Abstract: The present disclosure provides methods of treating inflammatory or autoimmune diseases (e.g., lupus nephritis) using CD6-ALCAM pathway inhibitors such as EQ001 and to methods and diagnostic tests for identifying subjects likely to respond to such inhibitors. In particular, the present disclosure provides diagnostic and therapeutic uses related to elevated levels of soluble ALCAM and/or CD6 protein and protein fragments in urine and other biological samples that are indicative of sensitivity to inhibitors of the CD6-ALCAM pathway (e.g., EQ001).