Essential role of CD4 + T cells for the activation of group 2 innate lymphoid cells during respiratory syncytial virus infection in mice.

Aim: To investigate whether and how CD4(+ )T cells contribute to ILC2 activation during respiratory syncytial virus (RSV) infection. Methods: The methods of flow cytometry, quantitative PCR and ELISA were used in the present study. Results: Depletion of CD4(+) T cells diminished the numbers of lung ILC2s as well as their ability to produce type 2 cytokines. CD4(+ )T cell-mediated ILC2 activation is related to IL-2. The main cellular source of IL-2 was CD4(+ )T cells. Depletion of CD4(+) T cells decreased IL-2 levels in the lungs of RSV-infected mice. IL-2 can directly stimulate ILC2 proliferation and promote ILC2s to produce cytokines. Treatment of mice with neutralizing anti-IL-2 monoclonal antibodies diminished ILC2 activation. Conclusion: These results suggest that CD4(+) T cells contribute to RSV-induced ILC2 activation partly via producing IL-2.