Basic StudiesTreatment With Polyclonal Immunoglobulin During T-cell Reconstitution Promotes Naive T-cell ProliferationPires, Ana Elisabete* †; Afonso, Ana Filipa* †; Queirós, Ana* †; Cabral, Maria Salomé‡; Porrata, Luis§; Markovic, Svetomir N.§; Kaveri, Srini V.∥; da Silva, Maria Gomes†; João, Cristina* †Author Information *Instituto Gulbenkian Ciência, Immune Reconstitution–External Group, Rua da Quinta Grande, Oeiras †Centro de Investigação e Patobiologia Molecular (CIPM), Instituto Português de Oncologia de Lisboa, Francisco Gentil, EPE, R. Prof. Lima Basto ‡Faculdade de Ciências, Universidade de Lisboa. Centro de Estatística e Aplicações. Departamento de Estatística e Investigação Operacional, Lisboa, Portugal §Mayo Clinic, Internal Medicine Department, Division of Hematology, Rochester, MN ∥Centre de Recherche des Cordeliers, Equipe 16, Immunopathology and Therapeutic Immunointervention, Université Pierre et Maria Curie Paris 6, Paris, France All authors have declared there are no financial conflicts of interest in regards to this work. Funded by Fundação para a Ciência e a Tecnologia (PTDC/SAU-MII/65029/2006) and Associação Portuguesa contra a Leucemia (APCL 2006-30.4M.AP/MJ). Reprints: Ana Elisabete Pires, Centro de Investigação e Patobiologia Molecular (CIPM), Instituto Português de Oncologia de Lisboa, Francisco Gentil, EPE, R. Prof. Lima Basto, 1099-023 Lisboa, Portugal (e-mail: email@example.com). Received for publication October 6, 2009; accepted December 21, 2009 Journal of Immunotherapy: July-August 2010 - Volume 33 - Issue 6 - p 618-625 doi: 10.1097/CJI.0b013e3181d3cb19 Buy Metrics Abstract Natural antibodies are unique self molecules endowed with both suppressive and activating functions on various cells of the immune system and are recognized as a fundamental link between the adaptive and innate immune system. Here, we examine the role of natural antibodies, using polyclonal immunoglobulins (Ig), as a promoter of T-cell reconstitution in a context of lymphopenia. We have established a mouse model to mimic immunologic recovery in adult patients with severe hypothymic function subjected to autologous hematopoietic precursor cell transplantation. Thymectomized mice were transplanted and treated with low doses of Ig or its Fab or Fc fragments. The animals displayed, during early phases of Ig treatment, a significant increase of T-cell reconstitution displaying a naive CD4+phenotype. In addition, the Ig-treated animals exhibited an increase dilution of single-joint T-cell receptor excision circles (sjTRECs) in peripheral blood, suggesting an early increase in proliferation of T cells stimulated by the natural antibodies. These results unveil a novel and considerable effect of intravenous Ig treatment in situations of severe lymphopenia as a stimulator of proliferation of peripheral naive T cells, possibly protecting diverse immune repertoires. © 2010 Lippincott Williams & Wilkins, Inc.