Comparison Of Serum Lectin In Seven Cultured Fishes And MBL MRNA Express Lever In Different Tissues Of Grass Carp

Fish have a relatively variable capacity for antibody-mediated immunity, the innate immunity is expected to be very important in fish. Innate immunity system consists of a complex of consitutively expressed components whose functions are to axt as a first-line defense against invading pathogens and subsequently to interact with the adaptive immune system. One element of the innate immune system is a series of C-type lectins, the collectins, which bind to carbohydrates on the surface of invading pathogens and subsequently intact with other components of the immune system, such as the complement system and cell surface receptors on phagocytic cells.Mannose-binding lectin(MBL) is a collectin synthesized by hepatocytes, participates in the innate immune system as an activator of the complement system and as an actibator of the certain carbohydrate structures on microorganisms. The MBL of mammalian and bird all contain two conserved cystenines in the N-terminal region, and some contain a third cysteine. These cysteines are involved in the formation of subunite composed of three identical polypeptide chains and in the oligomerization of these subunits. The CRD is approximately 120 amino acids long and contains several invariant or explanation for the conserved sequence motif found in this domain.The hemagglutination activity indicated that sera from seven cultured fishes had different agglutinability to several kinds of animal erythrocyte. The sera from Monopteurs albus, mature Ctenopharygodon idllus and Aristichthys nobilis had the highest agglutinability. The agglutinability of fish sera increased when rabbit erythrocyte was treated with 1U/ml trypsin. The fish serum lectin was sensitive to EDTA, 3 -mercaptanethanol, NaIO4, trypsin and their agglutinability could be inhibited by mannose, galactose and lactose.The cross-reactivity of seven cultured fishes serum lectin and Wuchang Fish anti-viral lectin-like protein(WAL) Ab was analysised by double immunodiffusion test and Western Blot. In double immunodiffusion test, precipitation lines were produced between rabbit specific anti-serum against WAL and sera from Ctenopharygodon idllus, Carassius auratus, Aristichthys nobilis, Hypophthalmichthys molitrix. In Western Blot, specific bands could be observed in the sera from mature Ctenopharygodon idllus, Aristichthys nobilis, Hypophthalmichthys molitri, and the Mr was about 25 000. The result of bacteria hemagglutination activity indicated that sera from seven cultured fishes had different agglutinability to several kinds of bacteria, the sera from Monopteurs albus, mature Ctenopharygodon idllus and Aristichthys nobilis had the highest agglutinability. The fishserum lectin was sensitive to EDTA, β-mercaptanethanol, NaIO4, and their agglutinability could be inhibited by mannose, galactose and lactose.Total mRNA was isolated from the spleen of carp (Cyprinus carpio) and spleen, liver, gills, thymus, head kidney and kidney of mature and immature grass carp(Ctenopharygodon idllus). The cDNA of MBL was obtained by RT-PCR using total mRNA from the spleen of carp as template. Such cDNA was labled with 32P and used as probe for northern analysis. Autoradiographic signals were quantified by densitometry analysis. The results showed that MBL was high expressed in the spleen and liver and low in gills, thymus, head kidney and kidney of mature Ctenopharygodon idllus, and MBL was much lower expressed in spleen and liver of immature grass carp than those of mature grass carp.