a molecule or portion of a molecule capable of binding to the combining site of an antibody. For every given antigenic determinant, the body can construct a variety of antibody-combining sites some of which fit almost perfectly, and others which barely fit at all., the small site of an "antigen" to which the "antibody" can attach itself by its combining site. Several antigenic determinants may be carried by a single antigenic molecule., (struktuuriliselt tuntud) antigeense toimega molekuliosa