Linker for activation of T cells contributes to airway inflammation in an asthmatic mouse model

Allergic asthma is associated with airway inflammation and hyperresponsiveness caused by dysregulated production of cytokines secreted by allergen-specific helper T-type 2 (Th2) cells. The linker for activation of T cells (LAT) is a membrane-associated adaptor protein, which has been shown to take part in regulating T cell receptor (TCR) signaling and T cell homeostasis. In this study, we established an asthmatic mouse model to examine the changes in LAT levels during allergic airway disease and the effects of LAT transgenic expression on airway inflammation.

T cells from mouse lung tissues were isolated from allergen challenged (ovalbumin (OVA)) and control mice, and the purity of these isolated T cells was examined by fluorescence-activated cell sorter (FACS). Semi-quantitative RT-PCR and Western blotting were used to detect the expression of the LAT gene and LAT protein, respectively. After an intranasally administered mixture of pCMV-HA-LAT plasmid and Lipofectamine 2000, 24 hours before and 72 hours after allergen challenge, the BALF cell count and the differential cytologies were studied. In addition, IL-4 and IFN-γ levels in the BALF were determined by ELISA, and pathological changes in lung tissues were observed.

LAT protein and mRNA expression were decreased in lung T cells in a mouse model of allergen-induced airway disease. After intranasal administration of pCMV-HA-LAT, histopathological examination of the lungs showed that intervention with LAT overexpression prevented mice from developing airway inflammation, and the number of total cells, eosinophils, neutrophils, and lymphocytes in the BALF was reduced significantly compared with the OVA sensitized and challenged group. In addition, the Th2 cytokine IL-4 decreased, while the Th1 cytokine IFN-γ increased compared to the OVA sensitized and challenged group or the OVA sensitized group plus pCMV-HA treatment.

This study demonstrates that LAT might effectively diminish Th2 cytokine responses, lung histopathological changes and lung inflammation to allergen challenge in a model of experimentally induced asthma.