Transplantation immunity in mollusks: The histoincompatibility of Helisoma duryi normale with allografts and xenografts

Abstract

Digestive gland tissues from the gastropods Helisoma duryi normale (strain HI-3), Helisoma trivolvis, Tarebia granifera, and Melania newcombi were transplanted into the cephalopedal sinuses of H. duryi normale (strain HI-2), and their fates were traced by examining histological sections fixed at 24, 48, 96, 192, and 384 hr post-transplantation. It was apparent that the recipients were capable of differentiating between allografts and xenografts since host reactions directed at the latter were more rapid and generally more severe. The rapid dissociation of the acinar cells of transplanted H. trivolvis and T. granifera suggested that some yet undetermined factor of host origin may be responsible for the lysis of these xenogenic tissues within 24 hr. Cellular capsules surrounding the dissociated cells of H. trivolvis and T. granifera transplants were in the form of hypertrophic fibroblasts and epithelioid cells. Evidences indicated that the latter differentiated from the former which, in turn, had differentiated from wandering leukocytes. Both H. trivolvis and T. granifera cells were encapsulated by the 48th hour. Eventually, the cellular remnants of these were removed by leukocytic phagocytosis. In the case of M. newcombi xenografts, the primary type of host reaction was in the form of myofibrous encapsulation, which was initiated by the 24th hour. Multinucleate macrophages were also associated with these xenografts at the same time. The transplants, however, were not dissociated during the span of the experiment. In the case of H. duryi normale allografts, epithelioid cell encapsulation occurred by the 192nd hour but the acini were still not dissociated by the 394th hour.