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T cell suppressor factor from human glioblastoma cells is a 12.5-kd protein closely related to transforming growth
Abstract:
T cell suppressor factor produced by human glioblastoma cells inhibits T cell proliferation in vitro and more specifically interferes with interleukin-2 (IL-2)-dependent T cell growth. Here we report the purification of this factor from conditioned medium of the human glioblastoma cell line 308. Amino-terminal sequence analysis of the 12.5-kd protein demonstrates that eight out of the first 20 amino acids are identical to human transforming growth factor-beta. Purified glioblastoma-derived T cell suppressor factor and transforming growth factor-beta from porcine platelets inhibit both IL-2-induced proliferation of ovalbumin-specific T helper cells and lectin-induced thymocyte proliferation with similar specific activities. If released by glioblastoma cells in vivo, the factor may contribute to impaired immunosurveillance and to the cellular immunodeficiency state detected in the patients.
Insights
Human glioblastoma cells produce a T cell suppressor factor that inhibits T cell proliferation, particularly interleukin-2 (IL-2)-dependent growth. This factor is identified as transforming growth factor-beta (TGF-β), potentially impairing immune responses in patients.
Area of Science:
- Immunology
- Oncology
- Molecular Biology
Background:
- Glioblastoma cells produce factors that suppress T cell activity.
- This suppression impacts the immune system's ability to fight tumors.
- Understanding these factors is crucial for cancer immunotherapy.
Purpose of the Study:
- To purify and characterize the T cell suppressor factor from human glioblastoma cells.
- To determine the identity of the suppressor factor.
- To assess its functional similarity to known immunosuppressive molecules.
Main Methods:
- Purification of the suppressor factor from conditioned medium of glioblastoma cell line 308.
- Amino-terminal sequence analysis of the purified protein.
- In vitro assays measuring inhibition of T cell proliferation, specifically IL-2-dependent growth and thymocyte proliferation.
Main Results:
- A 12.5-kd protein was purified and identified as glioblastoma-derived T cell suppressor factor.
- Amino-terminal sequencing revealed significant identity to human transforming growth factor-beta (TGF-β).
- Purified glioblastoma TGF-β and platelet-derived TGF-β exhibited similar inhibitory activity on T cell proliferation.
Conclusions:
- Glioblastoma-derived T cell suppressor factor is TGF-β.
- TGF-β produced by glioblastoma cells may contribute to immune evasion in patients.
- This finding suggests a mechanism for the impaired immunosurveillance observed in glioblastoma patients.