Sorry, I should have mentioned that the Syrian Christian tradition claims to descend from St. Thomas in 52 AD. See
http://www.malankarachurch.org/malankara/MalankaraChurch2.htm
And the third century I wrote seems like the product of a confused or deluded mind: I must have misremembered 4th century as 3rd. I apologize for taking up board space with incorrect information.