The present invention relates to novel alternative splice transcripts (AST) for MICA (MHC class I related chain alpha) encoding novel MICA protein isoforms and uses thereof. In particular, the present invention relates to an isolated polypeptide at least 80% of identity with a sequence selected from the group consisting of SEQ ID NO:1 (MICA-A), SEQ ID NO:2 (MICA-B1), SEQ ID NO:3 (MICA-B2) SEQ ID NO:4 (MICA-C) and SEQ ID NO: (MICA-D).