Fas ligand expression on T cells is sufficient to prevent prolonged airway inflammation in a murine model of asthma

Abstract

Our previous studies revealed that, in a murine model of asthma, mice that received Fas-deficient T cells developed a prolonged phase of airway inflammation, mucus production, and airway hyperreactivity that failed to resolve even 6 weeks after the last challenge. To investigate how Fas-Fas ligand (FasL) interaction occurs between T cells and other cells in vivo, Gld mice with abnormalities of the FasL signaling pathway were used. The reconstituted mice were made by transferring T cells from B6 or Gld mice to Rag(-/-) or FasL-deficient Rag(-/-) mice. We found that Rag(-/-) mice that received B6 T cells resolved the airway inflammation, whereas FasL-deficient Rag(-/-) mice that received Gld T cells developed a prolonged airway inflammation at Day 28, with decreased IFN-gamma production. Both FasL-deficient Rag(-/-) mice that received B6 T cells and Rag(-/-) mice that received Gld T cells also had completely resolved their airway inflammation by Day 28 after challenge. Interestingly, FasL-deficient Rag(-/-) mice that received Gld T cells eventually resolved airway inflammation at Day 42, with a similar level of IFN-gamma production to that of control group. These results demonstrate that FasL expression on either T cells only or non-T cells only was sufficient for the eventual resolution of airway inflammation, and the prolonged airway inflammation in FasL-deficient Rag(-/-) mice that received Gld T cells was correlated with decreased IFN-gamma production by Gld T cells.

Figure 1.

Resolution of airway inflammation is delayed in Fas ligand (FasL)–deficient mice. Gld and B6 mice were sensitized with inactivated Schistosoma mansoni eggs, challenged with soluble egg antigen (SEA) (10 μg/mouse), killed on Days 4 (B6 n = 8, Gld n = 9) and 14 (B6 n = 5, Gld n = 4) after the last challenge, and cells harvested by bronchoalveolar lavage (BAL). The total cell numbers in the BAL of B6 and Gld mice were analyzed by trypan blue staining. The type of BAL cells (eosinophils and CD3 T cells) was determined by calculating the absolute number of each cell type from the FACS profiles and by the total numbers of BAL cells. *P < 0.05, ***P < 0.001. Error bars represent SEM.

Figure 2.

Increased lung inflammation and mucus production in Gld mice. (A) Representative sections of lungs at Day 14. Lung tissues from B6 and Gld mice were fixed in 4% paraformaldehyde and embedded in paraffin. Hematoxylin and eosin (H&E)–stained sections for analysis of airway inflammation and periodic acid Schiff (PAS)–stained sections for analysis of mucus-containing cells are presented. (B) Quantification of perivascular and peribronchial inflammation and mucus production. *P < 0.05, ***P < 0.001. Error bars represent SEM.

Figure 3.

FasL expression on either T cells only or non–T cells only was eventually sufficient to prevent chronic airway inflammation. B6 and Gld T cells were adoptively transferred into Rag^−/− and Gld.Rag^−/− mice 1 day before sensitization (noted as B6 > Rag^−/−, B6 > Gld.Rag^−/−, Gld > Rag^−/−, and Gld > Gld.Rag^−/− mice, respectively). The four groups of reconstituted mice were sensitized, challenged, and killed on Days 4 (A), 14 (B), and 28 (C) after the final challenge, and the BAL was analyzed. The total BAL cell numbers, cell types, and absolute numbers were calculated as described in Materials and Methods. (D) BAL eosinophil counts were determined for Days 4, 14, 28, and 42. These eosinophil numbers for Days 4, 14, and 28, shown in A, B, and C, are also included to provide a more complete picture of the entire time course that was tested. A total of 5–14 mice per group per time point were analyzed. *P < 0.05. Error bars represent SEM.

Figure 4.

Increased lung inflammation and mucus production in Gld > Gld.Rag^−/− mice at Day 28 (A). Representative sections from B6 > Rag^−/− (panels 1 and 2), B6 > Gld.Rag^−/− (panels 3 and 4), Gld > Rag^−/− (panels 5 and 6), and Gld > Gld.Rag^−/− (panels 7 and 8) mice killed at Day 28 after the last challenge are shown. The H&E-stained sections (panels 1, 3, 5, and 7) and PAS-stained sections (panels 2, 4, 6, and 8) are shown. (B) Quantification of perivascular and peribronchial inflammation and mucus production from these four groups of mice at Day 28. (C) Representative H&E-stained sections from B6 > Rag^−/– and Gld > Gld.Rag^−/– mice at Day 42 after the last challenge are shown. **P < 0.01, *** P < 0.001. Error bars represent SEM.

Figure 5.

Decreased IFN-γ production by Gld T cells in the Gld > Gld.Rag^−/− mice at Day 28. (A) BAL and spleen T cells from B6 > Rag^−/− mice and Gld > Gld.Rag^−/− mice at Day 28, and (B) lung and spleen T cells from B6 > Rag^−/− mice and Gld > Gld.Rag^−/− mice at Day 42, were restimulated with SEA, and measured by Bioplex system, as described in Materials and Methods for IFN-γ and IL-5 (data not shown). *P < 0.05. Error bars represent SEM.