Role of adenosine deaminase in human monocyte differentiation and tumor cell cytotoxicity

Determination of adenosine deaminase activity in cattle naturally infected with Theileria annulata

The purpose of this study was to determine serum ADA activity in cattle naturally infected with Theileria annulata. In this study, a total of 37 cross-bred cattle which 27 of it showing clinical signs of theileriosis constituted infected group and 10 healthy cattle as control group were used as animal materials. Infected group divided into three groups according to their PCV values. Cattle with PCV > or = 25 were put on group I (n = 9), those with PCV 13-24 were put on group II (n = 11) and those with PCV < or = 12 were put on group III (n = 7). Microscopical diagnosis of the disease was also made. Hematological parameters, serum enzyme activities (ADA, AST, ALT and ALP) were determined in all cattle. Hematological results revealed that significant progressive decreases in HGB, PLT, PBML counts and ratios from group I onwards to group III, whereas the WBC, PBPL counts and ratios showed an increase from group I onwards to group III. The serum ADA, AST, ALT and ALP activity increased significantly in all infected groups compared to control group. However, these parameters were also observed to decrease progressively from group I to group III. Furthermore, the highest increase in enzyme activities observed in the infected group I. But, these enzyme's activities started to decrease in infected group II and III in parallel with PBML and PLT counts. Eventhough, this decrease did not reach to the values obtained from control group. On the contrary, PBPL counts and ratios increased in infected group II and III in contrast to decrease in PCV. As a result, increased serum ADA activity in tropical theileriosis may reflect the involvement of the cellular immune responses.

Successful treatment of two children with Langerhans' cell histiocytosis with 2'-deoxycoformycin

PURPOSE

Langerhans' cell histiocytosis (LCH) is problematic illness with a subset of patients experiencing a relapsing or progressive course despite therapy with chemotherapy and/or immunosuppressive agents. Novel therapies are required. 2'-deoxycoformycin (2'-dCF) is an inhibitor of adenosine deaminase (ADA) and is toxic to lymphocytes and monocytes. We hypothesized that 2'-dCF might be effective in treatment of children with LCH, in part because of recent success reported with 2-chlorodeoxyadenosine. In this report we describe our experience using 2'-dCF to treat two patients with refractory LCH.

PATIENTS AND METHODS

The patients, aged 5 and 3 years, had received therapy for 4 and 2.5 years, respectively, with vinblastine, corticosteroids, etoposide, methotrexate, 6-mercaptopurine, and, in one case, cyclosporine. While receiving cyclosporine, the first patient developed rapidly enlarging lytic skull lesions accompanied by pain and tenderness. While receiving methotrexate and 6-mercaptopurine, the second patient developed fever, anemia, multiple new bony lesions, and massive abdominal and axillary adenopathy, proven at biopsy to be due to recurrent LCH. Treatment in both cases was with 2'-dCF 4 mg/m2 given by intravenous push weekly for 8 weeks then continuing every 2 weeks for >21 and 16 months, respectively.

RESULTS

Both patients responded to 2'-dCF therapy. The first patient's pain resolved following three doses of 2'-dCF, and the skull lesions decreased in size significantly over the following 6 months. After 15 months of therapy he developed asymptomatic radiologic evidence of a possible new lesion in the femur which did not progress over the subsequent 3 months. The second patient experienced improvement at all sites of disease over 8 weeks, with complete resolution of bony lesions over the next 5 months. At 16 months from initiation of 2'-dCF therapy she remains disease-free. Toxicity was limited to asymptomatic grade III-IV lymphopenia and abnormalities of lymphocyte mitogen responses. The patients are asymptomatic and continue biweekly and monthly 2'-dCF therapy, respectively.

CONCLUSION

2'-dCF has shown activity against LCH in these two cases, with minimal toxicity. Further study of this agent in the therapy of LCH is warranted.

Potent toxicity of 2-chlorodeoxyadenosine toward human monocytes in vitro and in vivo. A novel approach to immunosuppressive therapy

Lymphoid cells were thought to be uniquely susceptible to excess 2'-deoxyadenosine (dAdo), when exposed to inhibitors of adenosine deaminase (ADA). However, we now find that human monocytes are as sensitive as lymphocytes to dAdo or to the ADA-resistant congener 2-chloro-2'-deoxyadenosine (CldAdo). Monocytes exposed in vitro to CldAdo, or to dAdo plus deoxycoformycin rapidly developed DNA strand breaks. Both the DNA damage and the toxicity of CldAdo or dAdo toward monocytes were blocked by deoxycytidine, but not by inhibitors of poly(ADP-ribose) polymerase. A partial decrease in RNA synthesis and a gradual decline of cellular NAD were early biochemical events associated with monocyte DNA damage. Low CldAdo concentrations (5-20 nM) inhibited monocyte phagocytosis and reduced the release of interleukin 6. Higher CldAdo concentrations led to a dose- and time-dependent loss of monocyte viability. Circulating monocytes disappeared within 1 wk in patients with cutaneous T cell lymphoma or with rheumatoid arthritis during continuous CldAdo infusion. The marked sensitivity of human monocyte function and survival to CldAdo in vitro, together with the monocyte depletion in patients receiving CldAdo chemotherapy, suggests that CldAdo or other dAdo analogues offer a novel therapeutic strategy for chronic inflammatory and autoimmune diseases characterized by inappropriate monocyte deployment or function.