Disruption of CD154:CD40 blocks generation of allograft immunity without affecting APC activation
1Department of Environmental and Molecular Toxicology, Environmental Health Sciences Center, Oregon State University, Corvallis 97331, USA.
Insights
The CD154-CD40 pathway is crucial for allograft immunity, impacting T cell priming and responses. However, this interaction is not the primary driver for activating antigen-presenting cells (APCs).
Area of Science:
- Immunology
- Transplantation immunology
Background:
- The CD154 (CD40 ligand) and CD40 interaction is vital for adaptive immunity.
- CD40 ligation on antigen-presenting cells (APCs) is thought to enhance their function, including costimulatory molecule expression and IL-12 production.
Purpose of the Study:
- To investigate the role of the CD154-CD40 pathway in a murine model of allograft rejection.
- To determine if CD154-CD40 interaction is essential for APC activation in the context of allograft immunity.
Main Methods:
- Utilized CD154 knockout mice and anti-CD154 mAb treatment in an allograft rejection model.
- Assessed cytotoxic T lymphocyte (CTL) and alloantibody responses.
- Measured splenic cytokine production (IL-2, IFN-gamma, TNF) and APC costimulatory molecule (CD86) expression.
- Administered agonistic anti-CD40 mAb and B7-transfected tumor cells to evaluate functional restoration.
Main Results:
- CD154 knockout mice and anti-CD154 treated mice showed severely compromised CTL and alloantibody responses.
- Splenic cytokine production was significantly suppressed in CD154-deficient mice, indicating impaired T cell priming.
- APCs from CD154 knockout mice exhibited comparable CD86 expression and IL-12 production to wild-type controls.
- Restoration of APC function via anti-CD40 mAb or B7 transfection did not restore allograft immunity in CD154-deficient mice.
Conclusions:
- The CD154-CD40 pathway is essential for generating allograft immunity, particularly for T cell priming.
- APC activation, as measured by CD86 and IL-12, is not primarily dependent on the CD154-CD40 interaction.
- The study highlights a critical role for CD154-CD40 in adaptive immunity beyond APC activation.
Abstract:
CD154 (CD40 ligand, gp39) interaction with its receptor CD40 has been shown to be critically important for the generation of cell-mediated as well as humoral immunity. It has been proposed that ligation of CD40 on APCs, presumably by activated Th cells, leads to increased APC function as defined by up-regulation of costimulatory molecules and enhancement of IL-12 production. In this report, we directly examined the contribution of the CD154:CD40 pathway in a murine model of allograft rejection. Generation of both the CTL and alloantibody responses following injection with allogeneic P815 tumor cells was severely compromised in CD154 knockout mice and wild-type C57BL/6 mice treated with the anti-CD154 mAb, MR1. Splenic production of IL-2, IFN-gamma, and TNF was significantly suppressed from CD154-deficient mice, indicating a lack of T cell priming. However, splenic cells from CD154 knockout mice induced comparable levels of CD86 expression and IL-12 production when compared with their wild-type littermates. The treatment of CD154-/- mice with the agonistic anti-CD40 mAb, FGK45, generated activated APCs yet failed to restore either the CTL or alloantibody responses to P815. Likewise, immunization with B7-transfected P815 tumor cells failed to generate expansion of the CTL effector population in CD154-/- mice. These results suggest that the generation of allograft immunity is dependent on the interaction of CD154 with CD40 but not primarily for the activation of APCs.
