Lysozyme enhancement of tumor cell immunoprotection in a murine fibrosarcoma

We examined the ability of human lysozyme (HLZM) to enhance the immunogenicity of a methylcholanthrene-induced murine fibrosarcoma of C57BL/10 mice. Following s.c. injection of 10(4) live tumor cells, 100% of mice developed palpable tumors within 16 +/- 3 (S.D.) days. Prechallenge immunization with 10(6) irradiated tumor cells with or without complete Freund's adjuvant resulted in protection from tumor development in 14 and 22% of mice, respectively. Incubation of tumor cells with HLZM prior to immunization approximately doubled the degree of protection, with 42 to 44% of mice remaining free of tumor. This enhanced protection was dependent on the enzymatic activity of HLZM. These data suggest that HLZM enhances tumor cell immunogenicity in this model.