ISSN:0373-4137    

DOI:10.1080/11250009209386659

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Studies of immunoevolution have revealed diverse strategies within the animal kingdom. The immune system evolved to prevent the threat of extinction by microbial pathogens. Phagocytosis is the most ancient response and at other phylogenetic levels the complexity of immune responses reflects the level of species development. Whether vertebrate immunocytes evolved from invertebrate leukocytes is still questionable without firm information concerning the structural and functional properties of their receptors. Antibodies appear exclusively in vertebrates, however serological and biochemical evidence reveals members of the tg superfamily among certain invertebrates. Cytotoxic cell immunity with limited T cell receptor‐major histocompatibility complex (TCR‐MHC) repertoire could have developed at an early stage of invertebrate evolution. Specificity and anamnesis arc considered hallmarks of induced immune responses and there is evidence for both with respect to cellular and humoral responses in invertebrates. Cytokines, which are released by a variety of activated immune cells, exert profound effects on cells of the immune system and the host defense system in general. They seemed to have evolved early. Future research must emphasize a search for pattern recognition receptors and those receptors which are determined by rearranging gene families.

ISSN:0373-4137    

DOI:10.1080/11250009209386660

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The internal defence system of gastropod molluscs is able to discriminate between self and non‐self. The recognition is carried out principally by both the cellular and humoral components of the haemolymph. Together with freely circulating haemocytes, other defence cells are found scattered throughout the tissue or localized in organs. The present review refers primarily toPlanorbarius corneus, since the defence mechanisms presented by this animal are typical of those of the other gastropods studied.P. corneuspresents two circulating haemocytes: the spreading (SH) and the round haemocytes (RH); in other gastropods only one cell type is described, and this can be considered as a spreading haemocyte. The haemocytes derive both from a haematopoietic organ and from mature circulating haemocytes. The SH show phagocytic properties, adhere to glass, produce agglutinins, bind Con A and contain muramic acid. The RH have non phagocytic properties, do not adhere to glass, form rosettes with sheep red blood cells, are stimulated to proliferate by PHA and present numerous typical markers of vertebrate T lymphocytes. RH are also able to lyse51Cr pre‐labeled K562 target cells in a classical, short‐term, natural cytotoxicity test, and this function is modulated by human recombinant interleukin‐2. Furthermore, SH and RH play a role in the recognition of foreign tissue, the SH are able to encapsulate and phagocytize foreign material, and the RH, with their NK (natural killer)‐like activity, may act like the vertebrate cytotoxic T lymphocytes or NK cells. Thus, it is possible to conclude that RH have characteristics reminiscent of vertebrate T lymphocytes, while SH belong to the category of macrophages. With regards to the humoral component, different factors, such as lysosomal enzymes, lysins and agglutinins or lectins, have been described. InP. corneus, a natural glycoprotein agglutinin has been isolated, whose carbohydrate component contains muramic rather than sialic acid. Moreover, an induced bacterial agglutinin has been purified, although this induction is relatively rare in gastropods. Lysozyme‐like molecules have also been detected and they act like alarm molecules in inflammatory reactions. Taken together, the humoral and cellular investigations, the bacterial clearance studies and the specific responses observed in transplantation experiments are all in favour of the presence of a memory‐type response of short duration. Finally, interrelations appear to exist between the immune and neuroendocrinesystems.ACTH and ß‐endorphin‐immunoreactive molecules have been detected in serum and SH, and these molecules appear to play a physiological role in the process of phagocytosis and in stress response.

ISSN:0373-4137    

DOI:10.1080/11250009209386661

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

It is commonly agreed that invertebrates lack functional antibodies, but still they can efficiently combat and kill parasites trying to gain entry into the body cavity. Often parasites are melanized in the arthropod haemocoel and thus the enzyme responsible for this melanization, phenoloxidase, has been believed to be involved in host defence. Phenoloxidase is present in arthropods as a zymogen and is activated by microbial polysaccharides in a stepwise process involving proteolytic enzymes. In crustaceans it appears that the proPO‐system upon activation produces factors which are involved in the communication between different blood cells. In this article the role of the proPO‐system in host defence is reviewed as well as some of the properties of individual proPO‐components.

ISSN:0373-4137    

DOI:10.1080/11250009209386662

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A lectin‐membrane receptor system is described during capsule formation in the mantis shrimpSquilla mantis, as a model for studying immunological defense in arthropods. The following topics, in particular, are emphasized: the importance of induced lectins in recognition of ≪self≫ by hemocytes; the biochemical characteristics of oligosaccharides of foreign bodies in the mechanism; the importance of monoclonal antibodies in purification of lectins and their localization.

ISSN:0373-4137    

DOI:10.1080/11250009209386663

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Echinoderms possess factors responsible for lysis of target cells. Information on their nature, occurrence, physical and chemical properties and biological role are summarized. Further results on binding properties to surface components are discussed, including a hypothetical explanation both for hemolysin‐target interaction and regulation.

ISSN:0373-4137    

DOI:10.1080/11250009209386664

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The three types of intraspecific histocompatibility in ascidians ‐fusibility, allograft rejection or retention, and cell contact reaction with mutual lysis ‐ are reviewed and compared under both genetic and histological profiles. The differences between solitary and colonial species are outlined. The genetics of fusibility in different populations ofBotryllus schlossenis reconsidered with special reference to its bearing on sexual incompatibility, also in the light of new data. The different modes of allorejection are discussed with regard to the cellular and humoral factors involved. Some histological data on nonfusion reactions inB. schlossertare presented. The difficulties of finding a unifying model for the three types of ascidian alloreactivity are outlined.

ISSN:0373-4137    

DOI:10.1080/11250009209386665

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Specific immunological recognition is not solely a vertebrate trait. Many invertebrates exhibit adaptive histocompatibility responses that bear considerable similarity to venebrate immune reactions. According to our postulate the adaptive immune systems of higher (vertebrate) animals evolved directly from more primitive systems of recognition that are still expressed among advanced invertebrates. If this hypothesis proves to be true, invertebrates may assume an important role as model systems for the analysis of fundamental immunological mechanisms that remain disguised by the complexity of vertebrate systems. Before such invertebrate models can be applied to the rationalization of complex problems, the evolutionary homology of vertebrate and invertebrate immunorecognition must be confirmed. Past studies have demonstrated substantial physiological similarities between invertebrate and vertebrate immunity. However, such functional similarities might also reflect the convergent evolution of otherwise unrelated systems. Convergent evolution would seem unquestionable if we consider that different phyla are included in ≪advanced invertebrates≫. Only detailed molecular comparisons will confirm true homology. Tunicates represent the closest extant ancestors of the vertebrates; they therefore have the greatest chance of yielding identifiable molecular homologies with vertebrate immune‐related molecules. Currently we are analysing the immune system of tunicates with the view toward identifying such homologies. Our work does not assume that invertebrate recognition structures share similarity with their vertebrate equivalents. Instead, we plan to identify tunicate recognition structures in the context of their native system. This approach has a greater chance of success in fulfilling the goal of identifying invertebrate immunorecognition molecules.

ISSN:0373-4137    

DOI:10.1080/11250009209386666

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In invertebrates, cytotoxicity can be an efficient natural defence system. Lysins can be secreted in the body fluids or act at the membrane level of the effector cells. Hemocytes appear to be responsible for the cytotoxic response to foreign, broad, or specific stimuli. The mechanisms by which lysins are released and function are not yet very well characterized. The findings about cell mediated contact dependent cytotoxicity suggest that multiple mechanisms must be considered. In allo‐ and xenogeneic reactions the specificity of cytotoxic mechanisms have been shown, In tunicates, humoral lysins have not been observed. Cytotoxic hemocytes, responsible for allo‐ and xenogeneic reactions, appear to be involved in graft rejections. Some properties of tunicate hemocyte cytotoxicity have been examined inCiona intestinalisusing erythrocyte targets. The reaction is fast, calcium‐dependent, behaves sigmoidally according to temperature, reaches a maximum at 37° C, and depends on membrane contact. Individual variability in lytic capacity ofCionaspecimens suggests that, as in the other invertebrate species, not all the hemocytes are cytotoxic. Sphingomyelin capacity to inhibit the reaction shows functional analogies with the pore‐forming hemolysins of echinoderm and polychaete species. However, it is not excluded that a hemocyte phospholipase may provoke the lysis of the target cell membrane. Thus the hypothesis is supported that a NK‐like activity appears early in the evolution thus contributing to the maintenance of homeostasis, and developing immunity.

ISSN:0373-4137    

DOI:10.1080/11250009209386667

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The production of neurohormone peptides by blood cells in a protochordate, the ascidianStyela plicata, is demonstrated for the first time using immunocytochemical techniques. In particular, neuropeptide Y (NPY)‐like immunoreactivity is localized in some blood cell types such as granular leukocytes and lymphocytes. The possible function of NPY in the ascidian blood is discussed, as well as the relationships between the immune and neuroendocrine systems.

ISSN:0373-4137    

DOI:10.1080/11250009209386668

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor