INFLAMMATORY-LIKE REACTION IN THE TUNIC OF CIONA INTESTINALIS (TUNICATA). II. CAPSULE COMPONENTS

¹ Institute of Zoology, Palermo University, Via Archirafi, 18 90123 Palermo, Italy

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.

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