Dichloromethylene diphosphonate (Cl2MDP) reduces natural killer (NK) cell activity in mice.

Daily administration of dichloromethylene diphosphonate (Cl2MDP) to (C57BL/6 X DBA/2) F1 hybrid mice, from two days of age (10 mg of P/kg body weight), resulted in a marked impairment of natural killer (NK) activity of spleen cells against YAC-1 lymphoma cells. The suppressive effect increased with the duration of the treatment. Cessation of the treatment led to a rapid recovery (in 2 weeks) of NK activity while the osteopetrotic bone lesions persisted. Thus, the loss of natural killing cannot be explained by the simple reduction of bone marrow volume secondary to Cl2MDP-induced osteopetrosis. However, as NK cells are considered to be dependent on the bone marrow because they cannot be sustained by extramedullary production, a direct effect of Cl2MDP on the generation of NK cell precursors by the bone marrow was not excluded. Cl2MDP was not directly toxic to the fully differentiated splenic NK cells, since the addition of Cl2MDP to the in vitro assay (10(-5)-10 micrograms/ml) did not reduce cytotoxicity. These studies suggest that impairment of NK activity during Cl2MDP treatment may have clinical toxicologic implications since NK cells have been suggested to play an important role in natural host defenses against infection and neoplasia.

Kinetic studies of the immunopharmacologic effects of NPT 15392 in mice.

NPT 15392 [9-erythro-(2-hydroxy,3-nonyl)-hypoxanthine] was administered in a single intraperitoneal injection to Balb/c mice at a dose of 0.1 mg/kg. Modifications of immune parameters were evaluated 1-14 days after the treatment. NPT 15392 potentiated antibody responses to both T-dependent (SRBC, TNP-KLH) and T-independent (TNP-LPS) antigens and delayed-type hypersensitivity to oxazolone. The proliferative response of spleen cells from NPT-treated mice to stimulation with PHA was depressed, but that to dextran sulphate was augmented. The responses to Con A or LPS were inconsistently modified. NPT 15392 augmented killer cell functions, including both T cell-mediated cytotoxicity against allogeneic tumor cells and NK cell activity against YAC-1 tumor cells. It slightly augmented or depressed ADCC activity against antibody-coated chicken erythrocytes (CRBC) depending on the time of its administration. Concerning the stimulation of NK cell activity, the effect was more marked on spleen effector cells when NPT 15392 was given i.v. and on peritoneal effector cells when it was given i.p. From these results, T helper cells, B cells, and NK cells appeared to be target cells of NPT 15392 action. The various stimulatory effects peaked at different times according to the immune function tested. In addition, the prolonged, sometimes double-peaked action (antibody response to T-dependent antigens, NK activity) indicates complex mechanisms of action which may involve indirect interactions mediated by lymphokines or monokines.

Comparative study of the histologic reactions to intravenous injections of heat-killed Pseudomonas aeruginosa and of BCG.

Intravenous injection (i.v.) of heat-killed Pseudomonas aeruginosa in mice produced histologic changes in the thymic cortex, some of which resembled, while others differed from, those produced by i.v. injection of living BCG. The changes that were similar consisted of pyroninophilia of cortical lymphocytes and hyperplasia of epithelial cells in the medulla and at the corticomedullary junction with increased PAS positive cells and secretions. Major differences, however, in the sequence and nature of the histologic events were observed. Pseudomonas injections produced thymic epithelial cell hyperplasia with increased PAS positive cells and secretions and pyroninophilia of thymic cortical lymphocytes earlier than did i.v. BCG (day 1 versus day 7). Corticomedullary inversion of thymic structure and early transient hyperplasia of the thymus dependent areas in the lymph nodes and spleen occurred after Pseudomonas but not after BCG injections. Hyperplasia in the B cell areas and germinal centers started to appear at day 10 after injection of Pseudomonas and persisted up to day 21 (compared to day 7 and day 14, respectively, for BCG). In contrast to i.v. BCG, Pseudomonas injections did not produce granulomas or macrophage proliferations.

Effects of Bacillus Calmette-Guérin and levamisole on immune responses in young adult and age-immunodepressed mice.

The immunomodulating effects of bacillus Calmette-Guérin (BCG) and levamisole were tested in young adult mice after a single administration and in 12-month-old mice after continuous administration. In young mice, BCG was shown to activate macrophages, to potentiate antibody responses and delayed hypersensitivity reaction, to increase antibody-dependent cell-mediated cytotoxicity, and to induce nonspecific suppressor cells. Levamisole was not able to modify any of these immune responses in young mice. The action of these adjuvants differed markedly when tested in age-immunodepressed mice. BCG was found to be strongly immunosuppressive on antibody formation and induced suppressor cell activity in the spleen. Moreover, the survival of immunodepressed mice continuously treated with BCG was shortened in comparison to untreated aged mice. In contrast, levamisole acted as an immunorestoring agent because it strongly stimulated the antibody response compared to aged controls and did not induce suppressor cell population. The survival of levamisole-treated mice was prolonged when compared to untreated aged mice. When the surviving mice were killed and autopsied at the age of 24 months, the incidence of spontaneous tumors was significantly lower in the group of mice treated by levamisole.

Lymphocyte-macrophage interactions in BCG-treated mice.

Fresh living Bacillus Calmette-Guérin (BCG), injected i.v. into (C57Bl/6xDBA/2)Fl mice, activated peritoneal macrophages rendering them highly cytotoxic for tumor cells in vitro. This cytotoxic activity was already maximal 14 days after injection of 1 mg of BCG and remained stable when 3 or 5 mg of BCG were given. At the same time spleen cells of the BCG-treated mice showed strongly depressed responses to the T-cell mitogens, PHA and Con A, irrespective of the dose of BCG injected. The inhibitory effect was shown to be mediated by suppressor cells which had characteristics of macrophages since they could be removed by carbonyl iron and magnet treatment and were adherent to plastic. In contrast to it was observed after injection of 1 mg of BCG, these suppressor cells alone did not account for the depression of T-cell responses induced by higher doses of BCG. Nylon-nonadherent cell populations obtained from spleen cells treated with 3 or 5 mg BCG partially retained the inhibitory activity suggesting that suppressor T cells were also induced after injection of high doses of BCG.