A method of treating a malignant disease involving T cell exhaustion in a subject, with the proviso that said malignant disease is not a B cell malignancy, is disclosed. The method comprising administering to the subject a therapeutically effective amount of an agent capable of decreasing an activity or expression of CD84, thereby treating the malignant disease involving the T cell exhaustion. Also disclosed is a method of treating an autoimmune or inflammatory disease in a subject, the method comprising administering to a subject a therapeutically effective amount of an agent capable of decreasing an activity or expression of CD84. A method comprising administering to the subject a therapeutically effective amount of an agent capable of decreasing an activity or expression of SLAMF1, with the proviso that said agent is not an agent capable of decreasing an activity or expression of CD84, is also disclosed.