HLA-G and chronic kidney disease: In various observational studies both in non-dialyzed [320] and dialyzed CKD patients [321,322,323,324] and even in populations not specifically selected because of CKD [325,326,327] β2-microglobulin has been associated to hard outcomes or to surrogate outcomes like parameters of inflammation [323], vascular stiffness [323,324] or bone remodeling [326,327].