The present invention relate to the discovery that BTLA, IL-7 and ROR?t modulate the activity and expression of ?d? cells. Specifically, the present invention provides methods of modulating ?d? cell homeostasis and function by regulating expression of BTLA. The present invention further provides agents which modulate the activity and expression of BTLA, RORyt and IL-7 and methods for screening of such agents. The present invention also provides methods for treating autoimmune or inflammatory diseases using modulators of BTLA, RORyt and IL-7.