The role of a parasite-produced or -induced soluble immunosuppressor in experimental kala azar was examined. It was found that in vivo infections with Leishmania donovani in the hamster (Mesocricetus auratus) produce a soluble immunosuppressor, which appears in the serum of the host and which reduces the proliferation of responding populations of murine splenocytes in a one-way mixed leukocyte reaction (MLR). The production in vitro infections of murine splenic macrophages from C57BL/6J ($Lsh sp{ rm s}$), C57L/J ($Lsh sp{ rm R}$) and BALB/c strains, the suppressive activity was not contained in either parasite-conditioned culture medium or in parasite extracts or from macrophages which have internalized killed parasites or inert particles and it is not blocked by the action of 2-mercaptoethanol or indomethacin in the culture medium. The suppressor was found to be able to selectively inhibit or reduce the proliferation of splenocytes of both the C57BL/6J and C57LN strains in a one way MLR, with the level of suppression being significantly greater upon splenocytes of the susceptible $Lsh sp{ rm s}$ strain. The suppression was dependent upon the genotype of the macrophages present in the responding population. The suppressor was also able to significantly inhibit the processing of human serum albumin by macrophages, to reduce the number of Ia ligands on the surfaces of macrophages and the production by these cells of IL-1 upon silica stimulation. / Significant reduction was also seen in the production of IL2 and in the expression of its receptor by PHA-stimulated T cells exposed to the suppressor. Partial purification and identification of the suppressor demonstrated that the suppressive activity was present in fractions between 30 and 50 kDa in size; the suppressor was also heat labile and freeze-thaw sensitive. The suppressive molecule(s) may therefore play a significant role in the establishment and pathology of L. donovani infections.

In this study, we determined the immunogenicity of CWP2 and its potential as a vaccine candidate against giardiasis. CWP2 was expressed as a recombinant protein with an hexa-histidine affinity tag and was isolated from inclusion bodies. When BALB/c mice were immunized with CWP2, a specific IgA was detected in the feces. When mice were immunized with CWP2 + cholera toxin, as an adjuvant, IgA in the feces, and IgA, IgG1, and IgG2a in the serum, all specific to CWP2, were detected. Also, CD-1 mice were infected with G. muris and presence of specific IgA antibodies to CWP2 were detected in the feces. This result indicated that CWP2 was recognized by the immune system in a natural infection. IL-4 and IL-5 were released from Peyer's patches (PP) and mesenteric lymph nodes (MLN) cells when stimulated with concanavalin A. In spleen cells, IFN-gamma, IL-4, and IL-5 were released when stimulated with concanavalin A. However, in PP, MLN and spleen cells, the levels of cytokines were barely detectable when stimulated with CWP2. The presence of IgG2a (Th1), IgA and IgG1 (Th2) as the production of IFN-gamma (Th1), IL-4 and IL-5 (Th2) confirmed that CWP2, when presented orally to mice, stimulates both a Th1 and Th2 type immune response, locally and systemically.

Malaria is one of the most serious human infectious diseases. To date, the collection of studies suggest that the disease is determined by transmission dynamics and host age altogether with host genetics and immunological responses. The precise and direct contribution of parasite components to the activation of such immunological responses has not been fully unravelled. In addition to a role proposed for plasmodial GPI, different lines of evidence suggest that hemozoin (HZ) could also be a potential inflammatory agent. The role of HZ in the modulation of immune responses has remained a polemic subject, making it difficult to describe the contribution of this molecule in pathogenesis of malaria. However, our previous laboratory studies, suggest that HZ has a pro-inflammatory role. For this reason, our study was designed to further define the contribution of HZ to the pro-inflammatory events related to malaria immunopathology, and to identify the intracellular signals underlying the up-regulatory effects of HZ in the macrophage, one of the major sources of inflammatory mediators in malaria. In order to do that, we used a chemically characterized synthetic version of the native PfHZ, rcHZ; and evaluated its effects on macrophage nitric oxide (NO) production. Our first approach was to compare the effects of rcHZ with other morphologically different versions of this molecule (aHZ and scHZ) alone or in combination with IFN-gamma on macrophage NO production. In a second approach, we evaluated if the presence of serum proteins plays a role in the increased IFN-gamma induced-NO production by rcHZ. In the third part of our study, we explored if rcHZ is able to increase NO production by macrophages when incubated in combination with a molecule from another pathogen, such as gram-negative bacteria lipopolysaccaride (LPS). The present study is a functional study that uses a synthetic and morphologically identical version of the native PfHZ. Our results suggests that intrinsic physical characteristics, such as shape and size; presence of host serum proteins, and presence of other pathogenic molecules, are important determinants for the macrophage response to HZ in the context of NO production. Besides, it describes part of the signaling pathways that are involved, which may contribute in the future, not only to understand mechanisms of regulation; but also, to find new therapeutic targets against malaria.

No description available.

Prostaglandin E2, postulated to be immunosuppressive to the tumor bearing host, is produced and excreted in elevated quantities by many tumors. Arachidonic acid, the precursor molecule for PGE2, is released from membrane phospholipids by phospholipase A2. Phospholipase A2 has been proposed as the rate limiting enzyme in the production of prostaglandin E2.Phospholipase A2 from different sources varies in substrate specificities, pH optima, and Ca ++ concentration requirements. Therefore, the determination of its specific activity depends on the development of appropriate incubation, extraction, and identification methodologies.This study attempted to develop methodologies for determination of PLA2 activity using enzymes from snake venom, mouse liver, and normal and tumored mouse mammarytissue. The method of substrate preparation, kind of substrate, amount of protein, length of incubation, and addition of KC1 and deoxycholate were varied. Reaction products were extracted and isolated with hexame, and methylated with diazomethane. The methyl esters were identified by gas liquid chromatography. Quantitative analyses were based on proportionality of experimental peak areas to internal standard peak area.Activity could not be demonstrated with snake venom or liver PLA2 preparations. Low specific activity was obtained in some tumor and normal mammary tissue extracts. These studies will be used as a basis for developing an optimal assay system for PLA2 from normal and tumored mouse mammary tissue.

Antibiotic usage is on the rise in industrialized countries and as a result the prevalence of autoimmune and atopic diseases has risen. The use of antibiotics is connected to a depletion of the microflora located within the gastrointestinal tract. The microflora contains a variety of different bacterial species, including some that are probiotic species, Lactobacilli and Bifidobacteria, which have a beneficial effect on the host. Probiotic species of bacteria are important for immune function due to their ability to regulate oral tolerance, a state of unresponsiveness to antigens that have been introduced orally to the host. The goal of this study was to assess the effect of broad spectrum antibiotic treatment on the probiotic species Lactobacilli and the resulting effect on the induction of oral tolerization to the antigen ovalbumin. / Department of Biology

Access to abstract restricted until May 2014 / Access to thesis restricted until May 2014 / Department of Biology

No description available.

No description available.

Biological and immunological aspects of the host-parasite relationship were examined in mice which are susceptible (A/J) and resistant (B10.A) to Giardia muris. B10.A exhibited a shorter latent period, lower cyst output during the acute phase of the infection and shorter period of cyst release compared to A/J. Characteristics of the infection transmitted from mouse-to-mouse and those induced by oral inoculation with cysts or trophozoites were similar. The infection was longer in male A/J and B10.A mice compared to females. Susceptibility and resistance during both the acute and elimination phases of the infection were under non-H-2-linked multigenic control. A/J and B10.A differed in non-specific serum IgG and IgA, but not in the specific IgG and IgA to G. muris. Specific antibodies participated in complement-mediated killing of trophozoites. Spleen, mesenteric lymph node and peritoneal cells from A/J and B10.A mice had a similar ability to kill trophozoites. The capacity of B10.A to mount inflammatory responses was greater than that of A/J. A/J were more immunosuppressed than B10.A during the infection, particularly at mucosal sites. Macrophage-like suppressor cells were shown to be the mediators of this suppression.