Substances involved in the natural resistance of fish to infection–A review

Abstract

Natural 'antibodies' are substances found in the blood of animals that have not been immunised against infective agents. However, exposure to these agents or to cross-reacting antigens may well have taken place. Fish contain naturally-occurring, relatively nonspecific, lectin-like proteins or glycoproteins, which are distinct from immunoglobulins, and which react with a wide variety ofantigens and may confer some degree of immunity against natural infection. In most cases the cause of the antigenic stimulus is not obvious although the formation of these 'antibodies' may have been brought about by exposure to various micro-organisms. Many of these antibody-like molecules behave in a similar manner to immune antibodies or immunoglobulins and cross-react with specific carbohydrate moieties on the cell walls of bacteria, erythrocytes and certain other cellular antigens, due to the presence of similar antigenic determinants.It is difficult to ascribe an appropriatc dcfinition to the term 'natural antibody'. In fish, thesc 'antibodies' have been so designated on the basis of functional rather than structural criteria. Such naturally-occurring, low grade, antibody-like ' immune ' substances include 'acute phase' proteins, lysozyme and chitinase, interferon, agglutinins, lysins, complement and properdin, precipitins, and non-immunoglobulin, lectin-like molecules. In addition to the above non-immunoglobulin materials, natural immunoglobulins identifiable as IgM have also been reported in fish. Furthermore, mucus contains many biochemical agents capable of reaction against infective organisms and thus providing the host with an immediate or a first line of defence mechanism.This review compiles some of the relevant information in the literature concerned with natural 'immune' substances, present in the serum and mucus of fish, involved in protection against pathogens. Wherever possible the basic physicochemical properties of these substances are indicated and their potential immunobiological functions discussed.

A Teleost Polymeric Ig Receptor Exhibiting Two Ig-Like Domains Transports Tetrameric IgM into the Skin

“…In mammals and avian species, the mucosal Ig is transported by a polymeric Ig receptor (pIgR) 4 through the monolayer of epithelia into the mucosal secretions (1,2,(21)(22)(23)(24)(25). However, mammals and avian species do not express pIgR in the skin.…”

“…One of the most important defensive molecules in this system is secretory Ig, predominantly IgA (3). In species of teleost fish, the skin also has important immunological roles against aquatic infectious agents, as does other mucosal tissues such as the gut (4). In fact, tetrameric IgM, but not dimeric IgA, exists in the skin and gut mucus of teleost fish (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15).…”

Reponse immunitaire humorale induite par le virus de la necrose pancreatique infectieuse (VNPI) chez la truite mouchetee (Salvelinus fontinalis L ) et caracterisation de l immunoglobuline produite

“…Cependant, les mécanismes qui entrent en jeu pour moduler la production d'anticorps demeurent peu clairs (Avtalion et al. 1976 (Ingram, 1980). En second lieu, il y a l'immunité acquise et spécifique qui s'affiche par la réponse humorale caractérisée par la production d'immunoglobulines et par la réponse cellulaire connue par les phénomènes de rejet de greffe (Dorson, 1984 …”

“…(Ingram, 1980 (Ellis,1982). D'autres études menées sur ces cellules phagocytaires (Ellis,1977a;Secombes, 1986) (Alexander, 1980;Alexander et Shakarchi, 1986 (Ingram, 1980;Ourth, 1980;Rijkers, 1982).…”

Antibacterial Activity of Skin and Intestinal Mucus of Five Different Freshwater Fish Species Viz., Channa striatus, C. micropeltes, C. marulius, C. Punctatus and C. gachua

“…The skin acts as a mechanical barrier by preventing the entry of microbes into the body [3]. Potentially valuable proteins and enzymes are present in the fish by products [4] and these compounds and the antagonistic bacteria help prevention of invading bacterial diseases. Virtually all fishes are covered with integumental mucus that is involved in many aspects of their biology, ranging from disease resistance to rearing of youngones to shelter and locomotion.…”