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Antigen-specific purification of blocking factors from sera of mice with chemically induced tumors
Abstract:
Serum from mice with growing tumors can prevent ("block") the destruction of tumor cells by immune lymphocytes, as measured in a microcytotoxicity assay. Factors responsible for this blocking activity were purified by binding to immune adsorbents that had been prepared from antibodies obtained by immunizing BALB/c mice to the homologous tumors. Two transplantable BALB/c sarcoma lines with individually different tumor-specific transplantation antigens were studied in parallel. The original tumor-specific blocking activity was recovered by elution of the immune adsorbents; that is, (i) eluates blocked the reduction of surviving tumor cell targets by immune lymphocytes only if the tumor specificity, and (ii) immune adsorbent columns prepared from tumor-immune sera recognized the purified blocking fractions in a tumor-specific fashion, indicating that a portion of the humoral response in the immune mice was directed against a factor that was individually distinct for each tumor. Absorption of eluates with the homologous tumor cells removed their blocking activity, indicating that the blocking factors have antigen-binding properties. Blocking activity in the purified fractions resided in molecules presumptively identified as glycoproteins by affinity chromatography on concanavalin A-Sepharose.
Insights
Tumor-specific blocking factors in mouse serum prevent immune cell destruction of cancer cells. These factors, identified as glycoproteins, bind to tumor antigens, highlighting a distinct humoral response in tumor immunity.
Area of Science:
- Immunology
- Oncology
- Biochemistry
Background:
- Serum from tumor-bearing mice can inhibit immune-mediated tumor cell lysis.
- This blocking activity is crucial for understanding tumor immune evasion strategies.
Purpose of the Study:
- To purify and characterize the factors responsible for blocking activity in mouse serum.
- To investigate the tumor-specific nature of these blocking factors.
Main Methods:
- Immune adsorbent purification using antibodies against tumor-specific antigens.
- Microcytotoxicity assays to measure blocking activity.
- Affinity chromatography with Concanavalin A-Sepharose for glycoprotein identification.
Main Results:
- Purified factors exhibited tumor-specific blocking activity.
- Blocking factors demonstrated antigen-binding properties after absorption with tumor cells.
- The blocking molecules were identified as glycoproteins.
Conclusions:
- A portion of the humoral immune response targets tumor-specific factors.
- These blocking factors, likely glycoproteins, play a role in tumor immune evasion by binding to tumor antigens.