Skin homeostasis is critical to preserve animal integrity. Although the skin of most vertebrates is known to contain a skin-associated lymphoid tissue (SALT), very little is known about skin B-cell responses as well as their evolutionary origins. Teleost fish represent the most ancient bony vertebrates containing a SALT. Due to its lack of keratinization, teleost skin possesses living epithelial cells in direct contact with the water medium. Interestingly, teleost SALT structurally resembles that of the gut-associated lymphoid tissue, and it possesses a diverse microbiota. Thus, we hypothesized that, because teleost SALT and gut-associated lymphoid tissue have probably been subjected to similar evolutionary selective forces, their B-cell responses would be analogous. Confirming this hypothesis, we show that IgT, a teleost immunoglobulin specialized in gut immunity, plays the prevailing role in skin mucosal immunity. We found that IgT + B cells represent the major B-cell subset in the skin epidermis and that IgT is mainly present in polymeric form in the skin mucus. Critically, we found that the majority of the skin microbiota are coated with IgT. Moreover, IgT responses against a skin parasite were mainly limited to the skin whereas IgM responses were almost exclusively detected in the serum. Strikingly, we found that the teleost skin mucosa showed key features of mammalian mucosal surfaces exhibiting a mucosa-associated lymphoid tissue. Thus, from an evolutionary viewpoint, our findings suggest that, regardless of their phylogenetic origin and tissue localization, the chief immunoglobulins of all mucosa-associated lymphoid tissue operate under the guidance of primordially conserved principles.evolution | mucosal immunoglobulin | Ichthyophthirius multifiliis | cutaneous

No abstract

No abstract

Freshwater fish are able to mount a protective immune response against the parasite Ichthyophthirius multifiliis (Ich) following a non-lethal exposure. Factors involved in immunity comprise cellular and humoral factors, but antibodies have been suggested to play a prominent role in protection. However, host antibodies have not yet been demonstrated to bind to the parasite in situ. By the use of immunohistochemical techniques, this study demonstrated that IgT and IgM bind to surface structures, including cilia, on the early feeding stage of the parasite in the gills of immune rainbow trout, Oncorhynchus mykiss, shortly (2 h) after invasion. No binding of IgT and no or only a weak binding of IgM was observed on the parasites in the gills of similarly exposed but naïve rainbow trout. This study indicates that antibodies play an important part in the protection of immune fish against Ich although additional humoral and cellular factors may contribute to this reaction.

Rainbow trout Oncorhynchus mykiss were immunised by intra-peritoneal injection using a live vaccine based on Ichthyophthirius multifiliis (Ich) theronts, which previously has shown protection against white spot disease. Samples were taken pre-vaccination and on Day 1, 7, 21 and 28 post-immunisation (p.i.). Expression of immune relevant genes in the liver, spleen and head kidney was monitored by qPCR. To describe the immune reaction following this immunisation, a series of genes encoding cytokines, complement factors, immunoglobulins and acute phase reactants were studied. Genes encoding acute phase reactants in the liver were up-regulated with serum amyloid A (SAA) as the most pronounced with a 2299-fold increase at 24 h p.i. Hepcidin and pre-cerebellin were also up-regulated in the liver 24 h p.i., by 7-and 4-fold, respectively. Complement factors C3, C5 and factor B (Bf) were up-regulated in the spleen and the head kidney 24 h and 28 d p.i. Genes encoding immunoglobulins were not up-regulated, but a specific low titer IgM response (titer 25) against parasite antigens was detected by a modified ELISA 4 wk p.i. KEY WORDS: Vaccine · White spot disease · Fish · Immune response Resale or republication not permitted without written consent of the publisherDis Aquat Org 80: [189][190][191][192][193][194][195][196][197] 2008 A number of investigations have been conducted to elucidate the causative mechanisms involved in protection (Hines & Spira 1974, Clark et al. 1988, Sigh & Buchmann 2001, Wang et al. 2002, Sigh et al. 2004a,b, Xu et al. 2004. Although specific antibodies may play a role in immunity, it is clear that several other immune factors determine the protective state of the fish against this skin parasite (Sigh et al. 2004a). However, the different factors involved in protection, and their relative importance, following vaccination are unknown. The development of a live vaccine conferring high protection towards Ich in rainbow trout (Alishahi & Buchmann 2006) has made it feasible to study immune genes activated upon protective immunisation. Here we describe vaccination of rainbow trout using such a live vaccine and report on the quantitative expression of genes encoding complement factors (C3, C5, Bf), immunoglobulins (IgM, IgT), cytokines (IL-1β(1), IL-6, IFN-γ, TNF-α) and acute phase reactants (transferrin, serum amyloid protein [SAP] hepcidin, trout C-polysaccharide-binding protein [Tcbp], serum amyloid A [SAA], and pre-cerebellin) during development of protection. The measured genes were selected both on account of availability and their possible involvement in an immune response against Ich. Complement factors have previously been shown to play a role in immobilisation of theronts using trout serum in vitro (Buchmann et al. 1999, Sigh & Buchmann 2001. Genes encoding immunoglobulins were chosen in order to detect antibody responses against Ich (Xu et al. 2004). IgT was recently found to be upregulated in a study using a bath vaccination with Yersinia ruckeri (M. Raida & K. Buchmann unp...