The main mechanism of this phenomenon in vivo is due to the prolongation of the cytokine half-life in circulation. Depending on the clone of IL-2 mAb, IL-2 ic  can selectively stimulate either CD25high (IL-2/JES6-1 complexes), or CD122high cells (IL-2/S4B6). IL-2/S4B6 immune complexes have high stimulatory activity for NK cells and memory CD8+ T cells and they could thus replace the conventional IL-2 in cancer immunotherapy. On the other hand, IL-2/JES6-1 highly selectively stimulate regulatory T cells and they could be potentially useful for transplantations and in treatment of autoimmune diseases. History
According to an immunology textbook: "IL-2 is particularly important historically, as it is the first type I cytokine that was cloned, the first type I cytokine for which a receptor component was cloned, and was the first short-chain type I cytokine whose receptor structure was solved. Many general principles have been derived from studies of this cytokine including its being the first cytokine demonstrated to act in a growth factor–like fashion through specific high-affinity receptors, analogous to the growth factors being studied by endocrinologists and biochemists". : 712 In the mid-1960s, studies reported "activities" in leukocyte-conditioned media that promoted lymphocyte proliferation. : 16  In the mid-1970s, it was discovered that T-cells could be selectively proliferated when normal human bone marrow cells were cultured in conditioned medium obtained from phytohemagglutinin-stimulated normal human lymphocytes. : 712  The key factor was isolated from cultured mouse cells in 1979 and from cultured human cells in 1980. The gene for human IL-2 was cloned in 1982 after an intense competition.
The active methylene group in that product is then nitrosated with sodium nitrite; the initial product spontaneously tautomerizes to afford the oxime (4). The bromoketone array in that intermediate constitutes a classical starting function for construction of thiazoles. Reaction of 4 with thiourea thus leads to formation of an aminothiazole moiety. Thus there is obtained the antibiotic cefdinir (5). References
External links
"Cefdinir". Drug Information Portal. U.S. National Library of Medicine.