KEY WORDS: adenosine deaminase, purine nucleoside phosphorylase, 5'-nucleotidase, carcinogenesis, immune function.The development of a tumor in the body is accompanied as a rule by weakening of the immune response.We now know that lymphoid cells are sensitive to a change in the concentration of products of purine metabolism, and disturbances of immunity in hereditary T-and Bcell deficiency, linked with a disturbance of lymphocyte differentiation and function, are accompanied by reduced activity of some enzymes of purine nucleoside and nucleotide metabolism:adenosinedeaminase (AD), purine nucleoside phosphorylase (PNP), and 5'-nucleotidase. Substantial changes in activity of enzymes of purine metabolism also have been found in the lymphocytes of cancer patients, and the ratio between activities of AD/PNP correlated with the immune status [14], and decreased as the disease progressed.In previous research the writers found considerable deviations in the purine metabolism of thymocytes and the total fraction of splenic lymphocytes of mice and rats with rapidly growing transplanted hepatomas [2, 4]. To determine the role of these disturbances in the pathogenesis of malignant growth, it was necessary to study the biochemical characteristics and immune response of functionally different subpopulations of immunocompetent cells.In the investigation described below activity of AD, PNP, and 5'-nucleotidase and also the DNA content in thymocytes and T-and B-lymphocytes in the spleen of C3HA mice with hepatomas induced by orthoaminoazotoluene (OAAT) were studied.The state of function of the immunocompetent cells was assessed by the blast transformation test (BTT) in response to various mitogens, production of antibody-forming cells (AFC), and also the number of rosetteforming cells (RFC) bearing receptors for the Fc-fragment of immunoglobulin (EA-RFC) and the C'3 component of complement (ECAC-RFC).
EXPERIMENTAL METHODExperiments were carried out on male C3HA mice.A hepatoma was induced with OATT, which was injected subcutaneously in the spinal region monthly in a dose of I0 mg per mouse (in glycerol).All tests were carried out 1 and 3 weeks and 3, 8, and 12 months after the beginning of carcinogenesis.Lymphocytes were isolated from the thymus and spleen in a Ficoll--Verografin gradient [6], after which the splenocytes were passed through a column with nylon wadding to separate them into T and B fractions [i0, 13].Activity of AD and PNP was determined in lysates of lymphocytes, and 5'-nucleotidase activity in intact cells by the method described previously [4]. Activity of the enzymes was expressed in micromoles substrate converted per minute, calculated per 109 cells (units). DNA was determined by the method in [7] and expressed in milligrams per 109 cells.The number of AFC was estimated by the local hemolysis in agar method [ii]. Mice were immunized intraperitoneally with 0.2 ml of a 5% suspension of sheep's red blood cells and the number of AFC in the spleen was counted on the 5th day per 108 nucleated cells.The BTT was car...
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