ATG antithymocyte globulin

Nonspecific immunosuppressive therapy in an adult patient is usually through cyclosporin (35), started intravenously at the time of transplantation, and given orally once feeding is tolerated. Typically, methylprednisone is started also at the time of transplantation, then reduced to a maintenance dose. A athioprine (31) may also be used in conjunction with the prednisone to achieve adequate immunosuppression. Whereas the objective of immunosuppression is to protect the transplant, general or excessive immunosuppression may lead to undesirable compHcations, eg, opportunistic infections and potential malignancies. These adverse effects could be avoided if selective immunosuppression could be achieved. Suspected rejection episodes are treated with intravenous corticosteroids. Steroid-resistant rejection may be treated with monoclonal antibodies (78,79) such as Muromonab-CD3, specific for the T3-receptor on human T-ceUs. Alternatively, antithymocyte globulin (ATG) may be used against both B- and T-ceUs. 

Both globulins exert their effect by depletion of circulating lymphocytes either by complement-dependent lysis or by phagocytosis after opsonization. However, antilymphocyte globulin (ALG) and antithymocyte globulin (ATG) are nonhuman polyclonal antibodies. To prevent sensitization application is restricted to a time period of several days only. 

The final chapter comprises two reports on clinical haematopoietic stem cell transplantation (HSCT). Viktor Khomenko shares the experience of the Kiev center for stem cell transplantation. The final article in this book by Axel Zander and colleagues summarises data with the use of Antithymocyte globuline (ATG) in (HLA-mismatched) allogeneic transplantation, an approach which was promoted in the Hamburg Clinic for HSCT. 

Antisera directed against lymphocytes have been prepared sporadically for over 100 years. With the advent of human organ transplantation as a therapeutic option, heterologous antilymphocyte globulin (ALG) took on new importance. ALG and antithymocyte globulin (ATG) are now in clinical use in many medical centers, especially in transplantation programs. The antiserum is usually obtained by immunization of large animals such as horses or sheep with human lymphoid cells. 

The antithymocyte globulin (ATG) Fresenius S, produced in rabbits, is an example of a polyclonal antibody mixture used in immunosuppressive therapy in combination with other immunosuppressive agents (e.g., cyclosporine, prednisone) after organ transplantation. 

Immunosuppression is used in patients who are not candidates for bone marrow transplantation due to age or to the lack of a donor (up to 70%). Horse antithymocyte globulin (ATG) or rabbit antilymphocyte globulin (ALG) induce haematological responses (transfusion-independence and freedom from infection) in 40-50%. The addition of ciclosporin to ATG or ALG improves response rates to 70-80% and survival rates in responders to 90%. Adverse effects of ATG and ALG include anaphylaxis, exacerbation of cytopenias and serum sickness. Ciclosporin is nephrotoxic. In refractory patients G-CSF and erythropoetin can improve blood counts, as can androgens in some patients. 

Antithymocyte globulin (ATG) has been used to treat WG refractory to other agents. In one study, three of four patients with severe orbital WG responded to rabbit ATG (2 partial, 1 complete) (197). In an open-label study, 15 patients with active refractory WG were treated with ATG (198). The patients had received a mean of 5.2 different therapies without control of disease. Favorable responses to... 

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