Enables cytokine activity and interleukin-2 receptor binding activity. Involved in leukocyte activation involved in immune response; positive regulation of interleukin-17 production; and positive regulation of tyrosine phosphorylation of STAT protein. Acts upstream of or within negative regulation of B cell apoptotic process; positive regulation of B cell proliferation; and positive regulation of activated T cell proliferation. Predicted to be located in extracellular space. Implicated in several diseases, including Takayasu's arteritis; auditory system disease (multiple); autoimmune disease (multiple); carcinoma (multiple); and neurodegenerative disease (multiple). Biomarker of several diseases, including Zellweger syndrome; aggressive periodontitis; anogenital venereal wart; autoimmune disease (multiple); and uveitis (multiple).