Thymus-derived lymphocytes produce an immunologically specific macrophage-arming factor

Area of Science:

• Immunology
• Cancer Research
• Cell Biology

Background:

• Allogeneic tumor immunization can elicit immune responses.
• Spleen cells are key components of the adaptive immune system.
• Macrophage function is critical in anti-tumor immunity.

Purpose of the Study:

• To characterize a novel factor released by spleen cells upon tumor cell stimulation.
• To investigate the role of T-cells in the production of this factor.
• To determine the mechanism by which this factor enhances anti-tumor activity.

Main Methods:

• Immunization of mice with allogeneic tumor cells.
• Culture of immune spleen cells with specific tumor cells.
• Supernatant analysis for macrophage-arming factor (SMAF) activity.
• T-cell depletion studies using anti-theta serum and thymectomy.
• Molecular weight determination via column separation.

Main Results:

• A macrophage-arming factor (SMAF) was identified in spleen cell culture supernatants.
• SMAF non-specifically binds to macrophages, rendering them cytotoxic to specific tumor cells.
• SMAF-treated target cells are killed by normal macrophages.
• T-cells (thymus-derived cells) are essential for SMAF production.
• SMAF exhibits properties of a cytophilic antibody but has a molecular weight of 50,000-60,000 daltons, distinct from known immunoglobulins.

Conclusions:

• T-cells are indispensable for the generation of SMAF.
• SMAF represents a novel mechanism for enhancing macrophage-mediated anti-tumor cytotoxicity.
• SMAF's unique molecular weight suggests it is a non-immunoglobulin factor.