Studies on the endotoxin induced tumor resistance

Area of Science:

• Immunology
• Tumor Biology
• Microbiology

Background:

• Nonspecific resistance to tumors can be modulated by microbial products.
• Endotoxins, such as lipopolysaccharide (LPS), are known to possess immunomodulatory properties.

Purpose of the Study:

• To investigate the immunologic mechanisms underlying endotoxin-mediated enhancement of tumor resistance (TUR).
• To identify the structural components of endotoxin responsible for enhancing TUR.
• To elucidate the cellular and molecular mediators involved in LPS-induced antitumor effects.

Main Methods:

• Comparison of various LPS, endotoxic glycolipids, and polysaccharide (PS) preparations for their ability to enhance TUR.
• Assessment of cellular involvement (B cells, macrophages, T cells) in the LPS-mediated enhancement.
• Analysis of soluble factors in serum mediating antitumor activity.

Main Results:

• Optimal tumor protection was observed with LPS pretreatment at the tumor challenge site.
• Intact LPS and some glycolipids enhanced TUR, while some endotoxic glycolipids were inactive despite toxicity.
• Lipid-free PS preparations showed partial activity.
• Evidence suggests involvement of B cells and macrophages, but not T cells.
• LPS/PS induced soluble serum factors that transferred antitumor effects.
• BCG preinfection potentiated LPS/PS-induced antitumor activity.

Conclusions:

• Endotoxin structural components, particularly intact LPS and certain glycolipids, are crucial for enhancing tumor resistance.
• The mechanism involves B cells, macrophages, and soluble serum factors, independent of T cells.
• BCG infection can augment endotoxin's ability to induce antitumor responses.