Antiapoptotic serine protease inhibitors contribute to survival of allergenic T_H2 cells.

BACKGROUND:The mechanisms that regulate maintenance of persistent T_H2 cells and potentiate allergic inflammation are not well understood. OBJECTIVE:The function of serine protease inhibitor 2A (Spi2A) was studied in mouse T_H2 cells, and the serine protease inhibitor B3 (SERPINB3) and SERPINB4 genes were studied in T_H2 cells from patients with grass pollen allergy. METHODS:Spi2A-deficient T_H2 cells were studied in in vitro culture or in vivo after challenge of Spi2A knockout mice with ovalbumin in alum. Expression of SERPINB3 and SERPINB4 mRNA was measured in in vitro-cultured T_H2 cells and in ex vivo CD27^-CD4⁺ cells and innate lymphoid cell (ILC) 2 from patients with grass pollen allergy by using quantitative PCR. SERPINB3 and SERPINB4 mRNA levels were knocked down in cultured CD27^-CD4⁺ cells with small hairpin RNA. RESULTS:There were lower levels of in vitro-polarized T_H2 cells from Spi2A knockout mice (P < .005) and in vivo after ovalbumin challenge (P < .05), higher levels of apoptosis (Annexin V positivity, P < .005), and less lung allergic inflammation (number of lung eosinophils, P < .005). In vitro-polarized T_H2 cells from patients with grass pollen allergy expressed higher levels of both SERPINB3 and SERPINB4 mRNA (both P < .05) compared with unpolarized CD4 T cells. CD27^-CD4⁺ from patients with grass pollen allergy expressed higher levels of both SERPINB3 and SERPINB4 mRNA (both P < .0005) compared with CD27⁺CD4⁺ cells. ILC2 expressed higher levels of both SERPINB3 and SERPINB4 mRNA (both P < .0005) compared with ILC1. Knockdown of either SERPINB3 or SERPINB4 mRNA (both P < .005) levels resulted in decreased viability of CD27^-CD4⁺ compared with control transduced cells. CONCLUSION:The Serpins Spi2A in mice and SERPINB3 and SERPINB4 in allergic patients control the viability of T_H2 cells. This provides proof of principle for a therapeutic approach for allergic disease through ablation of allergic memory T_H2 cells through SERPINB3 and SERPINB4 mRNA downregulation.

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