" When an animal is infected, either naturally or by experimental injection, with a bacterium, virus, or other foreign body, the animal recognises this as an invader and acts in such a way as to remove or destroy it. "
- Cesar Milstein

When an organism encounters a foreign body such as a bacterium or virus, it recognizes this intruder and initiates a defense mechanism aimed at neutralizing or eliminating it from its system. This process underscores how all living beings have evolved intricate immune systems to safeguard their health.

The quote delves into the fundamental principle that underpins our biological response to threats like infections or diseases. It highlights the innate ability of organisms, including humans and animals, to detect foreign entities as harmful invaders and launch a targeted defense. By doing so, it underscores the complexity and efficiency of immune responses in maintaining overall health and well-being. Furthermore, this statement also touches upon the broader concept of survival mechanisms that have evolved over millennia, illustrating how these systems play a crucial role not just in fighting off immediate threats but also in ensuring long-term resilience against various pathogens.

Cesar Milstein was an eminent British biochemist born in Argentina who made significant contributions to immunology. He is best known for his pioneering work on monoclonal antibodies, which are used extensively in medical research and diagnostics today. His insights into the immune system have had profound implications across multiple fields of science, including medicine and biotechnology.