Memory T cells play a central role in regulating inflammatory responses during asthma. However, tissue distribution of effector memory (T<sub>EM</sub>) and central memory (T<sub>CM</sub>) T-cell subtypes, their differentiation, and their contribution to the persistence of lung tissue inflammation during asthma are not well understood. Interestingly, an increase in survival and persistence of memory T cells was reported in asthmatic lungs, which may suggest a shift toward the more persistent T<sub>CM</sub> phenotype. In this report, we investigated the differential distribution of memory T-cell subtypes during allergic lung inflammation and the mechanism regulating that. Using an OVA-sensitized asthma mouse model, we observed a significant increase in the frequency of T<sub>CM</sub> cells in inflamed lungs compared to healthy controls. Interestingly, adoptive transfer techniques confirmed substantial infiltration of T<sub>CM</sub> cells to lung tissues during allergic airway inflammation. Expression levels of T<sub>CM</sub> homing receptors, CD34 and GlyCAM-1, were also significantly upregulated in the lung tissues of OVA-sensitized mice, which may facilitate the increased T<sub>CM</sub> infiltration into inflamed lungs. Moreover, a substantial increase in the relative expression of T<sub>CM</sub> profile-associated genes (EOMES, BCL-6, ID3, TCF-7, BCL-2, BIM, and BMI-1) was noted for T<sub>EM</sub> cells during lung inflammation, suggesting a shift for T<sub>EM</sub> into the T<sub>CM</sub> state. To our knowledge, this is the first study to report an increased infiltration of T<sub>CM</sub> cells into inflamed lung tissues and to suggest differentiation of T<sub>EM</sub> to T<sub>CM</sub> cells in these tissues. Therapeutic interference at T<sub>CM</sub> infiltration or differentiations could constitute an alternative treatment approach for lung inflammation.
Endogenous Attenuation of Allergic Lung Inflammation by Syndecan-1
