The COVID-19 pandemic highlighted just how differently people can respond to the same infection. Some individuals experience mild symptoms, while others become severely ill. This striking contrast raises an important question. Why would two people infected by the same pathogen have such different outcomes?

Much of the answer lies in differences in genetics (the genes you inherit) and life experience (your environmental, infection, and vaccination history). These influences shape our cells through subtle molecular modifications known as epigenetic changes. These changes do not alter the DNA sequence itself. Instead, they control whether specific genes are turned “on” or “off,” helping determine how cells behave and function.

Researchers at the Salk Institute have introduced a comprehensive epigenetic catalog that separates the effects of inherited genetics from those of life experiences across multiple immune cell types. This new cell type-specific database, published in Nature Genetics on January 27, 2026, provides insight into why immune responses vary from person to person and could help guide the development of more precise, personalized treatments.