The phylum Annelida comprises primitive coelomates that possess specially developed cellular immunity against pathogens. Active phagocytosis by coelomocytes occurs in the struggle against bacteria in Polychaeta and Oligochaeta. Encapsulation plays an important role in defense against parasites, and experimental studies have demonstrated that cooperation between different coelomocyte populations occurs in this process. Spontaneous cytotoxicity of coelomocytes against xenogenic or allogenic cells is analogous with that of vertebrate natural killer cells. Graft rejection is a model for studying the activity of these cells. Accelerated rejection following multiple transplantation reveals that the cellular immune defense system has a short-term memory. In humoral immunity, agglutinins aggregate foreign material and their level is enhanced by antigens; in Annelida, however, no specificity analogous to vertebrate antibodies has been revealed, except for weak specificity of some antigen-binding proteins. Hemolytic substances have been detected, particularly in Oligochaeta, where a fetidin possesses bactericidal activity. Lysozyme and some antibacterial proteins also occur in Polychaeta. Annelida react to physical and chemical insults by various processes. These responses are mainly due to synthesis of stress-induced proteins, inhibition of enzyme activity, and modulation (inhibition or stimulation) of the activity of enzymes involved in the detoxification of xenobiotics. Moreover, these responses frequently differ from those of vertebrates, particularly in terms of the nature of inducers. In other respects, these responses are extremely variable in Annelida, even in closely related species.

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The phylum Annelida comprises primitive coelomates that possess specially developed cellular immunity against pathogens. Active phagocytosis by coelomocytes occurs in the struggle against bacteria in Polychaeta and Oligochaeta. Encapsulation plays an important role in defense against parasites, and experimental studies have demonstrated that cooperation between different coelomocyte populations occurs in this process. Spontaneous cytotoxicity of coelomocytes against xenogenic or allogenic cells is analogous with that of vertebrate natural killer cells. Graft rejection is a model for studying the activity of these cells. Accelerated rejection following multiple transplantation reveals that the cellular immune defense system has a short-term memory. In humoral immunity, agglutinins aggregate foreign material and their level is enhanced by antigens; in Annelida, however, no specificity analogous to vertebrate antibodies has been revealed, except for weak specificity of some antigen-binding proteins. Hemolytic substances have been detected, particularly in Oligochaeta, where a fetidin possesses bactericidal activity. Lysozyme and some antibacterial proteins also occur in Polychaeta. Annelida react to physical and chemical insults by various processes. These responses are mainly due to synthesis of stress-induced proteins, inhibition of enzyme activity, and modulation (inhibition or stimulation) of the activity of enzymes involved in the detoxification of xenobiotics. Moreover, these responses frequently differ from those of vertebrates, particularly in terms of the nature of inducers. In other respects, these responses are extremely variable in Annelida, even in closely related species. Reviews / Synthèses 253 Résumé : Les annélides sont des coelomates primitifs dont l'immunité cellulaire contre les agents pathogènes est particulièrement développée. La phagocytose intense opérée par les coelomocytes assure la lutte contre les bactéries, aussi bien chez les polychètes que chez les oligochètes. L'encapsulation intervient davantage dans la lutte contre les parasites. Des expériences ont mis en lumière la coopération de diverses populations de coelomocytes dans ce processus. La cytotoxicité spontanée des coelomocytes contre les cellules xénogènes et allogènes n'est pas sans rappeler celle des cellules lymphocytes tueurs des vertébrés. Le rejet de greffe peut servir de modèle dans l'étude de l'activité de ces cellules. À la suite de greffes consécutives, le temps de rejet devient de plus en plus court, ce qui reflète la mémoire à court terme des cellules du système immunitaire. Dans l'immunité humorale, les agglutinines agglomèrent des particules étrangères et leur teneur est stimulée par ces antigènes. Cependant, chez les annélides, il ne semble pas y avoir de spécificité comparable à celle des anticorps de vertébrés, sauf peut-être une faible spécificité dans le cas de certaines protéines qui se lient aux antigènes. Des substances hémolytiques ont été détectées, particulièrement chez des oligochè-tes où a également été ...

This study constitutes the first report of a biochemical characterization, involving both substrates and inhibitors and electrophoretic analysis, of a cholinesterase (ChE) from a polychaete annelid (Nereis diversicolor). The ChE of N. diversicolor appears to be an acetylcholinesterase (AChE); i.e., it hydrolyzes acetylthiocholine iodide at a higher rate than other substrates and is inhibited by eserine but not by iso-OMPA. The ChEs of Eisenia fetida are different from that of N. diversicolor and include at least two types of PrChEs. The AChE activity is located principally in the anterior region of the worm (head) in N. diversicolor, whereas the ChE activity of E. fetida is located throughout the body. The electrophoretic characterization of N. diversicolor and E. fetida ChEs showed, respectively, six and two isoforms with disc-PAGE, and three (55,000, 47,000, and 17,000) and five molecular forms (628,000, 301,000, 235,000, 106,000, and 53,800) with PAGGE; substantial activity remained at the top of the PAGGE gel in both species.

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