CD169+ macrophages in lymph node and spleen critically depend on dual RANK and LTbetaR signaling

CD169+ macrophages reside in lymph node (LN) and spleen and play an important role in the immune defense against pathogens. As resident macrophages, they are responsive to environmental cues to shape their tissue-specific identity. We have previously shown that LN CD169+ macrophages require RANKL for formation of their niche and their differentiation. Here, we demonstrate that they are also dependent on direct lymphotoxin beta (LTβ) receptor (R) signaling. In the absence or the reduced expression of either RANK or LTβR, their differentiation is perturbed, generating myeloid cells expressing SIGN-R1 in LNs. Conditions of combined haploinsufficiencies of RANK and LTβR revealed that both receptors contribute equally to LN CD169+ macrophage differentiation. In the spleen, the Cd169-directed ablation of either receptor results in a selective loss of marginal metallophilic macrophages (MMMs). Using a RANKL reporter mouse, we identify splenic marginal zone stromal cells as a source of RANKL and demonstrate that it participates in MMM differentiation. The loss of MMMs had no effect on the splenic B cell compartments but compromised viral capture and the expansion of virus-specific CD8+ T cells. Taken together, the data provide evidence that CD169+ macrophage differentiation in LN and spleen requires dual signals from LTβR and RANK with implications for the immune response.

Marginal Zone B-cell Lymphoma of the Gasserian Ganglion: Case Report and Review of the Literature

Primary central nervous system lymphoma (PCNSL) is a rare subtype of extranodal non-Hodgkin's lymphoma that accounts for 4% of newly diagnosed central nervous system (CNS) tumors. Most primary lymphomas of the central nervous system are of the subtype of diffuse large B-cell lymphomas, which have highly aggressive behavior and may involve the brain, leptomeninges, eyes or spinal cord without evidence of systemic disease. Primary CNS lymphomas are very rare in immunocompetent patients, but their rates are increasing. So far, only 11 primary Gasser ganglion lymphomas have been reported, with an incidence of 2.5 cases per 30,000,000 inhabitants. However, B cell lymphomas of the marginal zone of the Gasserian ganglion have been very rarely reported. We report here a clinical presentation characteristic of B cell lymphoma of the marginal zone of the Gasser ganglion in an immunocompetent patient who was treated with surgery and radiotherapy, evolving with improvement of symptoms and without recurrence in 3 months of follow-up.