"Heterologous" means something that is different or unrelated, especially when referring to genes, cells, or organisms that come from a different species.
Could undetectably low levels of UNC - 7S expression driven by heterologous promoters in AVB account for rescue? (neuraldevelopment.biomedcentral.com)
Although the reasons why Plasmodium proteins are difficult to express in heterologous expression systems are not clear, several protein characteristics, such as high molecular mass (> 60 kDa), presence of export motifs, and atypical signal peptide sequences negatively impact recombinant expression [12]. (malariajournal.biomedcentral.com)
Because barbiturate anesthetics (e.g., pentobarbital) are reported to block 5 - HT3 signaling in heterologous expression systems (Barann et al., 2000; Rüsch et al., 2007), we tested the effects of different anesthetics (pentobarbital vs urethane) on chorda tympani responses. (jneurosci.org)