The Omenn's syndrome: Histological, immunohistochemical and ultrastructural evidence for a partial T cell deficiency evolving in an abnormal proliferation of T lymphocytes and S-100+/T-6+ Langerhans-like cells

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Abstract
A 7 month old female infant was affected by a rapidly fatal familial disease highly reminiscent of Omenn's syndrome. She presented with widespread eczematous lesions, hepatosplenomegaly, superficial lymphadenopathy, peripheral blood lymphocytosis, eosinophilia and hyper-IgE. An axillary lymph node was involved by a marked proliferation of T-3+/T-10 - lymphocytes admixed with S-100+/T-6+/Leu-3a+/Ia+ reticular cells which lacked typical LC granules; cell suspension study revealed that 90%–96% of the lymph node cells were T-11+/ T-3+ lymphocytes characterized by low expression of Leu-3a and T-8 antigens and by high expression of Ia antigens (52%). Peripheral blood T lymphocytes exhibited a similar distribution of surface phenotypes. The patient died of interstitial pneumonia and an autopsy was performed. The thymus was markedly atrophic and completely devoid of lymphocytes. The peri-arteriolar lymphoid sheets of the spleen were poorly developed and were mainly composed of T-8+ lymphocytes. The mediastinal nodes were rudimentary and were populated by T-3+/ T-10+ lymphocytes with low expression of Leu-3a and T-8 antigens. Our results raise the possibility that Omenn's syndrome is a peculiar primary immunodeficiency in which, despite early thymic involution, some abnormal T lymphocytes still develop in the peripheral lymphoid organs. Antigenic triggering of these cells might result in prominent proliferations of T lymphocytes and Langerhans-like cells which lead to the clinical manifestation of the disease.