Down-modulation of lymphoproliferation and interferon-gamma production by beta-glucan derived from Saccharomyces cerevisiae

Beta-glucan, one of the major cell wall components of Saccharomyces cerevisiae, has been found to enhance immune functions. This study investigated in vivo and in vitro effects of beta-glucan on lymphoproliferation and interferon-gamma (IFN-gamma) production by splenic cells from C57BL/6 female mice. All experiments were performed with particulate beta-glucan derived from S. cerevisiae. Data demonstrated that both, i.p administration of particulate beta-glucan (20 or 100 µg/animal) and in vitro stimulation of splenic cells (20 or 100 µg/ml of culture) decreased lymphoproliferation and IFN-gamma production induced by concanavalin A. These results suggest that beta-glucan can trigger a down-modulatory effect regulating a deleterious immune system hyperactivity in the presence of a strong stimulus.

Absence of seasonal effect on the immunomodulatory action of brazilian propolis on natural killer activity

Propolis, a beehive product widely used in folk medicine as an antiinflammatory agent, has been attracting researchers attention to scientifically elucidate its biological properties and therapeutic activities. The aim of this paper was to study the possible effect of propolis on natural killer activity, since propolis immunomodulatory action has been suggested, especially on non-specific immunity. Propolis was produced by africanized honeybees (Apis mellifera L.), collected throughout a whole year, and pooled by season. Hydroalcoholic solutions of propolis were prepared with each pool and administered to rats by gavage over three days. Natural killer activity of non-adherent spleen cells was evaluated by the 51Cr-release cytotoxicity assay against Yac-1 target cells. Our results indicated that the natural killer activity was increased in spleen cells from propolis-treated animals. There were no significant differences related to the seasonal effect on the immunomodulatory action of propolis.

Use of an ELISA assay to evaluate venom, antivenom, IgG and IgM human antibody levels in serum and cerebrospinal fluid from patients bitten by Crotalus durissus terrificus in Brazil

A sandwich-type ELISA technique for specific and sensitive detection of Crotalus durissus terrificus venom antigens, horse-antivenom, human IgG and IgM antibodies was set up. Sixteen patients, 13 males and 3 females aged between 13 to 63 years (mean 33 ñ 15) bitten by Crotalus durissus terrificus snakes were studied. Of the 15 patiens, 6 had previously received anti-Crotalus venom and no seric venom was detected. For the other 9 patients studied, the venom levels ranged from 2 to 108mg/ml according to the severity of each case. Seric antivenom was detected up to 44 days after the bite. IgM human antibody levels against Crotalus venom were higher between 3 and 18 days after specific treatment. IgG human antibody levels against Crotalus venom were detected between 30 and 90 days after envenoming. Venom and antivenom levels in cerebrospinal fluid were not observed 24 h after the bite. This suggests that neither the venom nor the antivenom is capable of crossing the blood-brain barrier. In addition, when either venom or the antivenom is presented to the immune system cells an immune response is prepared.

Inhibitory effects of cimetidine on graft survival of allotransplanted rats submitted to an active-passive enhancement protocol

The objetive of the presented study was to determine wheter cimetidine, a type-2 histamine receptor antagonist, inhibits the immunological enhancement of allografted rats achieved by treatment with donor antigen plus anti-donor antibody. Groups of rats submitted to this active-passive enhancement protocol and treated ip with 30 (APEC30; Group I; N = 4) or 60 (APEC 60; Group II; N = 8) mg/day cimetidine for 14 days had a significantly shorter graft survival (20.2 ñ 5.1 and 11.1 ñ 2.6 days, respectively) than the control group (animals submitted to the enhancement protocol and killed on day 72 after transplant when the graft was beating normally; APE; Group III; N = 6; P<0.05). On the other hand, these animals had a significantly longer graft survival than rats allotransplanted but not treated for enhancement (ALLO; Group V; N = 5; 8.2 ñ 0.8 days). The surgical control, consisting of isotransplanted animals, had a long-term survival (ISO; Group V; N = 6; rats killed 120 days after transplant with the graft beating normally). Animals treated with cimetidine, but not submitted to the enhancement protocol (AC 60; Group IV, N = 4) had a significantly shorter graft survival (6.25 ñ 0.5) than the allotransplanted animals (Group V). These results indicate inhibition of the suppressor mechanisms which participate in this type of immunological enhancement

Immunomodulatory effect of cimetidine on the proliferative responses of splenocytes from T. cruzi-infected rats

O efeito imunomodulatorio da Cimetidine (CIM), um antagonista do receptor de histamina-tipo 2, foi avaliado na resposta blastogenica a Con A em celulas de ratos Wistar Furth (WF) infectados pela cepa Y de Trypanosoma cruzi (T.cruzi). Foi observado que apenas na concentracao de "10 POT. -3"M de Cimetidine houve amplificacao da resposta blastogenica de esplenocitos normais a Con A. Entretanto, a capacidade mitogenica de esplenocitos de animais infectados foi restaurada na presenca de molaridades da droga que variaram entre "10 POT. -8" a "10 POT. -3". Os resultados demonstraram que a CIM tem o potencial de modular a resposta mitogenica de celulas de animais infectados pelo T.cruzi, sugerindo um papel imunoregulatorio da histamina e/ou celulas que expressam receptores H2 nesta infeccao.