The investigators specifically focused on CD4+ T cell mediated immunity because of previous reports linking HLA class II-restricted autoimmunity to AA—e.g., putative autoreactive CD4+ T cell clones were obtained by culturing AA patients’ T cells with autologous hematopoietic progenitors (103, 104), and multiple studies reported an association of HLA DR15 with AA (105, 106). The gene discussed is CD4; the disease is Autoimmunity.