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Salmonella induces PD-L1 expression in B cells
Marcela Lopez-Medina1, Araceli Perez-Lopez2, Celia Alpuche-Aranda3
1Departamento de Biomedicina Molecular Centro de Investigación y Estudios Avanzados del IPN, México City CP 07360, Mexico.
Immunology Letters
|August 21, 2015
Summary
Salmonella persists in B cells by evading CD8 T cell responses. Infected B cells present Salmonella antigens but express PD-L1, potentially inhibiting T cell activity and enabling bacterial reservoirs.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Salmonella is known to persist within host cells, particularly B lymphocytes.
- The mechanisms by which Salmonella-infected B cells evade cytotoxic CD8 T cell responses remain poorly understood.
Purpose of the Study:
- To investigate how Salmonella-infected B cells avoid effector CD8 T cell responses.
- To characterize the antigen processing and presentation capabilities of Salmonella-infected B cells.
- To explore the role of co-stimulatory and inhibitory molecules in the context of Salmonella infection in B cells.
Main Methods:
- Infection of B cells (B1 and B2 subpopulations) with a Salmonella typhimurium strain engineered to express an ovalbumin peptide (SIINFEKL).
- Analysis of antigen processing and presentation via MHC class I K(b)-restricted molecules.
- Assessment of co-stimulatory (CD40, CD80, CD86) and inhibitory (PD-L1) molecule expression on infected B cells.
Main Results:
- Salmonella was shown to infect and survive in all B cell subpopulations.
- Infected B cells were capable of cross-presenting Salmonella antigens via MHC class I molecules, processed through both proteasomal and vacuolar pathways.
- Salmonella-infected B cells upregulated co-stimulatory molecules (CD40, CD80, CD86) and the inhibitory molecule PD-L1.
Conclusions:
- Infected B cells can prime and activate CD8(+) T cells through cross-presentation of Salmonella antigens.
- The upregulation of PD-L1 on Salmonella-infected B cells suggests a mechanism for immune evasion, potentially through the PD-1/PD-L1 pathway.
- This immune evasion likely contributes to persistent Salmonella infection by allowing B cells to act as bacterial reservoirs.
