Salmonella induces PD-L1 expression in B cells.
Salmonella persists for a long time in B cells; however, the mechanism(s) through which infected B cells avoid effector CD8 T cell responses has not been characterized. In this study, we show that Salmonella infects and survives within all B1 and B2 cell subpopulations. B cells are infected with a Salmonella typhimurium strain expressing an ovalbumin (OVA) peptide (SIINFEKL) to evaluate whether B cells process and present Salmonella antigens in the context of MHC-I molecules. Our data showed that OVA peptides are presented by MHC class I K(b)-restricted molecules and the presented antigen is generated through proteasomal degradation and vacuolar processing. In addition, Salmonella-infected B cells express co-stimulatory molecules such as CD40, CD80, and CD86 as well as inhibitory molecules such as PD-L1. Thus, the cross-presentation of Salmonella antigens and the expression of activation molecules suggest that infected B cells are able to prime and activate specific CD8(+) T cells. However, the Salmonella infection-stimulated expression of PD-L1 suggests that the PD-1/PD-L1 pathway may be involved in turning off the cytotoxic effector response during Salmonella persistent infection, thereby allowing B cells to become a reservoir for the bacteria.
Departamento de Biomedicina Molecular Centro de Investigación y Estudios Avanzados del IPN, México City CP 07360, Mexico.
Marcela
M
Lopez-Medina
Department of Microbiology and Molecular Genetics, University of California, Irvine School of Medicine, Irvine, CA, USA.
Araceli
A
Perez-Lopez
Instituto Nacional de Salud Pública, Secretaría de Salud y Asistencia, Cuernavaca, Morelos CP 62100, Mexico.
Celia
C
Alpuche-Aranda
Departamento de Biomedicina Molecular Centro de Investigación y Estudios Avanzados del IPN, México City CP 07360, Mexico. Electronic address: vortiz@cinvestav.mx.
Vianney
V
Ortiz-Navarrete
D000818:Animals; D017951:Antigen Presentation / Q000276:immunology; D000942:Antigens, Bacterial / Q000276:immunology / Q000378:metabolism; D016175:B-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D060890:B7-H1 Antigen / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D045142:Cross-Priming / Q000276:immunology; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D012475:Salmonella / Q000276:immunology*; D012480:Salmonella Infections / Q000276:immunology* / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000276:immunology; D014617:Vacuoles / Q000276:immunology / Q000378:metabolism
D000942:Antigens, Bacterial; D060890:B7-H1 Antigen; D015395:Histocompatibility Antigens Class I
B cells; CD8 T cells; Cross-presentation; PD-L1; Salmonella