Mice created with full human immune systems for the first time

Researchers at The University of Texas Health Science Center at San Antonio have succeeded where many before them have failed, in engineering a type of mouse that has an immune response identical to humans.

While mice are commonplace in research and considered one of the best animals to work with, they're far from a perfect human substitute. A major challenge is the many genes in mice that diverge from human equivalents, so their immune system responds very differently to ours.

This new mouse type – known as TruHuX (aka truly human) or THX – stands to make this research barrier a thing of the past. With its fully functional human immune system, the mouse ultimately responds to treatment as any of us would.

Casali's team also started with immunodeficient mice (NSG W41 mutants), injecting human stem cells purified from umbilical cord blood through the animal's left ventricle. After a period of weeks to allow this graft to settle, the mice were hormonally conditioned with 17b-estradiol (E2) – estrogen. Previous research by the team had found that this potent estrogen form could boost stem-cell survival and lymphocyte differentiation, as well as activate antibodies in response to viruses and bacteria.

Ultimately, THX is a 'super-humanized' mouse, with a complete human immune system – lymph nodes, germinal centers, thymus human epithelial cells, human T and B lymphocytes, memory B lymphocytes and plasma cells – and one that could mount a response identical to ours.

Image source: Aaron Logan, Wikimedia Commons, CC BY-SA 4.0.