The lymph node stromal laminin α5 shapes alloimmunity

Abstract

Lymph node stromal cells (LNSC) regulate immunity through constructing lymphocyte niches. LNSC produced Laminin α5 (Lama5) regulates CD4 T cells but the underlying mechanisms of its functions are poorly understood. Here we showed depleting Lama5 in LNSC resulted in decreased Lama5 protein in the LN cortical ridge (CR) and around high endothelial venules (HEV). Lama5 depletion affected LN structure with increased HEV, upregulated chemokines and cell adhesion molecules, and led to greater numbers of Treg in T cell zone. Mouse and human T cell transendothelial migration and T cell entry to LN were suppressed by Lama5 through the receptors a6 integrin and α-dystroglycan. During immune responses and allograft transplantation, depleting Lama5 promoted antigen specific CD4 T cell entry to the CR through HEV, suppressed T cell activation and altered T cell differentiation to suppressive regulatory phenotypes. Enhanced allograft acceptance resulted from depleting Lama5 or blockade of T cell Lama5 receptors. Lama5 and Lama4:Lama5 ratios in allografts were associated with the rejection severity. Overall, our results demonstrated that stromal Lama5 regulated immune responses through altering LN structures and T cell behaviors. The study delineated a stromal Lama5-T cell receptors axis that can be targeted for immune tolerance modulation.