Immature T-Cell Populations in Lymph Nodes of Castleman Disease and Angioimmunoblastic T-Cell Lymphoma Suggest Alternate Sites of T-Cell Development,

Abstract

3238 A central dogma of human immunology is that proliferation of immature T-cells, and their development after release from the bone marrow, occurs in the central thymus. Recently, we identified several patients with aberrant polyclonal immature TdT+ precursor T-cell populations in extra-thymic lymphoid tissues. Here we demonstrate that immature precursor T-cell populations, with a cortical thymocyte phenotype, in fact, are expanded in extra-thymic lymphoid tissues of patients with Castleman disease (P < 0.001; n = 29), and angioimmunoblastic T-cell lymphoma (P = < 0.001; n =31) and increased in cases of Castleman disease in association with follicular dendritic cell sarcoma (Figures 1 and 2). Analysis of the proliferation marker, MiB-1, and the morphologic presence of mitoses reveal that these populations are undergoing extra-thymic proliferation and expansion, arguing against simple release from the central thymus and sequestration in these extra-thymic organs. Finally, these populations of immature T-cells are not associated with a particular anatomic site (i.e. neck or mediastinum). These findings challenge the dogma that proliferation of immature human T-cell populations occurs nearly exclusively in the central thymus and demonstrates that stimulation and significant proliferation of extra-thymic immature T-cells does, and can occur in a subset of patients. Disclosures: No relevant conflicts of interest to declare.

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