Thymic stromal lymphopoietin (TSLP) is a key factor in the development of allergic asthma. Numbers of T_H2 memory cells gradually increase in allergic patients with the progression of disease and persist in the lungs during remission, although the mechanism is not clear.

We sought to define the role of TSLP in T_H2 memory cell generation and maintenance in vivo.

Adoptive transfer of wild-type and thymic stromal lymphopoietin receptor (TSLPR)–deficient ovalbumin-specific CD4⁺ T cells before T_H2 sensitization was used to define T cell–specific TSLP effects. Atopic dermatitis and increased serum TSLP concentrations were induced by topical application of the vitamin D3 analog MC903. Memory cells in peripheral blood were monitored weekly with flow cytometry. Memory recall was tested after intranasal ovalbumin challenge.

TSLP signaling in CD4⁺ T cells is required for the generation/maintenance of memory cells after in vivo priming. TSLPR-deficient CD4⁺ T cells have no defects in proliferation but do not survive 1 week after sensitization, and increased TSLP expression during sensitization significantly increased the frequency of memory cells. Although in vitro–differentiated TSLPR-deficient T_H2 cells develop into memory cells with equal efficiency to wild-type cells, the recall response to airway antigen challenge is impaired. Moreover, after antigen challenge of mice with established T_H2 memory, TSLP signaling in CD4⁺ T cells significantly affects memory cell generation/maintenance from secondary effector cells.

TSLP signaling in CD4⁺ T cells is required for not only T_H2 memory cell formation in vivo but also the recall response of the memory cells to local antigen challenge.