[1] Heterologous (meaning 'derived from a different organism') refers to the fact that often the transferred protein was initially cloned from or derived from a different cell type or a different species from the recipient.
Methods for transferring foreign genetic material into a recipient cell include transfection and transduction.
The choice of recipient cell type is often based on an experimental need to examine the protein's function in detail, and the most prevalent recipients, known as heterologous expression systems, are chosen usually because they are easy to transfer DNA into or because they allow for a simpler assessment of the protein's function.
A heterologous source of therapeutic cells will have a much greater availability than either autologous or allogenic cellular therapies.
In contrast, two protomers form an isologous association when they contribute the same set of residues to the protomer-protomer interface.