Redefining 'self': the role of microflora (commensals) mismatch in the development of GvHD after allogeneic stem cell transplantation and some possible remedies

The discovery of human leukocyte antigen (HLA) molecules and their role in allorecognition has facilitated the initiation of allogeneic stem cell transplantation in human beings. HLA mismatch to a large extent explains the phenomenon of graft rejection and graft versus host disease (GvHD). Incidence of GvHD even in syngeneic transplants suggests a role for extra genetic factors in the causation of GvHD. We hereby propose a hypothesis that the definition of 'self' (in the immunological sense) should be broadened to include both genetically determined molecules (e.g. HLA) and the microbial flora that colonize an individual. This hypothesis explains several observations about GvHD which can not fully be accounted for by the HLA mismatch theory and gives some clues towards circumventing GvHD.

Autologous bone marrow/stem cell transplantation: initial experience at a north Indian referral centre

BACKGROUND

High-dose chemotherapy and/or radiation therapy rescued by autologous bone marrow or peripheral blood stem cells is being increasingly used for the treatment of haematological and solid malignancies. While few centres in India use this modality of therapy, the worldwide experience is encouraging. We, therefore, analysed the results of our initial experience with this therapeutic modality.

METHODS

Forty-two patients [multiple myeloma (17), Hodgkin's disease (4), non-Hodgkin's lymphoma (3), chronic myeloid leukaemia (2), acute myeloid leukaemia (2), acute lymphoblastic leukaemia (2), epithelial ovarian cancer (6), breast cancer (4), primitive neuroectodermal tumour and testicular germ cell tumour (1 each)] underwent high-dose chemotherapy followed by either autologous bone marrow transplant (n = 9), peripheral blood stem cell transplant (n = 30) or both (n = 3). The indications for transplant included either advanced stage at diagnosis, other adverse prognostic indicators during the course of their disease, or relapse. The data were analysed retrospectively in December 1998 using hospital records. Follow up data of all the patients were available.

RESULTS

Thirty-four of the 42 patients (81%) showed stable engraftment. Eight patients (19%) died in the early post-transplant period (day 5 to day 52 post-transplant). Seven patients died due to neutropenic infections and one due to acute renal failure. Of the 34 surviving patients, 20 were alive at the time of analysis and 14 had died. All but one death in this group were due to progressive primary malignancy. The median overall survival for all patients was 17 months and for the 34 engrafted patients it was 27 months. An analysis of factors affecting survival revealed that patients with chemosensitive disease had a longer overall survival (20.9 v. 6.1 months, p = 0.04) compared to those with chemoresistant disease.

CONCLUSION

Autologous bone marrow or peripheral stem cell transplantation is a feasible procedure in India with an acceptable morbidity and mortality. It should be offered more frequently to properly selected patients.

Blood stem cell transplantation: current concepts

Mobilized peripheral blood haematopoietic progenitor cells are increasingly being used as against bone marrow (BM) transplants, following high dose chemotherapy and/or radiotherapy for the management of chemosensitive malignancies. Rapid haematopoietic reconstitution as evidenced by reduced duration of neutropaenia, fewer donor platelet infusions, shorter hospital stay and reduced cost of treatment are the advantages of this procedure. Reduced tumour cell contamination of mobilized blood compared to bone marrow however, has not been substantiated. Mobilization of lymphokine activated killer cells (LAK), use of blood stem cells (BSC) for allogeneic transplants and ex vivo expansion of the mobilized cells are emerging as the future areas for research. Addition of interleukin-3 (IL-3), stem cell factor (c-kit ligand) and PIXY-321 appear to open-up new vistas by enforcing trilineage and multilineage haematopoietic reconstitution.

Storage of haemopoietic stem cells for autologous bone marrow transplantation

For reinfusing autologous bone marrow cells after high-dose chemotherapy and/or radiotherapy it is necessary that an effective technique for their storage is available. The traditional method uses 10% dimethyl sulphoxide as cryoprotectant, a rate-controlled computerized freezer programmed to cool the cells at a constant rate of 1 degrees C per minute and liquid nitrogen as the storage system. The method is time-consuming, expensive and requires technical expertise. Moreover, it is often associated with varying levels of clinical toxicity following infusion of the preserved cells. Processing the harvest to reduce the initial volume and the mature cells has been shown to be beneficial in reducing the volume of the cryoprotectant and the incidence of toxicity. An alternative, cost-effective method using a cryoprotectant mixture of 5% dimethyl sulphoxide, 6% hydroxyethyl starch and 4% albumin has been found to be effective even when the cells are stored at -80 degrees C without rate-controlled freezing. However, its efficacy needs to be evaluated for extended periods. The current use of purging and cell sorting methods seems to be promising.

Orbital granulocytic sarcomas (myeloid sarcomas) in acute nonlymphocytic leukemia

In a series of 89 patients with acute leukemia, orbital granulocytic sarcomas were observed in 7. All these patients had acute nonlymphocytic leukemia, and they were all children. The orbital involvement usually was bilateral, and the patients had proptosis, conjunctival hemorrhage, and chemosis. Morphologic, cytochemical, and immunophenotypic analyses did not show a predilection for any particular myeloid cell type. Two patients had biphenotypic leukemias with myeloid components. The ocular manifestations responded well to chemotherapy irrespective of the hematologic response.