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Biomedical subjects

L Varesio

Publications and source records attributed to L Varesio.

At least 127 records · Page 7Linked to original sources
PubMed1981

Activation of murine macrophages. I. Different pattern of activation by poly I:C than by lymphokine or LPS.

The ability of poly I:C to activate mouse macrophages (M phi) to become tumoricidal was evaluated and compared with the ability of 2 other agents, lipopolysaccharide (LPS) and M phi-activating factor (MAF), to induce a tumoricidal state. All these agents were able to stimulate proteose-peptone-elicited M phi to kill RL male 1 tumor cells in an 18-hr 51Cr release cytotoxicity assay. High levels of cytotoxicity were obtained with concentrations as low as 1 microgram/ml of LPS or poly I:C and with 1/81 dilution of MAF. However, in the presence of reagents shown to contain less than 0.01 ng/ml of LPS by the LAL assay (LPS free), we found that poly I:C induced strong reactivity, whereas MAF was ineffective. The addition of 10 ng/ml of LPS during the stimulation period did not enhance the cytotoxicity induced by poly I:C, but it did restore MAF-induced, M phi-mediated cytotoxicity. In addition, poly I:C induced strong tumoricidal activity in resident M phi and in peritoneal exudate cells from the genetically defective C3H/HeJ mice that normally do not respond to LPS and MAF treatment. Therefore, it seems that although LPS is required as a second signal for MAF-induced cytotoxicity, such a second signal is not required for poly I:C-induced cytotoxicity. From the above results, it appears that poly I:C is a more powerful activating agent than LPS and MAF and either activates M phi via a different pathway or is effective on subpopulations of M phi that are not activated by the other agents.

Animals↗
PubMed1980

Suppression of T-cell mediated lymphokine production but not cytotoxic activity by macrophages.

We directly compared the effects of macrophages from infiltrating MSV-induced regressing tumors (T-M0) or from the peritoneal cavity of mice previously injected with light mineral oil (LMO-M0) on two functions of alloimmune spleen cells (ISC), the cytotoxic activity and production of a lymphokine, macrophage inhibitory factor (MIF). Addition of T-M0 or LMO-M0 to ISC did not inhibit their cytotoxicity. In contrast, T-M0, but not LMO-M0, mixed with ISC inhibited their ability to produce MIF. We propose that the differential sensitivity of the two immune functions to the macrophage-dependent suppressor activity is due to the ability to M0 to inhibit lymphocyte protein synthesis, with MIF production, but not T cell killing, requiring active protein synthesis.

Animals↗
PubMed1980

A microsystem to evaluate the synthesis of [3H]leucine labeled proteins by macrophages.

A method is described for evaluating protein synthesis by adherent M phi by measuring the incorporation of [3H]leucine into TCA precipitable material. By using guanidine-HCl it was possible to remove completely the radiolabeled proteins from the adherent cells that were cultured in microwells, and retain TCA precipitable material. This procedure enabled us to harvest the TCA precipitable proteins with a semiautomatic cell harvester. The guanidine-HCl treatment did not affect the recovery of the radioactive proteins and did not alter the sensitivity of the assay. This method is very simple and rapid and, since it is suitable for processing microcultures, permits detailed studies on the biology of small numbers of M phi.

Amino Acids↗
PubMed1980

Endotoxin requirement for macrophage activation by lymphokines in a rapid microcytotoxicity assay.

A short term microcytotoxicity assay is described for studying the activation of M0 by lymphokines. Proteose-peptone-induced macrophages were purified by adherence in flat-bottomed microtiter plates and then activated by MAF-containing supernatants for 18 h. 51Cr-labeled tumor target cells were added for an additional 18 h, and then the supernatants were harvested and the % isotope release quantitated. When endotoxin-free medium and FBS were used, we found that small amounts of LPS were absolutely required for macrophage activation in this assay. The advantages of this technique included (a) good reproducibility, (b) the requirement for small number of M0, and (c) the potential of standardizing the assay and thereby testing a large number of samples. Moreover, this assay may have particular value for investigations of M0 activation by exogenous stimuli, since M0 that were not pretreated with activating agents did not exhibit cytotoxicity.

Animals↗
PubMed1980

Mechanism of lymphocyte activation. II. Requirements for macromolecular synthesis in the production of lymphokines.

Reversible inhibitors of protein synthesis, cycloheximide and puromycin, and an irreversible inhibitor of RNA synthesis, actinomycin D, were employed to study the kinetics and types of macromolecular synthetic events required for the production of migration inhibitory factor (MIF) and macrophage activating factor (MAF) by Con A-stimulated lymphocytes. Reversible inhibition of protein synthesis during the first 2 hr of stimulation completely inhibited MIF and MAF production. The same treatment, performed 4 hr after the beginning of the stimulation, had no effect. When the inhibitors of protein synthesis were left in the cultures, a block of lymphokine production was observed when the drugs were added at 6 hr as well as at time 0. In contrast, irreversible inhibition of RNA synthesis at 6 hr was ineffective and only treatment at the beginning of culture blocked lymphokine production. These data suggest that a critical protein is synthesized during the first few hours of stimulation, which is required for subsequent production of lymphokines. After this special early requirement, however, continued protein synthesis is needed for lymphokine production. In contrast, the RNA required for MIF and MAF production seemed to be completely synthesized within 4 to 6 hr of stimulation. The possibility that suppressor macrophages inhibit lymphokine production via modulation of macromolecular synthesis is discussed.

Animals↗
PubMed1980

Regulation of lymphocyte activation: macrophage-dependent suppression of T lymphocyte protein synthesis.

We investigated the influence of macrophages on lymphocyte protein synthesis in C57Bl/6N mice. When activated macrophages recovered from MSV-induced regressing tumors or peritoneal macrophages induced by C. parvum injection were cultured for 6 hr with resting or Concanavalin A-stimulated normal spleen cells, a decrease of protein synthesis was observed. In contrast, peritoneal macrophages induced by injection of light mineral oil or a macrophage cell line, WEHI-3, were completely ineffective. When the mixed cultures of normal spleen cells and macrophages were fractionated, we found that Thy 1.2-positive, nylon-nonadherent cells, but not plastic adherent cells, had a depressed protein synthesis. The suppressor cells, on the contrary, were Thy 1.2 negative, adherent, and phagocytic. We concluded that activated macrophages are able to inhibit T cell protein synthesis. In comparative studies, we found that the macrophage-dependent suppression of protein synthesis correlated with the capacity of the macrophage to suppress production of a lymphokine, migration inhibitory factor, by in vitro stimulated lymphocytes. The possibility that an early block of protein synthesis is one mechanism through which suppressor macrophages inhibit the immune response is discussed.

Animals↗
PubMed1980

Mechanisms of lymphocyte activation: linkage between early protein synthesis and late lymphocyte proliferation.

An experimental model has been developed to study the mechanisms of lymphocyte activation. Using this model we examined the relationship between early protein synthetic events and the late proliferative response to Con A. We found that transient puromycin or cycloheximide-induced inhibition of protein synthesis during the first hour of stimulation by Con A resulted in either inhibition or enhancement of the response, depending on the subsequent treatment of the cells. If the lymphocytes were either not restimulated or restimulated immediately after the initial pulse with metabolic inhibitor plus Con A, there was a decrease in the proliferative response. However, if the cells were restimulated with Con A 24 hr later, there was a shift in the kinetics resulting in a prolonged and increased response. Inhibition of protein synthesis at 6 hr after stimulation with Con A produced no noticeable effects. Hence, there are protein synthetic events that take place during the first hours of stimulation that are critical for the development of the proliferative response. The possibility that these early protein synthetic events are the target for macrophage-mediated regulation of lymphocyte function is discussed.

Animals↗
PubMed1979

Suppression of lymphokine production by macrophages infiltrating murine virus-induced tumors.

Immune spleen cells from mice injected with murine sarcoma virus (MSV) can produce migration inhibition factor (MIF) in vitro after stimulation with intact tumor cells. We have now found that this effector function can be regulated by suppressor macrophages present in the tumor. The cells from the tumor (CfT) exert a strong suppressive effect even after treatment with anti-Thy 1.2 plus complement but lose this capacity if adherent or phagocytic cells are removed, suggesting that the macrophage is the suppressor cell. The effects of the suppressor cells were exerted on a proliferation-independent function of the lymphocytes, since MIF production, as well as its suppression, occurred even after proliferation of the lymphocytes was blocked by mitomycin-C. The implications of these findings are that macrophages can suppress some early events involved in the activation of lymphocytes by antigen and that they do so through a mechanism that does not relate to the proliferation of the cells.

Animals↗
PubMed1979

Functional heterogeneity and T cell-dependent activation of macrophages from murine sarcoma virus (MSV)-induced tumors.

In studies on the functional activity of macrophages isolated from murine sarcoma virus (MSV)-induced tumors, we have found that these cells may suppress immune responses as well as act as effector cells against the tumor. Previously, we reported that macrophages from the tumor could inhibit the antitumor response by suppressing proliferation-dependent immune functions. Here, we demonstrate that macrophages can also suppress the production of migration inhibition factor (MIF) and macrophage activation factor (MAF), two lymphocyte activities that are independent of cell proliferation. Conversely, we and others have found that macrophages from the tumor can exert an antitumor, cytolytic effect. In this study, using 1 g velocity sedimentation separation techniques, we have been able to identify 2-3 subpopulations of cytolytic macrophages in regressing tumors but in progressing tumors, only the smallest subpopulation of macrophages was active. T cells appeared to be required for activation of macrophages within the tumor, since MSV tumors induced in athymic, nude mice did not contain cytolytic macrophages.

Animals↗
PubMed1978

Kinetics of antibody response in unprimed recipients after transfer of immune lymphocytes.

Spleen cells from mice immunized with SRBC were transferred, at various times after immunization, to non-irradiated and lethally irradiated syngeneic recipients. The PFC kinetics and anti-SRBC antibody titres were followed in various groups of mice. Similar results were obtained both in non-irradiated and lethally irradiated recipients, showing that after the transfer: a) PFC proliferation was blocked, b) PFC blocking was unrelated to their maturation stage, c) resting PFC were still able to synthesize antibodies, d) blocking activity was radio-resistant.

Animals↗