Development of a transient CD4+CD8+ T cell subset in the cervical lymph nodes following intratracheal instillation with an adenovirus vector

Past studies have described the serendipitous appearance of peripheral CD4+CD8+ double-positive (DP) T cells in both humans and nonhuman primates usually following a viral infection or resulting from a malignancy. However, understanding the role of DP T cells has been hampered by the lack of their reproducible generation. Herein, we describe DP T cells produced after a single intratracheal or intranasal dose of recombinant adenovirus 2 or 5 vector into mice. In a time-dependent fashion, DP T cells localized only in the deep cervical lymph nodes but not in the lungs or in any of the respiratory lymph nodes. These DP T cells were TCRαβ+ and CD8αβ+, but not TCRγδ+ nor CD8αα+, suggesting that these cells are unrelated to intestinally derived DP T cells. Upon co-stimulation with anti-CD3 and anti-CD28, DP T cells showed increased expression of VLA-1, VLA-2, and CD69, and were more effective than CD4+ T cells in T helper cell activity, as evidenced by increased IgA, IgG, and IgM production. Such co-stimulation also favored the production of IFN-γ and IL-10 where CD4+ T cells were more inclined to produce IFN-γ and IL-2.