Identification of a novel 110-kilodalton structure expressed on a subset of T cell receptor-gamma delta-bearing cloned lymphocytes

A small percentage of circulating CD3+ cells express a heterodimeric gamma delta receptor. Most of these cells do not express the surface marker CD4 and only a fraction of them bear CD8 molecules. The specificity and function of TCR-gamma delta are unclear. We obtained a murine mAb produced against an IL-2-dependent human T cell clone defining a novel molecule sTA which is not expressed on resting human peripheral blood CD3+ cells but strongly expressed on a fraction of TCR-gamma delta-bearing clones. Like receptors for growth factors such as IL-2, the sTA Ag is present on clones and cell lines according on the cell cycle. SDS-PAGE analysis of sTA immunoprecipitates from 125I-labeled sTA+ clone lysate demonstrated a single band of molecular mass 110 kDa under reducing conditions. Triggering with anti-sTA mAb did not result in [Ca2+]i mobilization of sTA+ clones. Additionally, the presence of anti-sTA did not alter the cytotoxicity of these sTA+ clones neither against tumor target cells nor against specific PHA blast cells. Interestingly, due to the fact that most sTA+ clones fail to proliferate in response to CD3 triggering, it appears that sTA may serve as a useful marker to study the functional heterogeneity of TCR-gamma delta expressing cells.     

Bleomycin induces cataract formation in newborn rats in association with modifications of crystallin synthesis

The antitumor antibiotic Bleomycin induces the formation of cataract when injected into newborn rats but not when injected into rats after 12 days or older. The development of these lesions is strictly associated with progressive biochemical modifications of the crystallins as demonstrated by electrophoresis on one and two-dimensional gels. When the lenses of the rats are observed histologically, the first modifications appear between 7 and 13 days after the injection of the drug concomitatly with the first biochemical modifications. Lateron the fiber cells start to degenerate and there is a gradual destruction of the whole center of the lens.     

Collective decision-making in white-faced capuchin monkeys

In group-living animals, collective movements are a widespread phenomenon and occur through consensus decision. When one animal proposes a direction for group movement, the others decide to follow or not and hence take part in the decision-making process. This paper examines the temporal spread of individual responses after the departure of a first individual (the initiator) in a semi-free ranging group of white-faced capuchins (Cebus capucinus). We analysed 294 start attempts, 111 succeeding and 183 failing. Using a modelling approach, we have demonstrated that consensus decision-making for group movements is based on two complementary phenomena in this species: firstly, the joining together of group members thanks to a mimetic process; and secondly, a modulation of this phenomenon through the propensity of the initiator to give up (i.e. cancellation rate). This cancellation rate seems to be directly dependent upon the number of followers: the greater this number is, the lower the cancellation rate is seen to be. The coupling between joining and cancellation rates leads to a quorum: when three individuals join the initiator, the group collectively moves. If the initiator abandons the movement, this influences the joining behaviour of the other group members, which in return influences the initiator''s behaviour. This study demonstrates the synergy between the initiator''s behaviour and the self-organized mechanisms underlying group movements.     

Acquisition of object-robbing and object/food-bartering behaviours: a culturally maintained token economy in free-ranging long-tailed macaques

The token exchange paradigm shows that monkeys and great apes are able to use objects as symbolic tools to request specific food rewards. Such studies provide insights into the cognitive underpinnings of economic behaviour in non-human primates. However, the ecological validity of these laboratory-based experimental situations tends to be limited. Our field research aims to address the need for a more ecologically valid primate model of trading systems in humans. Around the Uluwatu Temple in Bali, Indonesia, a large free-ranging population of long-tailed macaques spontaneously and routinely engage in token-mediated bartering interactions with humans. These interactions occur in two phases: after stealing inedible and more or less valuable objects from humans, the macaques appear to use them as tokens, by returning them to humans in exchange for food. Our field observational and experimental data showed (i) age differences in robbing/bartering success, indicative of experiential learning, and (ii) clear behavioural associations between value-based token possession and quantity or quality of food rewards rejected and accepted by subadult and adult monkeys, suggestive of robbing/bartering payoff maximization and economic decision-making. This population-specific, prevalent, cross-generational, learned and socially influenced practice may be the first example of a culturally maintained token economy in free-ranging animals.This article is part of the theme issue ‘Existence and prevalence of economic behaviours among non-human primates''.     

Proliferation of resting lymphocytes is induced by triggering T cells through an epitope common to the three CD18/CD11 leukocyte adhesion molecules.

LFA-1, Mac-1, and p150,95 are a family of functionally important leucocyte integrins that share a common beta-subunit and participate in cellular adhesion. Monoclonal antibody to LFA-1 were described to block T-cell-mediated killing by inhibiting adhesion to target cells and to decrease T cell responses by preventing cell-cell contact. Recently it was demonstrated that LFA-1 molecule was involved in signal transduction. We report here that a monoclonal antibody termed 6.7 reacting with the three members of the leucocyte integrins is able in the presence of monocytes to directly induce the proliferation of resting peripheral blood T cells obtained from normal individuals. These results suggest the possibility that LFA-1 molecules could trigger T lymphocyte activation in addition to their role in homing, growth, and differentiation.     

Inhibition of superoxide production in B lymphocytes by rac antisense oligonucleotides.

Rac1 and Rac2 gene products are small GTP-binding proteins showing 92% homology to each other. According to recent studies performed in cell-free systems, Rac1 and Rac2 proteins may be involved in the activation of NADPH-oxidase, the superoxide-generating enzymatic complex active in phagocytes. Epstein-Barr virus (EBV) transformed B lymphocytes, which express rac1 and rac2 genes, also efficiently release superoxide anions when triggered by various cell surface stimuli. To investigate the regulatory role of Rac proteins in living cells, we analyzed superoxide production in response to cross-linking of surface immunoglobulins or phorbol ester treatment in human EBV-transformed B lymphocytes pretreated with Rac sense and antisense oligonucleotides. We report here that (i) the rac protein content estimated by immunoblotting can be decreased by 60% in Rac antisense pretreated cells and (ii) a strong (50-60%), dose-dependent inhibition of superoxide production is observed in antisense pretreated cells whereas cells pretreated with sense oligonucleotide are unaffected. The data presented show, for the first time in whole cells, that superoxide production is modulated by the Rac protein content, thus demonstrating the physiological role of Rac proteins in the regulation of NADPH-oxidase.     

IL-4 counteracts anti-mu-induced human B cell proliferation: involvement of a cAMP-dependent inhibitory pathway.

In this report we show that IL-4 inhibits DNA synthesis induced by stimulation of human B cells with mitogenic doses of either soluble anti-mu mAb DA44 or phorbol ester. In contrast, earlier steps of anti-mu-induced B cell stimulation, such as RNA synthesis, CD23 expression and IL-6 production, were not inhibited but rather increased in the presence of IL-4. From these results, IL-4 appears therefore to exert two opposite effects on DA44 anti-mu mAb-induced human B cell activation: early steps are stimulated, and later steps inhibited. The results of kinetic analysis were consistent with this model. The inhibitory activity of IL-4 required an active cAMP-dependent pathway since IL-4-mediated inhibition of anti-mu-induced B cell proliferation was abolished in the presence of two specific inhibitors of the cAMP pathway (H8 and 2',5'-dideoxyadenosine which are specific for cAMP-dependent protein kinase and adenylate cyclase respectively). Furthermore, IL-4 induced a delayed and prolonged increase in intracellular cAMP concentrations (observed between 4 and 48 hours of culture), and this strongly suggests that the late inhibitory effects of IL-4 is cAMP-dependent. Moreover, this delayed IL-4-mediated cAMP production is probably sufficient to prevent anti-mu induced DNA synthesis since addition of the cAMP agonist forskolin on day 1 or 2 of culture also suppresses the anti-mu-mediated B cell proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Paf-acether-induced superoxide anion generation in human B cell line

Paf-acether (paf) and lyso phospholipids induced an oxydative burst on EBV-transformed B lymphocyte cell line. Superoxide anion formation measured by lucigenin-dependent chemiluminescence was dependent on both paf concentration and time-course of challenge. Paf C18:0 at 10 microM was more potent than its C16:0 analogue at the same concentration. Choline-containing phospholipids with 2-acyl (long chain) were inactive. The paf antagonists BN 52021 and WEB 2086 structurally unrelated to paf were inactive whereas paf structural analogue CV 3988 inhibited superoxide formation induced by paf and lysophospholipids. Such a phospholipid-induced oxydative burst in B cells might exert an effect in the numerous pathophysiological situations where large amounts of paf are produced by phagocytic cells.