He will be lining up against a club for whom he made his professional debut last year, but stressed: "There are no mixed emotions about this game at all.
"I was brought up in Edinburgh and I'm Edinburgh through and through.
"But it just so happened that Glasgow needed a centre and asked for me to go through which was good because at the time I needed the experience."
It was in January 2006 that Cairns, now 22, made his one appearance for Glasgow against Ospreys, after joining on loan from Edinburgh.
"It was slightly weird playing for Glasgow instead of Edinburgh," he recalled.
"But all the boys were brilliant and Sean [Lineen, the Glasgow coach] took me in training and gave me a game.
"I ended up getting on fairly early when I came on after 20 minutes.
"It was a good experience and I learnt a lot from my short time at Glasgow.
"Nevertheless I'm now playing for my hometown team and will be doing everything I can to beat them."
As well as precious Magners League points, Friday's game also offers each team the chance to stake a claim for the 1872 Challenge Cup, which will be awarded to the aggregate winner of the two matches between Scotland's remaining pro sides this season.
The Challenge Cup has not been contested since the 1998-99 season, and Edinburgh are the current holders.
With home advantage on their side on Friday, Edinburgh are eager not only for victory but a decent winning margin ahead of the mid-April return match in Glasgow.
They currently trail Glasgow by just one point in the Magners League and will start 2008 as Scotland's top team if they get the better of the Firhill side.
As well as Callam and Kerr, their fellow Scotland international Hugo Southwell has also recovered from injury to take his place in the squad.
While Callam and Kerr come into the starting XV after missing the Heineken Cup clash with Leinster due to neck and toe problems respectively, full-back Southwell starts on the bench after three games out with an ankle injury.