An “immunome” gene panel for transcriptomic analysis of
immune
defence
activities
in
the
teleost
sea
bass
(Dicentrarchus labrax L.): a review.
E. RANDELLI, F. BUONOCORE, D. CASANI, A. M. FAUSTO & G.
SCAPIGLIATI*
Dipartimento di Scienze Ambientali, Università della Tuscia, 01100
Viterbo, Italy.
*Corresponding author: Giuseppe Scapigliati, Dipartimento di Scienze Ambientali,
Università della Tuscia, Largo dell'Università, 01100Viterbo, Italy
Tel./Fax. +39-0761-357029 Email: scapigg@unitus.it
ABSTRACT
Teleost fish are the oldest living vertebrates displaying a morphological and
functional immune system conserved until mammals, thus representing a useful
model for evolutionary studies. Teleosts are increasingly employed as experimental
animal species for studies on physiological activities of vertebrates, and are widely
used in the aquaculture industry. Due to its importance as high quality food, the sea
bass is, at present, one of the most important farmed species in the Mediterranean sea
and many studies reported on the morphological and functional organisation of
immune defences with the aim of controlling its health in farming conditions. From
these studies, a panel of genes coding for main immunomodulatory peptides of innate
and acquired defences is available and constituted, at present, by genes coding for
innate defences, for acquired defences, and for other immune-related activities. In this
review all these genes are collected and defined as the sea bass “immunome”, that is
analysed in an evolutionary context.
Keywords: Sea bass, Dicentrarchus labrax, immune system, transcriptome,
immunome.
INTRODUCTION
Survival of an organism depends upon an effective defence against foreign invaders.
In all species living today, the defence mechanisms have evolved into an effective
machine that has enabled their successful survival and their adaptive radiation. Most
micro-organisms such as bacteria, parasites, fungi and viruses have represented an
enormous source of aggressors during the evolution of metazoans, usually responsible
either directly or indirectly for multiple causes of infection.
Since their appearance, micro-organisms and metazoans have been and are still
engaged in a never ending arms race, which has led to the evolution of protection
mechanisms in vertebrates and pathogenicity mechanisms in microbes. It has been
suggested that the diverse evasive strategies of micro-organisms to their host have
acted as inducers of vertebrate defence evolution (Castro and Gonzalez, 2001).
Higher Metazoa are represented by Vertebrates, which can be considered at present as
the group of species in which evolution reached its maximum. Living vertebrates are
around 40.000 species, half of which are bony fish. Bony fish are in full adaptive
radiation and are present in every aquatic environment ranging from warm tropical
freshwaters, to polar seas, to abyssal depths.
It should be noted that in all environmental conditions animal species must fight
invading microbes. Hence, the immune defence is an indispensible feature under the
control of genes which can mutate and evolve under selective pressures, but which
must leave immune defences fully functional. Therefore, studies on the evolution of
immune responses among vertebrates will be a valuable tool for the understanding of
conserved responses, conserved genes, conserved molecules, and conserved
conformational epitopes.
In addition, teleost fish represent an indispensible two-in-one model for studies in the
function of immune activities, since have a larval stage during which they must rely
solely on innate activities, and more mature stages where both innate and acquired
defences are functional.
Due to its importance for aquaculture, sea bass rearing is continuously improving
mostly in southern European countries. Much work is performed on the prevention of
the main bacterial and viral pathologies that affect this species in aquaculture. The
current status of knowledge on sea bass immune system has been recently reported
(Scapigliati et al. 2006). Sea bass may represent a reference animal model for studies
on the immune system of vertebrates, since it is, at present, the only marine species
for which are available several cellular and molecular markers represented by
monoclonal antibodies for B- and T- lymphocytes, and nucleotide probes for several
immunomodulatory molecules. In addition, the conditions for culturing of leucocytes
are known for this species, and this allowed studies on “in vitro” reactions of
leucocytes to particular stimulation.
In recent years, with the increasing knowledge on gene cloning technologies, many
genes coding for immunoregulatory molecules and homologous to their mammalian
counterparts have been discovered in teleost fish, including sea bass, and this review
summarizes the knowledge in this species (Table 1). The selected genes code for
molecules endowed with pivotal immune defence activities, and this panel will be
henceforth defined as the Dicentrarchus labrax immunome.