RPS4Y1 and X-linked disease: Taking advantage from the high uniformity and unlimited quantity of monoclonal antibodies and from the targeting of a gender (male) specific biomarker expressed in any type of male fetal cell, the new antibody here described against the male RPS4Y1 protein would enable the development of strategies for the isolation of circulating male fetal cells with the necessary sensitivity for the development of routine non-invasive prenatal diagnosis of X-linked diseases.