Aldesleukin (Recombinant Human Interleukin-2): A Comprehensive Monograph on a Pioneering Immunotherapy

Section 1: Introduction to Interleukin-2 and the Development of Aldesleukin

1.1. The Physiological Role of Interleukin-2 (IL-2)

Interleukin-2 (IL-2) is a pleiotropic cytokine that functions as a central signaling molecule within the immune system, orchestrating the complex interplay between immune activation and tolerance.[1] Naturally produced by activated CD4+ and CD8+ T lymphocytes, IL-2 was originally identified as T-cell growth factor due to its critical role in promoting the proliferation, survival, and differentiation of various lymphocyte populations.[3] Its physiological functions are multifaceted. On one hand, IL-2 is a potent pro-inflammatory mediator, driving the expansion and enhancing the cytotoxic capabilities of effector T-cells and Natural Killer (NK) cells, which are essential for clearing pathogens and eliminating malignant cells.[2] On the other hand, it is indispensable for the maintenance of peripheral immune tolerance. IL-2 is fundamentally required for the development, survival, and function of regulatory T-cells (Tregs), a specialized subset of T-cells that suppress excessive immune responses and prevent autoimmunity.[1] This inherent duality—simultaneously promoting aggressive immune attacks and enforcing immune restraint—is determined by the concentration of IL-2 and the specific cellular context. This biological paradox is the cornerstone that explains its divergent therapeutic applications, from high-dose cancer immunotherapy to low-dose treatment for autoimmune disorders.

1.2. Development and Formulation of Aldesleukin (Proleukin®)