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IL-15 Expression on RA Synovial Fibroblasts Promotes B Cell Survival

2012; Public Library of Science; Volume: 7; Issue: 7 Linguagem: Inglês

10.1371/journal.pone.0040620

1932-6203

Marta Benito, Yolanda García-Carmona, Alejandro Balsa, María-Belén Bautista-Caro, Irene Arroyo-Villa, Tatiana Cobo‐Ibáñez, María Gema Bonilla-Hernán, Carlos Pérez de Ayala, Paloma Sánchez‐Mateos, E. Martín‐Mola, María‐Eugenia Miranda‐Carús,

Chronic Lymphocytic Leukemia Research

Introduction The purpose of this study was to examine the role of RA Synovial Fibroblast (RASFib) IL-15 expression on B cell survival. Methods Magnetically sorted peripheral blood memory B cells from 15 healthy subjects were cocultured with RASFib. Results RASFib constitutively expressed membrane IL-15. Survival of isolated B cells cultured for 6 days, below 5%, was extended in coculture with RASFib to 52+/−8% (p<0.001). IL-15 neutralizing agents but not isotype controls, reduced this rate to 31+/−6% (p<0.05). Interestingly, rhIL-15 had no effect on isolated B cells but significantly increased their survival in coculture with RASFib. In parallel, B cell IL-15R chains were upregulated in cocultures. BAFF and VCAM-1, that are expressed on RASFib, were tested as potential candidates involved in upregulating B cell IL-15R. Culture of B cells in the presence of rhBAFF or rhVCAM-1 resulted in significantly increased survival, together with upregulation of all three IL-15R chains; in parallel, rhIL-15 potentiated the anti-apoptotic effect of BAFF and VCAM-1. Both BAFF and VCAM-1 neutralizing agents downmodulated the effect of RASFib on B cell survival and IL-15R expression. In parallel, rhIL-15 had a lower effect on the survival of B cells cocultured with RASFib in the presence of BAFF or VCAM-1 neutralizing agents. Peripheral blood B cells from 15 early RA patients demonstrated an upregulated IL-15R and increased survival in cocultures. Conclusion IL-15 expression on RASFib significantly contributes to the anti-apoptotic effect of RASFib on B cells. IL-15 action is facilitated by BAFF and VCAM-1 expressed on RASFib, through an upregulation of IL-15R chains.