This is the abbreviation for Komalay Jiyanaway Kurd (Committee for the Revival of the Kurds), the name by which the Iranian party Komala established in 1942 is often known. (Some scholars argue that the letter K actually stands for Kurdistan, instead of Kurds.) The J.K. eventually was instrumental in the foundation of the famous but ill-fated Mahabad Republic of Kurdistan in 1946.
Historical Dictionary of the Kurds. Michael M. Gunter.