The possible role of the properdin system in transplantable cancer; the effect of zymosan on transplantable human carcinoma.

In a previous paper on heterologous trans plantation of tumors, we (2) reported successful growth and serial propagation of a carcinoma of the human colon in irradiated and cortisonetreated weanling Wistar rats. The fact that 205 other malignant tumors failed to grow simply served to emphasize the well known presence of a highly effective protective mechanism normally possessed by animals against all such transplanted foreign tissues. In attempting to explain this mech anism, we suggested that the properdin system might play a leading role in this resistance phe nomenon. The theoretical implication of the properdin system in the protective mechanism against heterologously transplanted tumors was based on three important discoveries. The first discovery was the role of lymphocytes in maintaining the defenses of the host against foreign tissues. As early as 1914, Murphy (6) was able to break down the animal defenses by destroying lymphocytes with irradiation or benzol. In 1949, Toolan and Kidd (13) demonstrated invasion of transplanted C3H mammary carcinoma and lymphosarcoma 6C3HED grown in A strain mice by lymphocytes with subsequent necrobiosis and disappearance of neoplastic cells. In 1951, by treating host animals with cortisone and thus destroying lymphocytes, Howes (3) was able to grow adenocarcinoma E 0771 and 775 in resistant C57BL mice, and Foley and Silverstein (1) succeeded in growing lymphosarcoma 6C3HED in resistant CFi mice. Using the irradiation technic of Murphy, Toolan (12) in 1951 succeeded, for the first time, in propa gating malignant human tumors in the subcutane ous tissues of laboratory animals. Thus, while it was quite apparent that lymphocytes were con cerned in maintaining resistance against heterolo gous tumors and that irradiation destroyed both the lymphocytes and the resistance, the precise