The role of T-cell depletion of autografts for autoimmune diseases

Series Editor: P. Woo

M. Bierings

University Hospital `Het Wilhelmina Kinderziekenhuis', Department of Haematology–Bone Marrow Transplantation, PO Box 18009, 3501 CA Utrecht, The Netherlands

Chemo-radiotherapy can lead to severe damage of the bone marrow and may lead to myelo-ablation. In order to overcome this toxicity, autologous haematopoietic stem cells can be infused. These stem cells can be either bone marrow derived or harvested from peripheral blood using leucapheresis. An unmanipulated bone marrow or peripheral blood autologous graft will contain considerable amounts of autologous T cells. With the infusion of the autologous stem cells, these T cells will be reintroduced into the patient.

Why consider T-cell depletion?

T cells might include autoreactive cells, responsible for autoimmune symptoms. Hence, re-infusion of autologous T cells may prevent the elimination of autoreactive T-cell clones. In 1996, Euler et al. [1] reported the early recurrence or persistence of autoimmune diseases after unmanipulated autologous stem cell transplantation. He described five patients. The majority of these patients were primarily autografted for malignancies, all but one with peripheral blood stem cells. The T-cell content of these autografts was, as can be expected, high: 27–423x106 /kg CD3+ cells. The conditioning regimens used differed widely, only one patient's treatment included (6x2 Gy) total body irradiation (TBI). In these patients, autografting failed to induce more than transient remission of autoimmune diseases. The autoimmune diseases were highly variable.

There are several explanations for the failure to control autoimmune disease in these patients. Either the conditioning was not the appropriate treatment for the autoimmune disease, leading to insufficient immunosuppression, or the unmanipulated graft contained autoreactive T cells that were re-infused. It is also possible that the autoimmune disease is an inherent defect of the autologous haematopoietic stem cells and that resetting the `immunostat' by eliminating autoreactive T cells does not prevent the autoimmunity from recurring.

In order to investigate the value of T-cell depletion of the autograft, several techniques can be employed. T cells can be eliminated either by antibody depletion of T cells themselves (negative selection) or by positively selecting the haematopoietic (CD34+) stem cells and reinfusing these selected stem cells. These techniques can be combined for higher efficiency. Various techniques and devices are currently used to achieve this goal. They will be discussed in detail by I. C. M. Slaper-Cortenbach in this issue.

Clinical experience so far

In the EBMT/EULAR Autoimmune Disease Stem Cell Project, 40 patients treated with autografts have been reported between 1994 and 1997 [2]. Diagnoses included multiple sclerosis, systemic sclerosis, systemic lupus erythematosus, amyotrophic lateral sclerosis, idiopathic thrombocytopenic purpura (ITP), pure red cell aplasia and autoimmune haemolytic anaemia. In this series of 40 patients, T-cell depletion was performed in 19 patients. In 13 grafts, CD34-positive selection was employed; in six, both positive CD34 selection and B- and T-cell elimination were used. No outcome results of this series have been published yet. Published results for autografts in autoimmune diseases are limited.

In chronic idiopathic thrombocytopenia, conflicting anecdotal reports have been published. Lim et al. [3] reported two refractory chronic thrombocytopenia patients who were autografted with peripheral blood stem cells, mobilized using oral cyclophosphamide and filgrastim. Conditioning consisted of cyclophosphamide, cumulative dose 200 mg/kg. The grafts were not manipulated. Both patients went into complete remission, with follow-ups at 7 and 11 months. The T-cell content of the graft is not described in this publication. Skoda et al. [4] reported a patient with chronic idiopathic thrombocytopenia who was autografted with T-cell-depleted peripheral blood stem cells who did not respond to this treatment. Conditioning in this patient was similar to the regimen used by Lim and co-workers. The T-cell content of the graft employed by Skoda was 1.9x105 /kg after positive and negative selection with Ceprate A and antibodies, respectively. The anecdotal results of Lim and Skoda do not enable an evaluation of the role of T-cell depletion for autografts in refractory chronic ITP.

In multiple sclerosis, the existing data also make it hard to draw conclusions. In his first series, Fassas et al. [5] treated 15 patients with progressive multiple sclerosis with unmanipulated peripheral blood stem cells after a BEAM conditoning regimen. However, in these cases, anti-thymocyte globulin (ATG) was administered on days +1 and +2 (after infusing the autograft), leading to an in vivo T-cell depletion. The level of T-cell depletion in these cases cannot be determined.

In Fassas' series, the results were encouraging: durable neurological improvements have been detected in two disease-severity scoring systems in the vast majority of patients.

Burt et al. [6] recently reported three patients with multiple sclerosis who were autografted with T-cell-depleted (CD34+ selected cells) combined bone marrow and peripheral blood stem cells. The median T-cell doses administered were rather high: 8x105 /kg. Conditioning consisted of cyclophosphamide (120 mg/kg), TBI (eight fractions of 150 cGy) and methylprednisolone. Outcome measurement was primarily by MRI and showed at least stable disease.

In rheumatoid diseases, the data are also scarce. Joske [7] autografted an adult patient with erosive, seropositive and polyarticular rheumatoid arthritis, refractory to various treatments, including methotrexate and cyclosporin. Mobilization was with cyclophosphamide (4 g/m2 ) and granulocyte-colony stimulating factor. Upon neutrophil recovery, there was a disease flare-up. Conditioning was with cyclophosphamide (200 mg/kg cumulative dose) and dexamethasone (8 mg/day). The graft was not T-cell depleted. There was a clear improvement in the patient's condition after the procedure, although at 6 months follow-up he was still on 9 mg prednisolone daily.

Wulffraat et al. [8] autografted four children with severe systemic and polyarticular juvenile chronic arthritis, with a T-cell-depleted bone marrow graft. T-cell depletion was with anti-T-lymphocyte monoclonal antibodies, the mean T-cell dose was 0.3–0.5x105 /kg. Conditioning consisted of cyclophosphamide (200 mg/kg cumulative dose) and a single fraction of 4 Gy TBI. In addition, ATG was administered on days -9 to -5. In all patients treated so far, there was a clear improvement in disease activity.

In conclusion, the experience so far is in a limited number of patients with highly variable diseases, stem cell sources, graft manipulations and conditioning regimens. Hence, no conclusions can be drawn at this point in time. This also emphasizes the urgent need to limit the number of different protocols in use to enable the medical community to gain meaningful data on how to treat autoimmune diseases with autografts.

To what level should T cells be depleted?

Experimental data reported by Kernan et al. [9] show that allografted patients who received <105 T cells/kg body weight develop no graft-versus-host disease (GvHD), whereas four of seven patients who received between 1.0x105 and 4.4x105 T cells/kg developed grade I–II skin GvHD. Since GvHD can be considered the clinical result of donor-reactive graft-derived T cells, a safety limit of 1.0x105 T cells/kg can be defined. This level of T-cell depletion is feasible by current techniques.

T-cell depletion, at what cost?

There are two main disadvantages to T-cell depletion. The first is the risk of delayed full immune reconstitution, although limited data are available yet. Secondly, it is a costly procedure: the costs per processed graft range from $2500 to $5000, depending on the technique(s) used.

Concluding remarks

In theory, there are good reasons to eliminate T cells in autografts for autoimmune diseases. With current techniques, it is possible to infuse <105 T cells/kg body weight, a safety threshold for the elimination of autoreactive clones from the graft based on experimental data. It is, at present, not possible to judge the clinical benefit of T-cell depletion of autografts for autoimmune diseases, based on clinical experience.

In order to evaluate the effectiveness of these procedures, it is urgently necessary to limit the number of autograft protocols used.

References

  1. Euler HH, Marmont AM, Bacigalupo A, Fastenrath S, Dreger P, Hoffknecht M et al. Early recurrence or persistence of autoimmune diseases after unmanipulated autologous stem cell transplantation. Blood 1996;88:3621–5.[Abstract/Free Full Text]
  2. Passweg J, Fassas A, Furst D, Black C, Finke J, Jouet J et al. Autologous stem cell transplantation for autoimmune disease: a preliminary report. Bone Marrow Transplant 1998;21:S51(Abstract).
  3. Lim S, Kell J, Al-Sabah A, Bashi W, Bailey-Wood R. Peripheral blood stem-cell transplantation for refractory autoimmune thrombocytopenic purpura. Lancet 1997; 349:475.[ISI][Medline]
  4. Skoda RC, Tichell A, Tyndall A, Hoffman T, Gillessen S, Gratwohl A. Autologous peripheral stem cell transplantation in a patient with chronic autoimmune thrombocytopenia. Br J Haematol 1997;99:56–7.[ISI][Medline]
  5. Fassas A, Anagostopoulos A, Kazis A, Kapinas A, Sakellari I, Kimiskidis V et al. Peripheral blood stem cell transplantation in the treatment of progressive multiple sclerosis: first results of a pilot study. Bone Marrow Transplant 1997;20:631–8.[ISI][Medline]
  6. Burt RK, Traynor AE, Cohen B, Karlin KH, Davis FA, Stefoski D et al. T-cell depleted autologous hematopoietic stem cell transplantation of multiple sclerosis: report on the first three patients. Bone Marrow Transplant 1998;21: 537–41.[ISI][Medline]
  7. Joske DJL. Autologous bone-marrow transplantation for rheumatoid arthritis. [Letter] Lancet 1997;350:337–8.[ISI][Medline]
  8. Wulffraat NM, van Royen A, Vossen JP, Kuis W. Autologous bone marrow transplantation in refractory polyarticular and sytemic JCA. Bone Marrow Transplant 1998;21:S50 (Abstract).[Medline]
  9. Kernan N, Collins NH, Juliano L, Cartagena T, Dupont B, O'Reilly RJ. Clonable T lymphocytes in T cell-depleted bone marrow transplants correlate with development of Graft-versus-Host disease. Blood 1986;68:770–3.[Abstract]
Accepted 15 March 1999