When antibodies 'cross-link' antigens, what are they exactly doing?

antibodies have two binding sites for antigens ( called the Fab regions of the antibody..if the antigen site that the antibody "recognizes"y recognize is present on two anigen molecules in close proximity then the antibody will bind to the site on each and link them together by the antibody acting as a bridge...if the antigen has many sites of recognition this linking can be quite extensive