Primary structure and cross-reactivity

[Esch]

A common assumption about cross-reactivity is that it correlates with
sequence homology.  When working with peptides, one commonly encounters
cross-reactivity among peptides with little or no sequence homology.  This
is not unexpected since short peptides frequently are "loose" and can
assume varying shapes for antibody binding.  Does anyone have specific
examples of unexpected cross-reactivities that are not explained solely on
the basis of primary sequence information?

Thanks,  Bob Esch