The CRLF2 protein heterodimerizes with the IL7R alpha chain (CD127) to form the heterodimeric thymic stromal lymphopoietin receptor (TSLPR) that is aberrantly overexpressed at high levels on the surface of CRLF2-rearranged (CRLF2-R) B-ALL cells and is easily detectable by flow cytometric immunophenotyping [10]. The gene discussed is CRLF2; the disease is acute lymphoblastic leukemia.