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Monocyte rescue of human T cells from apoptosis is CD40/CD154 dependent
Abstract:
The induction of T-cell apoptosis is regulated in part by monocytes (CD14+ cells). Human peripheral blood monocytes inhibited the spontaneous cell death of activated T cells in vitro. The inhibition of T-cell apoptosis did not require autologous monocytes. Inhibition required direct contact with monocytes and was not due to a soluble factor. Furthermore, treatment of monocytes with actinomycin D, cycloheximide and paraformaldehyde abrogated the anti-apoptotic activity of these cells. Blocking antibody to CD40 and CD154 (CD40 ligand) decreased the ability of monocytes to aid in T-cell survival, whereas, blocking LFA-1/I-CAM-1, Fas ligand and the CD4/major histocompatibility complex class II interaction did not affect the influence of monocytes on T-cell survival. This shows that monocytes rescue of activated T cells from apoptosis is dependent upon CD40/CD154 interaction.
Insights
Monocytes (CD14+ cells) prevent T-cell apoptosis through direct contact, independent of soluble factors. This T-cell survival mechanism relies on the CD40/CD154 interaction, highlighting a key regulatory pathway in immune responses.
Area of Science:
- Immunology
- Cell Biology
Background:
- T-cell apoptosis is crucial for immune homeostasis and preventing autoimmunity.
- Monocytes play a regulatory role in immune responses, but their specific function in T-cell survival is not fully understood.
Purpose of the Study:
- To investigate the role of human peripheral blood monocytes in regulating T-cell apoptosis.
- To elucidate the mechanisms by which monocytes influence T-cell survival, focusing on cell contact and molecular interactions.
Main Methods:
- Human peripheral blood T-cells and monocytes (CD14+ cells) were co-cultured in vitro.
- Monocytes were treated with actinomycin D, cycloheximide, and paraformaldehyde to assess the requirement for active monocyte function.
- Blocking antibodies against CD40, CD154 (CD40 ligand), LFA-1/I-CAM-1, Fas ligand, and CD4/MHC class II were used to identify key molecular interactions.
Main Results:
- Monocytes inhibited spontaneous T-cell apoptosis in a contact-dependent manner, not mediated by soluble factors.
- Inhibition of T-cell apoptosis by monocytes was abrogated by treatments that disrupt monocyte function (actinomycin D, cycloheximide, paraformaldehyde).
- Blocking the CD40/CD154 (CD40 ligand) interaction significantly reduced the ability of monocytes to promote T-cell survival, while other tested interactions had no effect.
Conclusions:
- Monocytes actively rescue activated T cells from apoptosis through direct cell-cell contact.
- The CD40/CD154 (CD40 ligand) pathway is essential for the anti-apoptotic effect of monocytes on T cells.
- These findings reveal a critical mechanism of T-cell survival regulation mediated by monocyte-T cell interactions via CD40/CD154.