I have yet to find concrete proof, not theoretical hypothesis, that peptide aggregates lead to a de facto adverse immunological response.
The only proven immunological response is in the case of recombinant HGH that has indeed led to such an outcome. But rHGH is biological in origin as it is harvested from e.coli. The vast majority, if not ALL other peptides we use are synthetically produced in labs.
@Ghoul if you have any studies to the contrary, for commonly used peptides such as bpc157, tb500 etc, I would greatly appreciate some links