Overview of immunoevolution

Lipopolysaccharide-dependent induction of leech leukocytes that cross-react with vertebrate cellular differentiation markers

We have designed experiments to characterise leech leukocytes that mediate inflammatory responses. Shortly after inflicting injury to the body wall in the presence of lipopolysaccharides, many cells resembling macrophages, NK cells and granulocytes of vertebrates and many invertebrates migrated to the lesioned area. Nuclei of migrating cells incorporated bromodeoxyuridine. Using human monoclonal antibodies, macrophage-like cells were positive for CD25, CD14, CD61, CD68, CD11b and CD11c. NK-like cells were positive for CD25, CD56, CD57 and CD16, and granulocytes were positive for CD11b and CD11c. In blots of leech extracts, the CD25 monoclonal antibody recognised a band of about 55 kD; the CD56 monoclonal antibody, two bands of about 140 and 210 kD; the CD57 monoclonal antibody, two bands of about 106 and 70 kD; the CD14 monoclonal antibody, a band of about 50 kD; the CD16 monoclonal antibody, a band of about 60 kD. CD61 and CD68 both recognised a band of about 110 kD; CD11b recognised a band of 200 kD, and CD11c, a band of 180 kD.

The effects of copper on actin and fibronectin organization in Mytilus galloprovincialis haemocytes

The effects of copper on actin and fibronectin organization in Mytilus galloprovincialis haemocytes were studied. The Cu2+ exposure of mussels caused severe perturbations in haemocyte actin and fibronectin organization with respect to non-exposed organisms. Cytoskeletal actin was analysed by indirect immunofluorescence, using an antitotal actin monoclonal antibody, and by rhodamine-conjugated phalloidin. The majority of haemocytes from Cu(2+)-exposed mussels displayed a round morphology, with short and blunt filopodia; they lacked the polarized phenotype which was typical in control samples. The cytoskeleton alteration, more evident after phalloidin staining, resulted in the disappearance of filamentous actin. The actin cortical meshwork also appeared disorganized. The cytoskeletal morphology studied by transmission electron microscopy after negative staining of Triton X-100-treated haemocytes confirmed these observations. The structural organization of actin when analysed by Western blotting showed a larger number of Triton-soluble actin pools in treated mussel haemocytes. Fibronectin was studied by indirect immunofluorescence using a polyclonal antiserum directed against mussel fibronectin. In treated mussels, fibronectin appeared to be strongly disorganized and its levels decreased in both haemocytes and haemolymph. The mechanism(s) of the copper-induced alterations on actin and fibronectin organization in mussel immunocytes is discussed.

Characterization and immunocytochemical localization of actin and fibronectin in haemocytes of the mussel Mytilus galloprovincialis

Cell-extracellular matrix interactions are recognized to be important for human leucocyte functions, including chemotaxis and phagocytosis. These activities depend on a reorganization of the microfilament actin (F-actin) promoted by fibronectin, one of the major components of extracellular matrices. Although invertebrate haemocytes are, in many aspects, similar to the human granulocyte-monocyte-macrophage cell lineage, actin and fibronectin have not been well studied in these cells. Consequently, the characterization and structural organization of actin and fibronectin in mussel (Mytilus galloprovincialis) haemocytes was investigated using Western blotting analysis, indirect immunofluorescence and immunoelectron microscopy. Actin was immunocharacterized by an anti-total actin monoclonal antibody. Fibronectin was immunocharacterized by an autologous polyclonal antiserum directed against the protein of mussel haemolymph. Actin was mainly localized along the peripheral cytoplasm of the haemocyte. The distribution of the F-actin microfilaments was assayed with Rhodamine-labelled phalloidin. F-actin was associated mainly with stress-fibres of spreading haemocytes and with microspikes at the adhesion sites. The labelling by the anti-fibronectin antiserum of the haemocyte rough endoplasmic reticulum vesicles, revealed by immunoelectron microscopy, suggests that these cells are involved in fibronectin biosynthesis. Gold particles were also present along the outer surfaces of the cell plasma membrane and its protrusions. Mussel fibronectin was localized immunohistochemically at the adhesion sites and in the extracellular matrix fibrils. The relationships between fibronectin and the actin cytoskeleton in Mytilus galloprovincialis haemocytes are discussed.