TPA, tumor promoter-induced suppression of immunoglobulin secretion in human blood lymphocytes
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Abstract:
12-O-Tetradecanoylphorbol-13-acetate (TPA) modulates DNA synthesis and differentiation of normal and malignant human lymphoid cells. Using the reverse plaque forming assay and radioimmunoassay, we showed that nontoxic concentrations of TPA (5 to 10 ng/ml) inhibited Ig secretion of peripheral blood lymphocytes. This inhibition was dependent on T lymphocytes and not monocytes; TPA treatment of the B cell-enriched fraction slightly enhanced Ig secretion. Suppression was evident when the proportion of TPA-pretreated T lymphocytes exceeded 50%. TPA-induced suppressor cells were present in both OKT8+ (suppressor/cytotoxic) and OKT4+ ("helper/inducer") subpopulations. The suppression was diminished but not abolished by the irradiation of T lymphocytes. In addition, TPA treatment modulated the expression of OKT4 antigen, whereas the expression of OKT8, 9.6 (sheep erythrocyte receptors) and surface Ig remained unchanged. Modulation of OKT4 was energy dependent and was not blocked by a maximal saturation of TPA receptors at 4 degrees C. We postulate that TPA-induced suppression of Ig secretion is T cell dependent and is likely to be associated with proliferation and activation of OKT8+ and OKT4+ lymphocytes and the induction of OKT4+ suppressor cells.
Insights
12-O-Tetradecanoylphorbol-13-acetate (TPA) inhibits immunoglobulin (Ig) secretion in human lymphocytes by activating T cells. This TPA-induced suppression involves both helper and suppressor T cell subsets, impacting immune responses.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- 12-O-Tetradecanoylphorbol-13-acetate (TPA) is known to modulate DNA synthesis and differentiation in human lymphoid cells.
- Understanding the effects of TPA on immune cell function is crucial for comprehending immune regulation.
Purpose of the Study:
- To investigate the impact of TPA on immunoglobulin (Ig) secretion by human peripheral blood lymphocytes.
- To determine the cellular mechanisms and T cell subset involvement in TPA-mediated immune modulation.
Main Methods:
- Reverse plaque forming assay and radioimmunoassay were employed to measure Ig secretion.
- Flow cytometry was used to analyze T cell subpopulations (OKT4+, OKT8+) and antigen expression.
- Experiments included T cell enrichment, monocyte depletion, and lymphocyte irradiation.
Main Results:
- Nontoxic concentrations of TPA (5-10 ng/ml) significantly inhibited Ig secretion.
- TPA-induced suppression was T cell-dependent, not mediated by monocytes.
- Suppression was observed with TPA-treated T lymphocytes exceeding 50% and involved both OKT4+ and OKT8+ subpopulations.
- TPA modulated OKT4 antigen expression in an energy-dependent manner.
Conclusions:
- TPA induces suppression of Ig secretion in a T cell-dependent manner.
- The findings suggest proliferation and activation of specific T cell subsets (OKT4+ and OKT8+) contribute to TPA-mediated suppression.
- TPA's modulation of T cell surface antigens, particularly OKT4, plays a role in regulating immune responses.