The present invention provides a chimeric antigen-receptor (CAR)-forming polypeptide comprising: (i) an antigen-binding domain; (ii) a coiled-coil spacer domain; (iii) a transmembrane domain; and (iv) an endodomain. The invention also provides a multimeric CAR formed by association of a plurality of CAR- forming polypeptides by virtue of association of their coiled-coil spacer domains.