G Hale

ELIMINATION OF GRAFT-VERSUS-HOST DISEASE BY IN-VITRO DEPLETION OF ALLOREACTIVE LYMPHOCYTES WITH A MONOCLONAL RAT ANTI-HUMAN LYMPHOCYTE ANTIBODY (CAMPATH-1)

A new monoclonal rat anti-human lymphocyte antibody (CAMPATH-1) which lyses cells with autologous human complement was used for depletion of T lymphocytes from human bone-marrow allografts in vitro before transplantation in 11 high-risk patients. HLA-matched siblings were used as marrow donors. T-cell depletion was substantial when measured by E-rosette formation (0-0.18% residual T cells) and immunofluorescence with a monoclonal anti-T-cell antibody (0-0.5%). No anti-graft-versus-host disease prophylaxis was given after transplantation. Rapid engraftment was reported in all patients, and the post-transplantation course was uneventful. No signs of graft-versus-host disease developed in any of the patients, who were observed for a maximum period of 12 months. The method might be suitable for larger-scale studies in high-risk patients. The late graft failure seen in 2 patients may reflect residual host resistance uncompromised by GvHD.

T-cell-depleted allogeneic bone marrow transplantation for acute leukaemia using Campath-1 antibodies and post-transplant administration of donor's peripheral blood lymphocytes for prevention of relapse

One hundred and forty‐six patients with acute leukaemia (81 with ANLL and 65 with ALL) received allogeneic bone marrow transplantation from their fully matched siblings. 121 patients underwent T‐cell depletion (TCD) using Campath 1 monoclonal rat anti‐human lymphocyte (CDw52) antibodies; 67 with Campath 1M and 54 with Campath 1G isotypes. Patients were conditioned for transplant using either total body irradiation combined with chemotherapy (125 patients) or busulfan and cyclophosphamide (21 patients). 112 recipients of T‐cell depleted allografts received in addition total lymphoid irradiation (TLI) for prevention of rejection. Engraftment of neutrophils (>0.5 × 109/l) and platelets (>25 × 109/l) occurred on days 15 and 18, and on days 18 and 20 in recipients of Campath 1M and Campath 1G treated marrows respectively. Rejection was documented in 6.8% of T‐cell depleted transplants. Leukaemia relapse‐free survival at 2 years was 83% for patients transplanted in first CR, 76% in second CR (P2= 0.34) and 42% in advanced leukaemia (P2= 0.009). 81 marrow recipients, 38 with Campath 1M and 43 with Campath 1G treated marrow, received post‐transplant graded increments of donors peripheral blood lymphocytes (PBL) to induce graft‐versus‐leukaemia (GVL) effects. Administration of donors PBL was associated with clinically significant GVHD and with decreased relapse rate especially in patients with ALL. Our data suggest that in patients receiving marrow allografts depleted of T cells by Campath 1 monoclonal antibodies, rejection can be reduced by adequate pregrafting immunosuppression. In patients with advanced disease, post‐transplant cell‐mediated immunotherapy (CMI) using donors PBL may be beneficial; however, further studies are needed to define the optimal schedule of CMI for safe and effective prevention of relapse following TCD bone marrow transplantation in malignant haematological diseases.

Effect of graft perfusion with two CD45 monoclonal antibodies on incidence of kidney allograft rejection.

In a blind trial, 77 patients were randomised to receive first cadaver kidney allografts that had been perfused either with a pair of CD45 monoclonal antibodies (mAbs), in an attempt to reduce the immunogenicity of passenger leucocytes, or with control human albumin solution. No complications of mAb perfusion were observed. Patient and allograft survival were similar in both groups. Rejection episodes were recorded in 7 (18%) of the patient with mAb perfused allografts compared with 24 (63%) of the controls.

Monoclonal antibody therapy of chronic intraocular inflammation using Campath-1H.

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Excessive T cell depletion of peripheral blood stem cells has an adverse effect upon outcome following allogeneic stem cell transplantation

We evaluated the outcome of two modes of T cell depletion for HLA-identical sibling stem cell transplants in 34 consecutive adult patients: group A (n = 11) received PBSC post CliniMACs immuno-magnetic enrichment of CD34+ cells and group B (n = 23) received bone marrow following in vitro incubation with CAMPATH-1M and complement. All patients received an identical conditioning regimen which consisted of in vivoCAMPATH-1H 20 mg over 5 days, thiotepa 10 mg/kg, cyclophosphamide 120 mg/kg and 14.4 Gy TBI. No additional graft-versus-host disease prophylaxis was given. The mean T cell dose administered was 0.02 ± 0.05 × 106/kg for group A and 2.8 ± 2.8 106/kg for group B (P < 0.001). With a median follow-up of 28 months overall survival was 36.4% for group A at 12 months compared to 78.3% for group B (P = 0.001). Transplant-related mortality in group A at 12 months was 63.6% as compared to 18.0% in group B (P = 0.003). Most of the procedure-related deaths in group A occurred secondary to infection. These results suggest that extensive in vitro T cell depletion of peripheral blood stem cells in combination with in vivo T cell depletion may have profound effects upon the incidence of infections following allogeneic stem cell transplantation and this may adversely effect transplant-related mortality. Bone Marrow Transplantation (2001) 28, 827–834.

Rat monoclonal antibodies for bone marrow transplantation--the CAMPATH series.

Successful allogeneic marrow grafting requires that T-cell mediated responses of both donor and recipient be prevented (Korngold and Sprent, 1978; van Bekkum, 1984). Marrow transplantation is unique in the sense that there is an interplay between Graft versus Host (GvHD) and Host versus Graft (HvG) processes. Subclinical GvHD probably contributes to the immunosuppression which guarantees stem cell engraftment. The corollary of this is that success at purging T cells from donor marrow risks the prospect of marrow rejection by the recipient (see van Bekkum, 1984; Vallera et al, 1982; Vriesendorp et al, 198lab Miller et al, 1983, Wagemaker et al, 1981).

Therapeutic potential of monoclonal antibodies to the leucocyte common antigen.

The leucocyte common (LC) antigen is a major glycoprotein family of leucocyte membranes. Monoclonal antibodies against the rat, mouse and human antigens have been described (Sunderland et al., 1979; Trowbridge, 1978; Dalchau et al., 1980). Its cell distribution and molecular weight are very similar in the three species. It is widely distributed on leucocytes, being found on T and B lymphocytes, thymocytes, macrophages and granulocytes, but is absent from other tissues. Its apparent molecular weight by SDS-PAGE is about 200 kilodaltons, but up to four species with slightly different mobilities have been observed according to the cell type studied (Dalchau and Fabre, 1981; Banga et al., 1984).