Biomedical subjects

D A Raftos

Publications and source records attributed to D A Raftos.

26 records · Page 2Linked to original sources

PubMed1990

In vitro culture of tissue from the tunicate Styela clava.

Pharyngeal explants and circulatory hemocytes from the tunicate Styela clava were cultured in a medium containing tunicate plasma, artificial seawater, RPMI 1640, and antibiotics. Pharyngeal tissue remained viable and proliferated for up to 72 d in vitro. Proliferative activity maintained the pool of hemocytes within explants and facilitated the migration of pharyngeal hemocytes from explants into culture supernatants. The diversity of morphologically distinct cell types within the hemocyte pool of pharyngeal cultures indicated that cell division was followed by regulated differentiation. In contrast to pharyngeal cultures, suspensions of circulatory hemocytes did not survive for prolonged periods in vitro. Proliferative activity could not be detected in circulatory hemocyte cultures. These results are discussed in terms of the differentiation state of hemocytes and the efficacy of culture conditions.

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PubMed1988

The mode of recognition of allogeneic tissue in the solitary urochordate Styela plicata.

The mode of allorecognition in Styela plicata was determined by establishing reciprocal first-set allografts within pairs of individuals: 27% of pairs exhibited unilateral rejection where one animal retained reciprocal grafts while the other rejected them. This frequency was far greater than the expected level of chance elimination based on control autograft loss. Futhermore, second-set grafting confirmed the compatibility allocations of all unilaterally rejected pairs. The appearance of unilateral rejection is consistent with an allorecognition mechanism involving the specific identification of foreignness. Such systems are common among vertebrates, where a difference between individuals of a single tissue haplotype is sufficient to initiate allograft rejection. However, these results conflict with recognition systems operative in other invertebrates, where a single shared haplotype yields graft compatibility.

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PubMed1987

Cellular basis of allograft rejection in the solitary urochordate, Styela plicata.

The response of various cell types to first-set and secondary allografts in S. plicata was tested. The data implicate lymphocyte-like cells in allograft rejection. They were the only cells to specifically invade incompatible allografts and the surrounding tissue prior to rejection. This influx coincided with the destruction of other cells within allografts and thus may have been responsible for graft loss. Other cell types did, however, undertake non-specific responses to grafts which were probably stimulated by wounding. These results are discussed in terms of the evolution of the vertebrate immune system.

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PubMed1987

Allograft rejection and alloimmune memory in the solitary urochordate, Styela plicata.

The responses of the solitary urochordate, Styela plicata, to first- and second-set tunic grafts confirm the existence of a sensitive histocompatibility system. Most first-set allografts were eliminated (median rejection time, RT50, of 38.2 +/- 5.9 days) whereas the majority of autografts remained viable. Allograft rejection exhibited significant memory with second-set allografts being lost far more rapidly (RT50 = 22.0 +/- 2.6 days) than first-set allografts. This alloimmune memory was shown to survive for up to 50 days after first-set rejection. Furthermore, 3rd party grafting indicated that memory was specific to the presensitizing tissue type. These results are discussed in terms of the evolution of vertebrate immunity.

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PubMedDate not supplied

A humoral opsonin from the solitary urochordate Styela clava.

Opsonins play a key role in invertebrate humoral immune systems. An opsonin for yeast was identified in the plasma of the tunicate, Styela clava. In vitro cultures of hemocytes with homologous plasma-incubated yeast exhibited significantly higher levels of phagocytosis than controls. Studies indicated that the opsonic activity of Styela clava plasma increased the overall capacity for phagocytosis. Opsonization was inhibited by the carbohydrates mannan, N-acetyl-D-galactosamine, and galactose, and by the divalent cation chelator, EDTA. These data suggest that the Styela clava opsonin may share some functional similarities with a C-type lectin. Incubation of yeast with Styela clava and Styela plicata plasma prior to phagocytosis by hemocytes from both species indicated the Styela clava opsonin is species specific.

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PubMedDate not supplied

Cytotoxicity reactions in the solitary tunicate Styela plicata.

Hemocytes from the tunicate, Styela plicata, undertake cytotoxic responses toward human K562 tumor cells or rabbit red blood cells (RRBC). Reactions to both target cell types were found to require metabolic activity. However, it was not determined whether killing involves soluble factors or direct cell/cell contact. Differences in the response to varied effector:target ratios indicate that reactions against the K562 cells and RRBC are mediated by separate mechanisms. The existence of two discrete cytotoxic mechanisms was supported by experiments which demonstrated that pharmacological treatments have different effects on the cytotoxic destruction of K562 cells and RRBC. Moreover, cytotoxic reactions toward the different targets cells were shown to be mediated by different hemocyte sub-populations isolated from hemolymph by density gradient centrifugation.

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PubMedDate not supplied

Humoral opsonins of the tunicate, Pyura stolonifera.

This study characterizes humoral opsonins from the tunicate, Pyura stolonifera. The predominant opsonic components in P. stolonifera hemolymph were found to be calcium-dependent lectins with broad carbohydrate specificities. The opsonic lectins were purified by carbohydrate affinity chromatography which eluted a complex pattern of proteins ranging in molecular mass from 80 to >200kDa. Reducing and two dimensional SDS-PAGE indicated that the diversity of mature lectins evident under non-reducing conditions resulted from the differential oligomerization of two polypeptide sub-units (35 and 22kDa). In addition to lectin-mediated opsonic activity, hemolymph was also found to contain proteolytically activated opsonins. These data suggest that multiple, possibly interactive opsonic systems co-exist in P. stolonifera.

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PubMedDate not supplied

Chemotactic responses of hagfish (Vertebrata, Agnatha) leucocytes.

The chemotactic responses of hagfish leucocytes were tested using a variety of chemoattractants. Leucocyte migration was significantly enhanced by purified mammalian complement anaphylotoxin (C5a) and LPS-activated hagfish plasma. Checkerboard analyses confirmed that the responses of leucocytes to both of these chemoattractants were directed along concentration gradients (chemotaxis) and did not result from accelerated random movement (chemokinesis). Chemotaxis was undertaken by leucocyte fractions that were enriched in granulocytes, the predominant phagocytic cells of hagfish. The data suggest that chemotactic mechanisms may have been conserved during evolution to such a degree that mammalian chemoattractants can bind and activate chemotactic receptors on hagfish leucocytes. Moreover, hagfish appear to express plasma proteins that are structurally and functionally homologous to mammalian complement anaphylotoxins.

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