Damselfish with neurofibromatosis exhibit cytotoxicity toward tumor targets

Damselfish neurofibromatosis (DNF) is a malignant transmissible disease affecting Schwann cells, and is the only naturally occurring animal model of human neurofibromatosis type 1. The current study was designed to determine whether fish in the early stages of disease have measurable immune responses toward DNF tumor cells. Three DNF tumor cell lines were used as targets in standard 51Cr cytotoxic assays. In addition, Lutjanus griseus erythrocytes served as nonspecific targets, and concanavalon A (Con A) blasts from healthy animals served as normal target cells. Results of this study show that tumor-bearing damselfish have cells capable of destroying tumor targets but healthy animals display minimal, if any, reactivity toward the DNF tumor lines. The majority of antitumor activity resides in the spleen; the pronephros appears to contain the majority of nonspecific activity. Data also show that some of the effector cells are analogous to the nonspecific cytotoxic cells of catfish. No lysis of healthy damselfish targets was observed. Thus damselfish have cytotoxic cells capable of interacting with tumor targets, but in the majority of animals this response is not adequate to circumvent the process of tumorigenesis.