We report the development of thermoresponsive 4-mercaptoethylpyridine (MEP)-based chromatographic microsphere based resins for antibody separation that show switchable release abilities by adsorbing immunoglobulins at 40 degrees C and releasing the proteins at 5 degrees C. The thermoswitchable release properties were introduced to the porous resins by the grafting of linear poly(N-isopropylacrylamide) (PNIPAM) chains synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, which were modified to possess MEP end functionalities. Adsorption of gamma-globulins as a model antibody on the shortest PNIPAM-MEP (3 kDa) grafted microparticles display binding capacities of up to 20 g L-1 at 40 5 degrees C and a significant decrease in binding capacity to less than 2.5 g L-1 at 5 degrees C. By switching the temperature to 5 degrees C, the release of bound gamma-globulins is shown to be as high as 90%. The effects of polymer chain length on the binding capacity are studied in detail and found to be critical as they influence the density of MEP functionalities on the particle surfaces.