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Updated: Jun 6, 2026
Murine Model of CD40-activation of B cells
Published on: March 5, 2010
CD40L co-stimulation from CD8+ to CD4+ effector memory T cells supports CD4+ expansion
Maria Xydia1, Yingzi Ge, Ulrike Quitsch
1Translational Immunology Unit, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Insights
Direct interactions between CD4(+) and CD8(+) effector memory T cells (T(EM)) enhance immune responses. This study reveals CD40/CD40L signaling is crucial for bi-directional T(EM) expansion, vital for robust immunity.
Area of Science:
- Immunology
- Cellular Biology
Background:
- Effector memory T cells (T(EM)) are critical for adaptive immunity against infections.
- The mechanisms regulating T(EM) maintenance and proliferation remain incompletely understood.
Purpose of the Study:
- To investigate the role of direct cell-cell interactions between CD4(+) and CD8(+) T cells in human T(EM) expansion.
- To elucidate the molecular pathways involved in T(EM) proliferation.
Main Methods:
- Separated and mixed CD4(+) and CD8(+) T(EM) populations were cultured and stimulated in vitro.
- Flow cytometry was used to analyze cell proliferation and surface marker expression (e.g., CD40L, CD40).
- Blocking antibodies were employed to inhibit specific molecular interactions.
Main Results:
- Mixed CD4(+) and CD8(+) T(EM) populations exhibited significantly increased proliferation compared to isolated subsets.
- Co-activation induced reciprocal expression of CD40L and CD40 on both CD4(+) and CD8(+) T(EM).
- Blocking CD40L on either T cell subset impaired the proliferation of the other, demonstrating bi-directional signaling.
Conclusions:
- Direct, bi-directional CD40/CD40L interactions between CD4(+) and CD8(+) T(EM) cells are essential for efficient T(EM) expansion.
- These interactions facilitate robust immune memory and response to infection.
Abstract:
Effector memory T cells (T(EM)) have an important role in immunity against infection. However, little is known about the factors regulating T(EM) maintenance and proliferation. In this study, we investigated the role of direct interactions between CD4(+) and CD8(+) T cells (TC) for human T(EM) expansion. Proliferation of separated or mixed CD4(+) and CD8(+)T(EM) populations was analyzed after polyclonal stimulation in vitro. Compared to each isolated subset mixed T(EM) populations showed increased proliferation and expansion of both CD4(+) and CD8(+)T(EM) subpopulations. Combined activation of CD4(+) and CD8(+) memory T cells (Tmem) induced an increased expression of CD40L and CD40 on both populations. Subsequently, CD40/CD40L caused a bi-directional stimulation of CD40(+)CD4(+)T(EM) by CD40L(+)CD8(+)T(EM) and of CD40(+)CD8(+)T(EM) by CD40L(+)CD4(+)T(EM). Blocking of CD40L on activated CD8(+)T(EM) selectively inhibited proliferation of CD4(+)T(EM), while blocking of CD40L on CD4(+)T(EM) abrogated proliferation of CD8(+)T(EM). Taken together, we demonstrate for the first time that the expression of CD40L is exploited on the one hand by CD8(+)T(EM) to increase the proliferation of activated CD4(+)T(EM) and on the other hand by CD4(+)T(EM) to support the expansion of activated CD8(+)T(EM). Thus, efficient T(EM) expansion requires bi-directional interactions between CD4(+) and CD8(+)T(EM) cells.
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