Decrease of transplantability by the immunopotentiators, OK-432 and interleukin-2: experiments on a human hepatoma...

Area of Science:

• Immunology
• Oncology
• Cancer Research

Background:

• Nonspecific cytotoxic activity of spleen cells is crucial for tumor resistance.
• Understanding the role of these cells in hepatoma graft challenges is important.

Purpose of the Study:

• To investigate the relationship between spleen cell cytotoxicity and resistance to human hepatoma cell line (HCC-M) grafts in nude mice.
• To determine the role of natural killer cells and other cytotoxic cells in this process.

Main Methods:

• Administration of immunopotentiators (OK-432 or human interleukin-2) prior to HCC-M cell inoculation.
• Assessment of tumor development (tumor take rate and size).
• Evaluation of spleen cell cytotoxicity against YAC-1 or HCC-M targets.
• Inhibition studies using anti-asialo GM1 (ASGM1) antiserum and in vitro treatment.

Main Results:

• Immunopotentiators significantly inhibited tumor development.
• The inhibitory effect was abrogated by anti-ASGM1 antiserum, indicating the involvement of ASGM1+ cells.
• A significant inverse correlation was observed between tumor volume and spleen cell cytotoxicity.
• Enhanced cytotoxicity involved heterogeneous cells, including ASGM1+ natural killer cells and other non-specific cytotoxic cells.

Conclusions:

• Nonspecific cytotoxic cells play a critical role in resistance against tumor cell challenge.
• The level of cytotoxic activity at the time of tumor cell challenge is a key determinant of tumor development.
• Immunopotentiators can enhance this resistance through modulation of non-specific cytotoxic cells.