EDNRB and melanoma: Since RB49 is generated by in vivo gene immunization in mice, this mutation was retained during clonal selection of B lymphocytes and maturation of RB49 affinity.23 The recognition properties of ETB by RB49 are unique in that we have shown that RB49 is able to recognize the full range of ETB conformations presented on the surface of several melanoma cell lines.11