GvH-nonreactive bone marrow grafts were identical. All experiments were done with graded numbers of BM cells and revealed a strong impact of the BM cell dose on engraftment. In our experiments the cell loss during the ex-vivo manipulation was approximately 50% and, in contrast to the clinical situation, we readjusted to the intended number after TCD. Our experiments demonstrate that neither GvHR nor T cells but the BM cell dose has a strong impact on engraftment of allogeneic bone marrow.

Low levels of eicosapentaenoic and docosahexaenoic acids mimic the effects of fish oil upon rat lymphocytes.

Fish oil is rich in the long chain n-3 polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); typically these fatty acids constitute 20 to 25 g/100 g total fatty acids in fish oil. Feeding rodents diets rich in fish oil has been shown to decrease lymphocyte proliferation and natural killer cell activity. It is not known what level of EPA + DHA is required in the diet to exert these effects. This question was addressed in the current study. Weanling rats were fed on high fat (178 g/kg) diets which contained 4.4 g alpha-linolenic acid (control) or 4.4 g EPA + DHA (4.4 EPA + DHA) or 6.6 g EPA + DHA (6.6 EPA + DHA)/100 g total fatty acids. The n-6 to n-3 polyunsaturated fatty acid ratio was maintained at approximately 7. The fatty acid compositions of the serum and of spleen leukocytes were markedly influenced by that of the diet. Spleen lymphocyte proliferation in response to concanavalin A, spleen natural killer cell activity and PGE2 production by spleen leukocytes were reduced by feeding the EPA + DHA diets compared with feeding the control diet; the 4.4 and 6.6 EPA + DHA diets caused very similar reductions. The 4.4 EPA + DHA diet reduced popliteal lymph node weight following a localised graft versus host response; this response was not investigated in rats fed the 6.6 EPA + DHA diet. The reductions in lymphocyte functions and in the in vivo graft versus host response caused by the EPA + DHA diets were similar to those previously reported following the feeding of diets rich in fish oil. Thus, this study shows that diets containing relatively low levels of EPA + DHA (20 to 25% of the level found in fish oil) exert immunomodulatory effects. Furthermore, this study suggests that the maximal effect of EPA + DHA is exerted when these fatty acids constitute a level of less than or equal to 4.4 g/100 g total dietary fatty acids.

Age-related changes in graft-versus-host reactivity of spleen cells from male, virgin, or multiparous female Long-Evans rats.

Spleen cell graft-versus-host (GVH) reactivity was determined in male and female, either virgin or breeder, Long-Evans (LE) rats from 3 to 24 months of age. The tests of a regional (popliteal lymph node enlargement index) and a systemic (splenomegaly index, mortality assay) GVH reaction was used. Although the GVH reactivity declined with age in both sexes, the onset of this decline was significantly delayed in 18-month-old virgin females in comparison with 12-month-old males. Moreover, 6 or 7 consecutive pregnancies resulted in significantly enhanced GVH reactivity of 18-24-month-old females. This long-lasting effect of multiparity was observed in females mated either syngeneically or allogeneically. The possible role of neuroendocrine factors in delaying the age-related process of thymic involution in multiparous females is suggested.

Effects of the chromatographic fractions of the pig placental trophoblast on graft-versus-host reaction.

The trophoblast has a significant role in regulation of immune reactions at the materno-fetal interface by producing biologically active substances. In our previous studies five fractions with immunomodulatory activities were isolated by gel chromatography from trophoblast of pig placentas. To confirm the immunomodulatory effect of these trophoblast fractions on allogeneic in vivo systems and to obtain more evidence for the relevance of their activity on the maternofetal interface, their effect was studied on graft-versus-host reaction (GVHR). To assess the GVHR, the primary and secondary popliteal lymph nodes assay was used in mice. In the primary GVHR, 100 microg protein of Fraction 2-5, mixed with 5 x 10(6) allogeneic spleen cells (C57BL/6), were injected into one of the foot pads of recipient (BALB/c) mice. The secondary GVHR was induced in F1 (BALB/c x C57BL/6) mice by injection of spleen cells of BALB/c mice intraperitoneally preimmunized with allogeneic cells. The GVHR was measured by the weight of lymph nodes and by the lymphocyte proliferation. Flow cytometric analyses of the cells in the nodes with GVHR and under the influence of Fraction 4 or 5 were performed using monoclonal antibodies. In the primary GVHR, Fraction 4 or 5, injected simultaneously with allogeneic spleen cells, significantly suppressed the lymph nodes reactivity. Fractions 4 and 5 inhibited the ability of the spleen cells of mice intraperitoneally preimmunized with allogeneic cells to induce secondary GVHR in F1 mice. The Fraction 2 and 3 had no effect on GVHR. The results revealed that a group of proteins with Mr 37-7 kDa, isolated from trophoblast of pig placenta, strongly suppressed popliteal lymph node reactivity in the primary and secondary GVHR. The data provide convincing evidence for these fractions in vivo activity, for their effect across the species barrier and suggest the relevance of the same reactions on the materno-fetal interface.

[Immunodeficiency caused by graft versus host reaction. Extra-thymic effect of thymus in restoring immunity]. / Déficit immunitaire lié à la réaction du greffon contre l'hôte. Influence extra-thymique du thymus dans la restauration de l'immunité.

Cell-mediated immunity in lethally irradiated graft-versus-host mice can be restored after repopulation with syngeneic bone marrow cells and thymus grafting. The thymus is not only required for the maturation of T lymphocytes, but also for the inhibition of a radioresistant mechanism resulting in lymphoid cell rejection.

Donor-recipient gender difference affects severity of dry eye after hematopoietic stem cell transplantation.

PURPOSE: To determine whether the incidence rate and severity of dry eye after hematopoietic stem cell transplantation varies with donor vs recipient gender. METHODS: We limited this study to patients received bone marrow transplantation (BMT). In all, 172 patients received BMT at Keio University School of Medicine between January 2000 and May 2007. Of them, 136 recipients who survived at least 70 days were studied prospectively. We classified the 136 patients according to the gender of the donor and the recipient (group I: female to female; group II: male to male; group III: male to female; group IV: female to male). The incidence and severity of chronic graft-vs-host disease-associated dry eye were determined for each group. The donor gender was masked when we assessed dry eye and calculate the incidence. RESULTS: The incidence of dry eye was 47.4% for group I, 37.5% for group II, 58.6% for group III, and 42.9% for group IV. The percentage of patients with severe dry eye was 44.4, 50.0, 35.3, and 77.8% respectively. There was a significant difference between the percent severe dry eye/total dry eye incidences in groups III and IV (P=0.0375) (odds ratio, 7.6; 95% confidence interval, 1.00-101.01). CONCLUSIONS: Close attention must be paid to the development of dry eye in cases of female to male BMTs, because the ratio of severe/total dry eye is more common in cases of female to male BMTs than in other gender combination.