Studies on the internal defense mechanisms of sponges: III. Cellular reactions in Terpios zeteki to implanted heterologous biological materials

Abstract

Cellular responses in Terpios zeteki to implanted heterologous biological materials consisting of human erythrocytes, trematode rediae and cercariae, and molluscau muscles, were examined at 6, 12, 24, and 48 hr postimplantation. It was determined that erythrocytes were either phagocytized or encapsulated by sponge archaeocytes and were gradually eliminated from the mesoglea via the migration of host cells into excurrent canals. The mesoglea was essentially free of implanted erythrocytes by the 48th hr. Implants of rediae only evoked slight encapsulation involving archaeocytes and collencytes, with some of the latter forming syncytia. Freed cercariae were enveloped by a relatively thick syncytial capsule of archaeocytes and collencytes. This capsule, however, disintegrated by the 48th hr when the cercarial tissues decomposed. Simultaneously, a large number of archaeocytes including amorphous materials, most probably fragments of disintegrated implanted tissues, were found in the lumina of excurrent canals. Response to muscle implants consisted primarily of an irregular distribution of collencytes and archaeocytes on the surfaces, but with no evidence of true capsule formation. Thus, incomplete or complete encapsulation of heterografts has been demonstrated in sponges for the first time. Incision sites in sponges of the control series revealed a gradual concentration of parenchymal cells along the cut surfaces. No fusion of these surfaces was observed.