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Cyclic AMP inhibits macrophage suppressor function and enhances lymphocyte proliferation
W M Gonsalkorale1, M J Dascombe, I V Hutchinson
1School of Biological Sciences, University of Manchester, U.K.
Immunology
|December 1, 1993
Summary
Increasing cyclic AMP (cAMP) activity enhances rat lymphocyte proliferation in spleen mixed lymphocyte reactions (MLR) by suppressing inhibitory macrophages. This contrasts with lymph node MLR, where cAMP reduces proliferation.
Area of Science:
- Immunology
- Cellular Biology
- Pharmacology
Background:
- Cyclic AMP (cAMP) is a crucial second messenger involved in regulating immune cell function.
- The mixed lymphocyte reaction (MLR) is a model for T-cell mediated immune responses, often influenced by accessory cells like macrophages.
Purpose of the Study:
- To investigate the impact of elevated cyclic AMP (cAMP) levels on lymphocyte proliferation within the rat mixed lymphocyte reaction (MLR).
- To elucidate the role of macrophages in mediating the effects of cAMP on MLR proliferation.
Main Methods:
- Rats underwent mixed lymphocyte reactions (MLR) using either lymph node (LN) or spleen cells.
- Cells were treated with varying concentrations of dibutyryl cAMP (dbcAMP) or prostaglandin E2 (PGE2).
- Macrophage depletion and addition experiments were conducted to assess their role in MLR modulation.
Main Results:
- Dibutyryl cAMP (dbcAMP) and prostaglandin E2 (PGE2) dose-dependently reduced proliferation in the lymph node (LN) MLR.
- Conversely, lower concentrations of dbcAMP and PGE2 significantly increased proliferation in the spleen MLR.
- The proliferative enhancement in the spleen MLR was dependent on the presence of macrophages and was abolished by macrophage depletion.
Conclusions:
- Cyclic AMP (cAMP) enhances lymphocyte proliferation in the rat spleen MLR, primarily through the suppression of inhibitory macrophage activity.
- These findings suggest a context-dependent role for cAMP in regulating immune responses, with macrophages acting as key modulators in the spleen environment.