Stability of interleukin-1β, -4, -6, -8, -10, -13, interferon-γ and tumor necrosis factor-α in human sera after repetitive freeze-thaw cycles and long storage

•Cytokines (CKs) level should be measured immediately after the serum sample collection.•Serum samples storage for 24 h resulted in a decrease of 7 out of 8 tested CKs level.•Up to 2 freeze-thaw cycles mainly did not affect serum CKs level.•Six following freeze-thaw cycles affected the stability of all tested CKs.•Storage at −80 °C between freeze-thaw cycles is superior to -20 °C.