Myosin light chains 9 and 12 are functional ligands for CD69 that regulate airway inflammation

Recent decades have witnessed a rapid worldwide increase in chronic inflammatory disorders such as asthma. CD4(+) T helper 2 cells play critical roles in the pathogenesis of allergic airway inflammation, and CD69 expression on activated CD4 T cells is required to induce allergic inflammation in tissues. However, how CD69 mechanistically controls allergic inflammation remains poorly defined. In lymphoid tissues, CD69 regulates cellular retention through inhibition of S1P1 expression and requires no specific ligands to function. In contrast, we show herein that myosin light chain (Myl) 9 and Myl12 are new functional ligands for CD69. Blockade of CD69-My19/12 interaction ameliorates allergic airway inflammation in ovalbumin-induced and house dust mite-induced mouse models of asthma. Within the inflamed mouse airways, we found that the expression of My19/12 was increased and that platelet-derived My19/12 localized to the luminal surface of blood vessels and formed intravascular netlike structures. Analysis of nasal polyps of eosinophilic chronic rhinosinusitis patients revealed that My19/12 expression was increased in inflammatory lesions and was distributed within net-like structures in the intravascular space. In addition, we detected My19/12 in perivascular spaces where many CD69(+) cells were positioned within My19/12 structures. Thus, CD69-My19/12 interaction is a key event in the recruitment of activated CD69(+) T cells to inflamed tissues and could be a therapeutic target for intractable airway inflammatory diseases.