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A Comparison between Granulomatosis and Lymphoreticular Neoplasia in Diemictylus viridescens and Xenopus laevis¹

Department of Biology, Reed College, Portland, Oregon 97202

Stocks of Xenopus laevis which have been used recently to generate lymphoreticular neoplasia (L-1) have apparently become infected with pathogenic acid-fast bacteria. These materials provided us with an unusual opportunity to compare a granulomatous response with this lymphoreticular neoplasm of the histiocytic type in both newt and Xenopus hosts. The granuloma foci were found to differ from those of the neoplasm with regard to their cellular composition (50% histiocytes, 50% polymorphonucleocytes), growth characteristics (enlargement by compression or distortion of neighboring normal tissues), and necrosis (caseating). In both host species, there appeared to be a subsequent increase in mitosis within granuloma nodules leading to an increase in histiocyte numbers, suggesting a transition to the histopathology of L-1. Acid-fast bacterial populations appeared to be brought under control eventually by phagocytosis as their numbers decreased with time. While previous studies showed no effect of thymectomy on L-1 development in Xenopus, granuloma formation increased considerably as compared with nonthymectomized controls. The use of 30,000 x g centrifugation of an L-1 tissue homogenate allowed for injection of a supernatant fluid which subsequently initiated neoplastic foci and demonstrated that granuloma development need not precede lymphoid neoplasia in the newt.

¹ Supported in part by USPHS Grant CA 08268 from the National Cancer Institute, NIH, Bethesda, Md.

Received 5/12/70. Accepted 7/ 2/70.