Monoclonal antibodies developed against Botryllus blood cell antigens bind to cells of distinct lineages during embryonic development

Monoclonal antibodies that bind to adult Botryllus blood cell surface antigens were used to detect and localize identical or cross‐reacting antigenic determinants on Botryllus embryonic cells. These anti‐Botryllus monoclonal reagents could be divided into three categories: 1) those that bound to most embryonic cell types, including all very early embryonic cells; 2) those that bound only to embryonic blood cells and a few other embryonic cell types; and 3) those that did not bind detectably to any embryonic cells.