PI3K p110d Is Expressed by gp38CD31 and gp38CD31 Spleen Stromal Cells and Regulates Their CCL19, CCL21, and LTbR mRNA Levels

The role of p110d PI3K in lymphoid cells has been studied extensively, showing its importance in immune cell differentiation, activation and development. Altered T cell localization in p110d-deficient mouse spleen suggested a role for p110d in non-hematopoietic stromal cells, which maintain hematopoietic cell segregation. We tested this hypothesis using p110d mouse bone marrow to reconstitute lethally irradiated p110d or p110d (which express catalytically inactive p110d) recipients, and studied localization, number and percentage of hematopoietic cell subsets in spleen and lymph nodes, in homeostatic conditions and after antigen stimulation. These analyses showed diffuse T cell areas in p110d and in reconstituted p110d mice in homeostatic conditions. In these mice, spleen CD4 and CD8 T cell numbers did not increase in response to antigen, suggesting that a p110d stroma defect impedes correct T cell response. FACS analysis of spleen stromal cell populations showed a decrease in the percentage of gp38CD31 cells in p110d mice. qRT-PCR studies detected p110d mRNA expression in p110d spleen gp38CD31 and gp38CD31 subsets, which was reduced in p110d spleen. Lack of p110d activity in these cell populations correlated with lower LTbR, CCL19 and CCL21 mRNA levels; these molecules participate in T cell localization to specific spleen areas. Our results could explain the lower T cell numbers and more diffuse T cell areas found in p110d mouse spleen, as well as the lower T cell expansion after antigen stimulation in p110d compared with p110d mice. Citation: Zotes TM, Spada R, Mulens V, Pérez-Yagüe S, Sorzano CO, et al. (2013) PI3K p110d Is Expressed by gp38CD31 and gp38CD31 Spleen Stromal Cells and Regulates Their CCL19, CCL21, and LTbR mRNA Levels. PLoS ONE 8(8): e72960. doi:10.1371/journal.pone.0072960 Editor: Jörg Hermann Fritz, McGill University, Canada Received December 28, 2012; Accepted July 17, 2013; Published August 29, 2013 Copyright: 2013 Zotes et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by the Spanish Ministry of Science and Innovation (SAF-2007-60498, SAF-2008-00471, SAF-2011-23639 to DFB, AP2007-01711 to TMZ), CSIC (Intramural Project 200820I084 to DFB), and the Research Network in Inflammation and Rheumatic Diseases (RIER) of the ISCIII-MSPS Cooperative Research Thematic Network program (RD08/0075/0015 to DFB). RS holds a FPI pre-doctoral fellowship (BES-2009-016547) from the Spanish Ministry of Economy and Competitiveness (MINECO). VM holds a predoctoral fellowship from Fundación La Caixa-CNB program. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: KO is a consultant for GlaxoSmithKline. This does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials. * E-mail: [email protected] . These authors contributed equally to this work.