The biological bases of invertebrate immune responses have interested scientists for decades, from the first relevant observation by E. Metchnikoff in 1882, who discovered phagocytosis while studying starfish larvae. Invertebrate immunology first began to be appre ciated as an important field in the late 1960s and 1970s. However, in the following years there was much controversy regarding the question: do invertebrates offer insight into the origin of the sophisticated immune responses of the vertebrates? There are several reasons why progress in research on invertebrate immune competence has been painfully slow. One of the main impediments to the progress, as compared to the fast development of knowledge in the vertebrate systems, was the fact that most of the studies concentrated on "whole organism" assays, mainly on grafting tissues between allogeneic partners. Only in the last few years have more and more aspects of invertebrate immunity been investigated on the cellular, biochemical and molecular levels. These studies led to discoveries of novel defense reactions, new pathways of effector mechanisms which are elicited after recognition of "nonself', and complex, sometimes highly polymorphic genetic elements that control invertebrate immune reactions. The importance of invertebrate immunity for understanding "immunology" as a whole, despite the conflicting models and hypotheses, is now much more recognized than before. Although most of the 20 phyla belonging to the inver tebrates have different modes of life, body organizations, habitats occupied, and biochemical patterns, they show striking aspects of exceptional precision for discriminating between self and nonself.
Table of ContentsHumoral Factors in Marine Invertebrates.- References.- Earthworm Immunity.- 1 Introduction.- 2 Cells of the Immune System.- 3 Natural Immunity and Nonspecific Cellular Responses.- 4 Immune Reactions to Transplants: Coelomocyte Responses.- 4.1 Histopathologic Alterations.- 4.1.1 Will Pollution Affect Wound Healing and Graft Rejection?.- 4.1.2 Where Do Coelomocytes Come From?.- 4.1.3 Adoptive Transfer of Accelerated Responses.- 5 Proliferative Response of Coelomocytes to Transplantation Antigens.- 6 Membrane Components Allied to the Ig Superfamily.- 6.1 Phylogeny of the Immunoglobulin Joining (J) Chain.- 7 Communication Between Immune, Nervous and Endocrine Systems.- 8 Cell-Mediated Cytotoxicity.- 9 Mechanisms of Cellular Defense: Adaptive Cellular Response.- 10 Lysozyme-Like Substances.- 10.1 Hemolytic and Hemagglutinating Systems of the Coelomic Fluid.- 10.1.1 Cytolytic Substances.- 10.1.2 Adaptively Formed Substances.- 10.1.3 Tumorostatic Activity of Coelomic Fluid.- 11 Evolution of Immune Responses and Where Earthworms Fit In.- References.- The Prophenoloxidase Activating System and Associated Proteins in Invertebrates.- 1 Introduction.- 2 Components of the Prophenoloxidase Activating System.- 2.1 Prophenoloxidase.- 2.2 Prophenoloxidase Activating Enzyme.- 2.3 Prophenoloxidase Activation Inhibitors.- 2.4 Elicitors and Elicitor-Binding Proteins.- 2.5 Associated Proteins.- 2.5.1 The Cell-Adhesion Protein.- 2.5.2 The Receptor for the ß-1,3-Glucan Binding Protein and the Cell-Adhesion Protein.- 3 Complement-like Proteins.- 4 Clotting Proteins.- 5 Summary.- References.- Inducible Humoral Immune Defense Responses in Insects.- 1 Introduction.- 2 Antibacterial Responses.- 2.1 Lysozyme.- 2.2 Lectins.- 2.3 Cecropins and Allied Factors.- 2.4 Attacins and Allied Factors.- 2.5 Defensins.- 2.6 The Antibacterial Response in the American Cockroach.- 2.7 Hemolin.- 2.8 Unclassified Antibacterial Factors.- 3 The Response to Soluble Proteins.- 4 Concluding Remarks.- References.- Blood Clotting in Invertebrates.- 1 Introduction.- 1.1 Hemostasis and Immunity a Marriage of Convenience.- 2 The Limulus Clotting System.- 2.1 Amebocytes and Clotting.- 2.1.1 The Proteolytic Cascade.- 3 Clotting in Crustaceans and Other Arthropods.- 4 Conclusion.- References.- Immune Function of ?2-Macroglobulin in Invertebrates.- 1 Introduction.- 2 Structure of ?2-Macroglobulin.- 3 The ?2-Macroglobulin Protein Family.- 4 ?2-Macroglobulin in Invertebrates.- 5 Receptor-Mediated Clearance of ?2-Macroglobulin-Protease Complex.- 6 ?2-Macroglobulin in the Blood Cells.- 7 Interaction of ?2-Macroglobulin with the Proteases of the Clotting System of Limulus.- 8 Cytokine-Binding Activities of ?2-Macroglobulin.- 9 The Plasma Based Cytolytic System of Limulus.- 10 ?2-Macroglobulin and the Inactivation of the Proteases of Invading Parasites.- 11 Interaction of the ?2-Macroglobulin with Other Systems of Immunity in Invertebrates.- 12 Evolutionary Considerations.- References.- Host-Parasite Interactions in Molluscs.- 1 Introduction.- 2 Molluscan Internal Defenses.- 3 The Fates of Invading Molluscan Parasites.- 4 How Do Molluscs Respond to Parasite Infections?.- 5 Are Susceptible Snails Simply Incompetent?.- 6 How Does a Parasite Escape Destruction by a Molluscan Host?.- 7 Conclusions.- References.- Clotting and Immune Defense in Limulidae.- 1 Introduction.- 2 Hemolymph.- 3 Hemocytes.- 4 Hemocyte Granules.- 5 Clotting Cascade.- 5.1 Coagulogen and Coagulin.- 5.2 Proclotting Enzyme and Clotting Enzyme.- 5.3 Factor B and Factor $$ \overline B $$.- 5.4 Factor C and Factor $$ \overline C $$.- 5.5 Factor G and Factor $$ \overline G $$.- 6 Protease Inhibitors.- 6.1 Anticoagulants.- 6.1.1 Limulus Intracellular Coagulation Inhibitor, Types 1 and 2 (LICI-1 and -2).- 6.2 Trypsin Inhibitor in the Hemocytes.- 6.3 Inhibitor in Plasma.- 6.3.1 ?2-Macroglobulin.- 7 Transglutaminase and Its Substrates.- 7.1 Transglutaminase.- 7.2 Intracellular Substrates of Transglutaminase.- 8 Antibacterial Substances.- 8.1 Antilipopolysaccharide Factor (ALF).- 8.2 Tachyplesin Family.- 8.3 BigDefensin.- 9 Agglutinins/Lectins.- 9.1 Plasma Agglutinins.- 9.1.1 Limulin/C-Reactive Protein/Carcinoscorpin.- 9.1.2 Polyphemin.- 9.1.3 Lectins from Japanese Horseshoe Crab (Tachypleus tridentatus).- 9.2 Intracellular Agglutinins.- 9.2.1 LPS-Binding Protein (L6).- 9.2.2 Limunectin.- 9.2.3 Limulus 18K Agglutination-Aggregation Factor (18K-LAF).- 10 Summary.- References.- Cytotoxic Activity of Tunicate Hemocytes.- 1 Introduction.- 2 Ascidian Hemocytes.- 3 Multiple Modes of Self/Nonself Recognition and Cytotoxicity.- 3.1 Graft Rejection in Solitary Ascidians. Specific Immunorecognition and Hemocyte Cytocidal Responses to Foreignness.- 3.2 Tunic Reaction to Erythrocyte Subcuticular Injection.- 3.3 Nonfusion Reaction in Colonial Ascidians.- 3.4 Natural Cytocidal Response. In Vitro “Contact Reaction”.- 3.5 In Vitro Spontaneous Hemocyte Cytotoxic Activity Against Mammalian Target Cells.- 3.5.1 Erythrocyte Targets.- 3.5.2 Tumor Cells.- 4 The Hemocytes Involved in Cytotoxic Reactions.- 4.1 Are Immunocompetent Lymphocyte-Like Cells Cytotoxic?.- 4.2 Are Lymphocyte-Like Cells Involved in NFR?.- 4.3 Stem-Cell Function of Lymphocyte-Like Cells.- 4.4 Hemocytes Involved in Botryllid Cytotoxic Reactions.- 5 Hemocytes Involved in the Contact Reaction.- 6 Globular Granulocytes (Morula Cells): Are They Involved in Cytotoxic Reactions?.- 7 Hemocytes with NK-Like Activity.- 7.1 Antierythrocytes.- 7.2 Antitumor.- 8 Conclusions.- References.- Humoral Factors in Tunicates.- 1 Introduction.- 2 Hemagglutinins (Lectins).- 3 Antimicrobial Substances.- 4 Other Humoral Factors.- 5 Humoral Factors Involved in Allogeneic Recognition.- 6 Concluding Remarks.- References.- Molecular Aspects of Immune Reactions in Echinodermata.- 1 Introduction.- 2 Response to Allogeneic Transplants.- 3 Clearance Studies.- 4 Humoral Molecules.- 5 Cytokines.- 6 Immune Effector Cells.- 7 Summary and Concluding Remarks.- References.