The recent realization that viruses within the family Iridoviridae may contribute to the worldwide decline in amphibians makes it urgent to understand amphibian antiviral immune defenses. We present ...evidence that establishes the frog
Xenopus laevis as an important model with which to study anti-iridovirus immunity. Adults resist high doses of FV3 infection, showing only transitory signs of pathology. By contrast, naturally MHC class-I-deficient tadpoles are highly susceptible to FV3 infection. Monitoring of viral DNA by PCR indicates a preferential localization of FV3 DNA in the kidney, with the inbred MHC homozygous J strain appearing to be more susceptible. Clearance of virus as measured by detection of FV3 DNA and also the disappearance of pathological and behavioral symptoms of infection, acceleration of viral clearance, and detection of IgY anti-FV3 antibodies after a second injection of FV3 are all consistent with the involvement of both cellular and humoral adaptive antiviral immune responses.
•The CD4 co-receptor serves as a receptor for IL-16.•Recombinant human IL-16 binds to a substantial portion of Xenopus splenic lymphocytes.•Recombinant human IL-16 appears to preferentially promote ...lymphocyte infiltration in the peritoneum in Xenopus.•Xenopus CD8− lymphocytes increase MHC class II gene expression upon incubation with human IL-16.
The D1 domain of the CD4 co-receptor interacts with MHC class II during Helper CD4+ Th-cell activation and effector function in all gnathostomes but the sequence and structure of this region are not well conserved through phylogeny. Conversely, the proximal D4 domain of CD4 is the binding site of the cytokine IL-16 and is highly conserved, allowing for promiscuous binding of IL-16 to CD4 between disparate gnathostomes. We report here that recombinant human IL-16 (rhIL-16) bound to Xenopus lymphocytes to allow separation on a magnetic column. Incubation with rhIL-16 resulted in an increased expression of MHC class II mRNA by Xenopus CD8− cells more than by CD8+ cells. An in vivo assay demonstrated that rhIL-16 can recruit lymphocytes of Xenopus frogs. Our data suggest that a subset of Xenopus laevis lymphocytes express a CD4 homolog on their surface that is capable of binding IL-16. These results imply that CD4 most likely arose from a primordial cytokine receptor.
Xenopus serves as an experimental model to evaluate the contribution of adaptive immunity in host susceptibility to emerging ranaviral diseases that may contribute to amphibian population declines. ...It has been previously shown that following a secondary infection with the ranavirus frog virus 3 (FV3), adult
Xenopus more rapidly clear FV3 and generate specific anti-FV3 IgY antibodies. We have further evaluated the potency and persistence of the
Xenopus antibody response against FV3. Frogs inoculated with FV3 (without adjuvant) up to 15 months after priming produce specific, thymus-dependent anti-FV3 IgY antibodies detectable from 10 days to 8 weeks post-infection. These antisera from boosted frogs are neutralizing in vitro and provide partial passive protection to susceptible larvae when they are injected a few minutes before FV3 inoculation. These results with
Xenopus suggest that other anuran amphibians are likely to develop effective long-lasting protective humoral immunity after an initial viral exposure.
In vertebrates from man to frogs, the heat shock protein (hsp) gp96 elicits T-cell responses against antigenic peptides that it chaperones. In Xenopus, immunization with gp96 purified from normal ...tissues accelerates rejection of MHC identical, minor histocompatibility (H) antigen-disparate skin grafts in vivo and induces MHC-restricted CTL responses in vitro. Also in Xenopus, gp96 derived from MHC class I-negative tumors elicits peptide-specific responses against these tumors in vivo and MHC-unrestricted CD8 killing in vitro. We have developed an adoptive cell transfer protocol to further characterize these gp96-stimulated Xenopus effectors in vivo.
Carboxyfluorescein diacetate succinimidyl ester (CFSE)-stained splenocytes from cloned LG-6 donor frogs immunized with gp96 purified from minor H-antigen-disparate LG-15 tissues were transferred into LG-6 recipients bearing a LG-15 minor H antigen (ag)-disparate skin graft. Primed anti-LG-15 but not naive CFSE T cells accumulated and divided in the spleen of allografted recipients to a greater extent than in those of autografted recipients. Similar accumulation and division occurred when CD8 T cells primed by 15/0 tumor-derived gp96 were transferred to an isogeneic recipient bearing the same MHC class I-negative tumor. Furthermore, the transfer of such primed antitumor splenocytes into naive recipients before tumor challenge delayed the appearance of tumors.
These data provide new in vivo evidence that in frogs as in mammals, gp96 can prime CD8 T cells against antigens they chaperone. In addition, at least in Xenopus, gp96 can prime CD8(+) T-cell effectors that are not MHC restricted.
Little is known about the changes in the immune system that coincide with the annual cycle of hibernating mammals. This study investigates classical pathway complement activity in the serum of the ...golden-mantled ground squirrel, a mammalian hibernator. Complement activity varied significantly among discreet stages of the annual cycle and is lowest during torpor and greatest during stages of arousal. C3 mRNA levels follow a pattern similar to that of complement-mediated hemolysis throughout the year but do not vary significantly among hibernation states. The classical pathway of the serum complement system is able to function in vitro at 5
°C, although at a slower rate than at 34
°C. The classical pathway of the serum complement system is active throughout all phases of the annual cycle of the golden-mantled ground squirrel.
Biology Department, Stonehill College, Easton, Massachusetts
Address for reprint requests and other correspondence: G. D. Maniero, Biology Dept., Stonehill College, 320 Washington St., Easton, MA ...02357 (e-mail: gmaniero{at}stonehill.edu )
The immune system is a vital physiological component that affords animals protection from disease and is composed of innate and adaptive mechanisms that rely on cellular and dissolved components. The serum complement system is a series of dissolved proteins that protect against a variety of pathogens. The activity of complement in serum can be determined by its ability to lyse red blood cells in vitro. Here, we describe a modification of a standard complement hemolysis assay that makes an interesting and informative laboratory exercise suitable for a variety of courses including physiology.
Key words: red blood cells; immune system; hemolysis; CH 50 ; heat labile
The SPES Radioactive Ion Beam (RIB) facility at INFN-LNL is in the construction phase. It is based on the ISOL method with an UCx Direct Target able to sustain a power of 10 kW. The primary proton ...beam is delivered by a high current Cyclotron accelerator, with energy 35-70 MeV and a beam current of 0.2-0.5 mA. Neutron-rich radioactive ions will be produced by proton induced Uranium fission in the UCx target at an expected fission rate in the order of 10 super(13) fissions per second. The exotic isotopes will be re-accelerated by the ALPI superconducting LINAC at energies of 10A MeV and higher, for masses in the region A=130 amu at expected rate on the secondary target of 10 super(7) - 10 super(9) pps. The SPES project has the aim to provide high intensity and high-quality beams of neutron-rich nuclei as well as to develop an interdisciplinary research center based on the cyclotron proton beam.
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