Analysis of two IgM isotypes in Atlantic salmon and brown trout.
ABSTRACT Atlantic salmon (Salmo salar) possesses two distinct subpopulations of polymeric IgM which are separable by anion exchange chromatography. Consistent with this finding there are two isotypic IgM heavy chain genes, CmuA and CmuB, in the genome of this species, presumably as a result of ancestral tetraploidy. In the present study it was shown that IgM of brown trout (Salmo trutta) is also separated into two subpopulations by anion exchange chromatography, while IgM of rainbow trout (Oncorhynchus mykiss) and Arctic char (Salvelinus alpinus) are eluted in one peak. Molecular cloning of IgM heavy chain cDNAs from brown trout revealed messages of two distinct constant region genes, named CmuA and CmuB. As deduced from the translated cDNA sequences (and in agreement with isoelectric focusing of the corresponding proteins) the mean pI values of the heavy chains in brown trout differ with only 0.14 units, in comparison to a 0.67 unit difference in salmon. Based on the present sequence analysis we suggest that an additional cysteine near the C-terminus of CmuB is critical in relation to the fractionation of IgM by anion exchange chromatography, for example by altering the overall structure of the IgM polymer and the exposure of charged residues. Most likely, the Cmu subvariant with the characteristic extra cysteine residue arose in the ancestor of Atlantic salmon and brown trout, i.e. after the three genera Salmo, Oncorhynchus and Salvelinus radiated.
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ABSTRACT: Sharks and skates are representatives of the earliest vertebrates with an immune system based on V(D)J rearrangement. They possess a unique Ig gene organization consisting of 15 to >50 individual IgM loci, each with one VH, two DH, one JH, and one set of constant region exons. The present study attempts to understand how multiple Ig genes are regulated with respect to rearrangement initiation and to targeting during somatic hypermutation. The linkage of three single-copy IgH genes was determined, and single-cell genomic PCR studies in a neonatal animal were used to examine any relationship between relative gene position and likelihood of rearrangement. Our results show that one to three IgH genes are activated independently of linkage or allelic position and the data best fit with a probability model based on the hypothesis that V(D)J rearrangement occurs as a sequence of trials within the B cell. In the neonatal cell set, two closely related IgH, G2A, and G2B, rearranged at similar frequencies, and their membrane forms were expressed at similar levels, like in other young animals. However, older animals displayed a bias in favor of the G2A isotype, which suggests that although rearrangement at G2A and G2B was randomly initiated during primary repertoire generation, the two very similar IgM sequences appear to be differentially expressed with age and exposure to Ag. We performed genomic single-cell PCR on B cells from an immunized individual to study activation-induced cytidine deaminase targeting and found that hypermutation, like V(D)J rearrangement, occurred independently among the many shark IgH.The Journal of Immunology 09/2011; 187(5):2492-501. · 5.52 Impact Factor
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ABSTRACT: The Brazilian organic food sector has experienced important growth during the last two decades. Brazilian smallholders, however, are facing huge challenges to enter and benefit from this growth in a sustainable way. Combining the lens of New Institutional Economics and socio-anthropology, we analyse six experiences of Brazilian smallholders who converted to organics in the 1990s’. Three different food systems are featured in this analysis: an alternative food system, which is strongly interwoven with the Brazilian Agro-ecological movement and two commercial food procurement systems oriented towards domestic and an export markets driven mainly by supermarket chains. The analytical focus was on 1) the governance of these food systems, 2) the constraints farmers are facing within these food systems and, 3) the benefits that they can expect from market inclusion. We highlighted the roles that NGOs, Faith-based organisations and public-related agencies play in supporting the inclusion of smallholders into all three food systems. We confirmed the arguments in support of pursuing the agro-ecological development based model in Brazil, but underlined that there is a critical lack of support for famers included in the commercial market-oriented food systems. Such a lack is even more critical as the food systems driven by expanding supermarket chains are characterised by strong asymmetric power relations at the expense of smallholders. Considering the reluctance of NGOs and Faith-based organisations to support these farmers, we call for efforts to be made to provide a policy framework to enable public related entities to secure sustainable inclusion into these systems and exit strategies for those experiencing exclusion from these highly competitive food systems.Journal of Rural Studies - J RURAL STUD. 01/2012;
Article: Immunity to fish rhabdoviruses.[show abstract] [hide abstract]
ABSTRACT: Members of the family Rhabdoviridae are single-stranded RNA viruses and globally important pathogens of wild and cultured fish and thus relatively well studied in their respective hosts or other model systems. Here, we review the protective immune mechanisms that fish mount in response to rhabdovirus infections. Teleost fish possess the principal components of innate and adaptive immunity found in other vertebrates. Neutralizing antibodies are critical for long-term protection from fish rhabdoviruses, but several studies also indicate a role for cell-mediated immunity. Survival of acute rhabdoviral infection is also dependent on innate immunity, particularly the interferon (IFN) system that is rapidly induced in response to infection. Paradoxically, rhabdoviruses are sensitive to the effects of IFN but virulent rhabdoviruses can continue to replicate owing to the abilities of the matrix (M) protein to mediate host-cell shutoff and the non‑virion (NV) protein to subvert programmed cell death and suppress functional IFN. While many basic features of the fish immune response to rhabdovirus infections are becoming better understood, much less is known about how factors in the environment affect the ecology of rhabdovirus infections in natural populations of aquatic animals.Viruses 01/2012; 4(1):140-66. · 2.51 Impact Factor