The suffix -kin is used in naming interleukin-type substances except for interleukin 3 (IL-3), which was classified as a pleiotropic colony-stimulating factor and assigned the "plestim" stem (e.g., daniplestim).
The "kin" nomenclature series was divided into subgroups with an adjuvant stem representing the numerical class of the interleukin followed by the kin suffix.
The subgroups are:
-nakin interleukin 1 derivatives
-onakin interleukin 1 a derivatives
-benakin interleukin 1 b derivatives
-leukin interleukin 2 derivatives
-trakin interleukin 4 derivatives
-penkin interleukin 5 derivatives
-exakin interleukin 6 derivatives
-eptakin interleukin 7 derivatives
-octakin interleukin 8 derivatives
-nonakin interleukin 9 derivatives
-decakin interleukin 10 derivatives
-elvekin interleukin 11 derivatives
-dodekin interleukin 12 derivatives