Reference: Biol Bull. 167: 238-250. (August, 1984) INFLAMMATORY-LIKE REACTION IN THE TUNIC OF CIONA INTESTINALIS (TUNICATA). II. CAPSULE COMPONENTS NICOLO PARRINELLO AND ELEONORA PATRICOLO Institute of Zoology, Palermo University, Via Archirafi, 18 90123 Palermo, Italy Abstract An inflammatory-like process is initiated in the tunic of Ciona intestinalis by particulate agents and soluble proteins. It includes the induction of a capsule in the form of a whitish disc in the tunic and which isolates injected materials. Histologically, the capsule structure shows a large number of cells collected around the injection wound. Vesicular cells release an unidentified amorphous substance which mixes with mucopolysaccharide and protein contents of typical "granule-packed cells" to form the capsule matrix. The vacuolated epithelial cells, lining the inner zone of the tunic, can release an unidentified substance which participates in matrix production. Lymphocyte-like cells can be present and transitional cells may differentiate into the vesicular cells. Large refringent granule cells, and compartment cells which can contain refringent material, were found inside the wound and are thought to release the glycoprotein substances. The degranulation of eosinophil granulocytes occurs in the same period. The capsule induced by soluble proteins lacks "granule-packed cells" while fine granular material, mucopolysaccharide in nature, is layered on the epithelium of the capsule. Observations of early stages of capsule formation show granular and hyaline amoebocytes, probably phagocytes, which quickly surround the foreign material {e.g., erythrocytes) followed by transitional cells and, finally, vesicular cells, which can form an incipient capsule within 24 hours. Encapsulation in Ciona intestinalis is a cellular response which includes the mechanisms for tunic production in order to isolate the inflamed tissue while the foreign material is disrupted and the injection wound repaired. Introduction In tunicates, encapsulation is a chronic inflammatory-like response which appears, in the body wall, to isolate natural invaders (Bresciana and Liitzen, 1960; Monniot, 1963; Dudley, 1968), experimentally inserted objects (Smith, 1970; Anderson, 1971), or bacteria (Thomas, 1931). Vacuolated blood cells, predominantly morula cells, are responsible for these reactions (Wright, 1981; Wright and Ermak, 1982). The ascidian, Ciona intestinalis, reacts by cellular responses toward foreign ma-terials inserted into the tunic (Wright and Cooper, 1975; Parrinello^/fl/., 1976, 1977). In previous papers we have shown that a capsule can envelop the particulate or soluble injected materials by cell infiltration and glycoprotein secretions (Parrinello et ai, 1976, 1977). In some specimens the response can induce local tissue damage which seems to be independent of encapsulation. The tunic injury depends on the dose and nature of the irritant, involves eosinophil granulocytes, and shows lysosomal content release by various degranulation mechanisms (Parrinello and De Leo, in prep.). Received 6 March 1984; accepted 29 May 1984. Abbreviations: SE = sheep erythrocytes; PBS = phosphate-buffered saline (0.01 M pH 7.4 phosphate buffer containing 0. 15 M NaCl); BSA = bovine serum albumin; He = Octopus vulgaris hemocyanin; Hb = bovine hemoglobin; PAS = periodic acid Schiff. 238
BioStor
