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20alpha-hydroxysteroid dehydrogenase: a T lymphocyte-associated enzyme.
Journal of Immunology (Baltimore, Md. : 1950)
|October 1, 1977
Summary
20alpha-Hydroxysteroid dehydrogenase (20alpha-SDH) is linked to T lymphocytes and its activity varies with age and T cell stimulation. This enzyme may protect developing thymocytes from progesterone.
Area of Science:
- Immunology
- Enzymology
- Steroid Metabolism
Background:
- 20alpha-Hydroxysteroid dehydrogenase (20alpha-SDH) is an enzyme involved in progesterone metabolism.
- The role and localization of 20alpha-SDH within the immune system, particularly in T lymphocytes, are not well understood.
- Understanding steroid metabolism in immune cells is crucial for comprehending immune regulation.
Purpose of the Study:
- To investigate the association of 20alpha-SDH with T lymphocytes.
- To characterize the activity and regulation of 20alpha-SDH in immune cells.
- To explore the potential role of 20alpha-SDH in thymocyte proliferation and progesterone's effects.
Main Methods:
- Enzyme activity assays were performed on various mouse immune cell populations (spleen, thymus, bone marrow).
- Flow cytometry was used to identify T lymphocyte populations (theta antigen, nylon wool adherence).
- Cell cultures were treated with T cell mitogens (PHA, Con A) and B cell mitogen (LPS) to assess enzyme induction.
- Age-dependent activity levels were measured in thymocytes, spleen cells, and lymph node lymphocytes.
- Effects of progesterone and 20alpha-dihydroprogesterone on mitogen-stimulated thymocyte proliferation were assessed.
Main Results:
- 20alpha-SDH activity was predominantly found in T lymphocyte-enriched populations, including thymocytes and spleen cells bearing theta antigen.
- Enzymatic activity was significantly lower in bone marrow cells and in spleen cells from neonatally thymectomized or athymic nude mice.
- T cell mitogens, but not B cell mitogens, induced high levels of 20alpha-SDH activity.
- Enzyme activity was highest in 4-week-old mice and decreased with age.
- Progesterone inhibited thymocyte proliferation, while its metabolite 20alpha-dihydroprogesterone did not.
Conclusions:
- 20alpha-SDH is strongly associated with T lymphocytes and its expression is regulated by T cell activation.
- The age-dependent activity suggests a role in immune development or maturation.
- 20alpha-SDH may play a protective role by metabolizing progesterone, thereby preventing its inhibitory effects on embryonic thymocyte proliferation.