Well that's disappointing…
While the science discussed by the Telegraph in this article is real, it omits seriously important context and misrepresents decades-old research as a breaking development in a way that could provide false hope to those suffering from depression. The interplay between the immune system and the mind is increasingly well established, but that doesn’t mean that science has established anything close to a new treatment for depression as a result of this understanding.
http://www.snopes.com/2017/09/19/can-depression-treated-anti-inflammatory-drugs/
A news story highlights the interplay between the immune system and depression, but it provides this information without crucial context.