The present invention is based, at least in part, on the finding that certain molecules are preferentially associated with
effector T cells or regulatory T cells. Accordingly, immune responses by one or the other subset of cells can be preferentially modulated. The invention pertains, e.g., to methods of modulating (e.g., up- or down-modulating), the balance between the activation of regulatory T cells and
effector T cells leading to modulation of immune responses and to compositions useful in modulating those responses. The invention also pertains to methods useful in diagnosing, treating, or preventing conditions that would benefit from modulating
effector T cell function relative to
regulatory T cell function or from modulating
regulatory T cell function relative to effector
T cell function in a subject. The subject methods and compositions are especially useful in the diagnosis, treatment or prevention of conditions characterized by a too-vigorous effector
T cell response to antigens associated with the condition, in the diagnosis, treatment or prevention of conditions characterized by a weak effector
T cell response, in the diagnosis, treatment or prevention of conditions characterized by a too-vigorous
regulatory T cell response, or in the diagnosis, treatment, or prevention of conditions characterized by a weak regulatory
T cell response.