Early effect of Mycobacterium tuberculosis infection on Mac-1 and ICAM-1 expression on mouse peritoneal macrophages

Effect of M. tuberculosis infection was studied on the expression of intercellular adhesion molocule-1 (ICAM-1) and Mac-1 markers on murine peritoneal macrophages. Intraperitoneal administration of M. tuberculosis resulted in a marked increase in the proportion of Mac-1+ cells whereas the proportion of ICAM-1+ cells declined sharply 4 h post infection. Absolute numbers of Mac-1+ and ICAM-1+ cells however increased at all time points after the infection. Comparison of kinetics of changes observed in Mac-1+ and ICAM-1+ cell populations with differential leukocyte counts in peritoneal cells indicated that these alterations could be due to cellular influx, especially that of neutrophils, or up regulation of these markers on macrophages and other peritoneal cells. In adherent peritoneal macrophages infected in vitro with M. tuberculosis, proportion of Mac-1+ and ICAM-1+ cells increased markedly within 24 h of infection. Mean expression of these markers on per cell basis also increased significantly. Similar results were obtained by using RAW 264.7 mouse macrophage cell line, suggesting that the enhanced expression of Mac-1 and ICAM-1 markers was a direct effect of M. tuberculosis infection and not mediated by contaminating cell types present in adherent macrophage preparations. Mac- 1 and ICAM-1 expression was further studied on macrophages that had actually engulfed M. tuberculosis and compared with bystander macrophages without intracellular M. tuberculosis. For this purpose M. tuberculosis pre-stained with DilC18 fluorescent dye were used for infecting adherent peritoneal macrophages. Mac-1 and ICAM-1 expression on gated DilC18 positive and negative cell populations was analyzed. Our results indicate that the expression of Mac-1 and ICAM- 1 markers was significantly enhanced on all macrophages incubated with M. tuberculosis but was more pronounced on macrophages with internalized mycobacteria. Taken together, our results suggest that the expression of Mac-1 and ICAM-1 markers is significantly up regulated

Cytolytic activity of mitogen activated old and young mouse spleen cells against tumor target cells expressing high or low levels of Fas antigen

Sensitivity of Fas expressing tumor cells (high levels in Hut78 & Jurkat; low levels in P815) toward the cytotoxic Con-A (5 microg/ml) activated spleen cells from young (12 to 16 week old males) and old (2 year old males) mice were studied. The spleen cells from young mice activated for a day showed high levels of cytotoxic activity against Hut78 and Jurkat cell lines but not against P815 cells. The cytotoxic activity against P815 cells were detected in the spleen cells from old but not young mice following a longer period of Con-A activation (three days). Comparable levels of cytotoxic activity against Hut78 and Jurkat cells were observed in the spleen cells from both young and old mice following three days of activation. Treatment of Hut78 cells with anti-Fas antibody affected the tumor cells become resistant against the cytotoxic activity of the spleen cells from young mice in a dose dependent manner however P815 cells were not affect by the anti-Fas antibody treatment. These results show that there are differences in the sensitivity of target tumor cells toward Con-A induced cytotoxic spleen cells from young and old mouse. Mitogen-induced cytotoxic lymphocytes from young mouse spleen appear to kill targets through mechanisms involving Fas antigen, specially, in early stage (1 day) of activation. Old mouse spleen cells generated high levels of cytotoxic cells in later phase (3 days), which appear to kill through Fas-unrelated mechanisms.

Clipboard.

Motivation for specific tasks derives significantly from environmental feedback. For instance, if performance of an action results in immediate sensation of pain, I am likely to avoid repeating it; however, if the action results in pleasurable feedback, I will look for an opportunity to do it again. Thus, one learns through trial and error to perform actions that are positively reinforced and avoid those which result in negative reinforcement. The cognitive and even cellular bases for these psychological phenomena have begun to be unravelled by combining psychological studies with positron emission tomography (PET), functional magnetic resonance imaging (fMRI), electrophysiology, and biological chemistry. Rats may be trained to repeat complex actions, such as traversing a maze or operating a lever, if the performance of this action results in a food reward. In ] 954, aids and Milner announced that the food reward could be effectively substituted by electrical stimulation of specific regions of the brain; in fact, the rats would learn to stimulate themselves. In ensuing years, the basal forebrain as well as some other brain regions have been identified not only as part of a brain-stimulation reward pathway, but also as the pathway activated by natural reward. The natural reward system involves many regions of the brain and many neurotransmitter systems. However, a substantia! role is played by the dopaminergic mesocorticolimbic pathway which impinges on the basal forebrain. More simply put, neurons that secrete or respond to the transmitter dopamine, playa very important role in the sensation of reward, which critically underlies the reinforcement of particular behaviours. Food, success, and sex activate dopaminergic transmission in the !?;r!.al forebrain and behaviours directed towards these comme>dities are normally reinforced in the brain. Thus, healthy animals (those selected for in the wild) are motivated to achieve social and sexual success. A subset of animals in any species, for instance rogue lions and chimpanzees among non-human animals, or saints, scholars, and cocaine addicts in human society, do not play by the same rules as others. Behaviours that stimulate their reward pathways are presumably different in some way. This has been demonstrated recently by fMRI scanning studies on cocaine addicts where brain activities were measured itl vivo during the anticipation, rush, high, and low phases that occur at different stages of cocaine reception (Breiter et at 1997). Cocaine, which blocks the re-uptake of dopamine following its release, prolongs dopaminergic transmission in parts of the brain that constitute the reward pathway. Thus, by directly activating an acute sensation of reward, cocaine seeking behaviour is very strongly reinforced. It is probably not a coincidence that it is those with fewer rewards from "normal life" that are more frequently attracted to an easy pharmacological solution. The sensitivity of the reward pathway to different environments is also influenced by genetic rather than epigenetic phenomena (Rocha et at ] 998). Like all mammalian systems, the brain shows a remarkable tendency towards homeostasis. For this reason, chronic use of cocaine probably results in adaptation of the reward system, such that the "set point" for hedonism (intense sensation of reward) is altered. The reduced sensitivity of this adapted reward system may now increase craving for cocaine stimulation (for a more rigorous and detailed review read Koob and Moal 1997). While reward-seeking is a major source of motivation, fear, the desire to avoid negative reinforcement in the form of pain, is also a strong source of motivation. Like the sensation of reward, fear may be induced in rats by direct electrical stimulation of a specific anatomical region of the brain-the central nucleus of the amygdala. In classical conditioning experiments, a conditioned stimulus such as a high pitched tone can be associated with a negative (unconditioned) stimulus such as electric shocks applied to the feet of a rat (footshock). Recent studies have shown that while a tone produces only a small response in the amygdala of an untrained rat, it produces a greatly enhanced response in the amygdalar.

Missing self by heterogeneous natural killer cells.

Some murine (YAC, P815 and SP20) and human (Molt4, Raji and HR7) tumour cell lines were (i) treated with IFN-γ for inducing enhanced expression of MHC class I antigen, or (ii) given a brief treatment with citrate buffer (pH 3.0), which resulted in denaturation of class I MHC antigens on these tumour cells. IFL-γ or acid treated tumour cells were used as unlabelled competing targets in cold target inhibition assays. The results indicated that the competing ability of acid-treated tumour cells remained unaltered, whereas IFN-γ treated tumour cells competed with significantly less efficiency. These results have been evaluated in light of the current view of NK cell development and the expression of inhibitory receptors for MHC class I molecules (IRMs), on NK cells. A modified view on NK cell heterogeneity based upon IRM expression has been proposed which reconciles several apparently discordant observations about the activity and role of NK cells. Two classes of NK cells have been proposed. Type I NK ceils have target recognition receptors which do not recognize autologous normal cells, lack IRMs, and may participate in first line of defence against transformed cells in vivo. Type II NK cells have target recognition receptors for autologous normal cells and express at least one selfreactive IRM in order to prevent auto-killing. Type II NK cells participate in killing those transformed cells which down-regulate their MHC class I expression in order to escape cytotoxic T-cell surveillance. It is also postulated that mechanism of inverse correlation of target cell MHC class I expression levels and their susceptibility to NK cells, involves interference model of missing self hypothesis for type I NK cells and inhibitory signal model of missing self hypothesis for type II NE cells. Finally, it is proposed that acid treatment of tumour cells enhances their lysis susceptibility by making them additionally susceptible to type II NK cells, rather than enhancing their killing by type I NK cells. This proposition would explain the lack of effect of acid treatment on the competing ability of tumour cells, when target cells are only lysed by type I NE cells.

Species specificity of a novel factor which augments the expression of MHC class I antigens on tumor cell lines

A novel factor which augments the expression of major histocompatibility complex I (MHC augmenting factor or MHC-AF) antigens on tumor cell lines, has been isolated from the culture supernatants of human peripheral blood mononuclear cells activated by concanavalin-A. A mouse equivalent of this factor has also been isolated from the culture supernatants of mouse spleen cells activated by mitogens or in a mixed lymphocyte reaction. Mouse MHC-AF enhances the expression of class I MHC antigens on murine tumor cell lines (EL-4 and BW5147) but not on human tumor cell lines (K562 and HR-7). Human MHC-AF on the other hand enhances the MHC I expression on both human as well as murine cell lines. Interferon gamma (IFN-gamma), a cytokine also known to enhance the expression of MHC I antigens, acts in a highly species specific manner with mouse IFN-gamma augmenting the MHC I on murine tumor cell lines and human IFN-gamma augmenting the MHC I on human tumor cell lines only. These results indicate important differences in the cross species biological activities of MHC-AF and IFN-gamma, and provide additional evidence for MHC-AF being distinct from IFN-gamma.