The human brain has immune cells that separate us from primates, but it is also a weakness

A type of immune cell found only in humans that persists throughout an individual's development, remaining present even into adulthood.

What makes the human brain different from that of primates, no matter how close our place on the tree of life? In a study that looked at the type of cells found in the prefrontal cortex (PFC), scientists from Yale University found that only human properties make the difference.

The report, published in the journal Science on August 25, points out that this human trait also predisposes us to neurological diseases, such as paranoia, depression and autism.

A tomographic drawing of the human brain.

In the study, the researchers particularly focused on the posterior region of the dorsolateral prefrontal cortex (dlPFC), a part of the brain that exists only in primates and plays a crucial role in supporting higher level cognitive support. Using RNA sequencing, the researchers found large amounts of genes in hundreds of thousands of cell samples taken from the dlPFC region in humans, chimpanzees, macaques and marmosets.

'We consider the posterior region of the lateral prefrontal cortex as a core component of human identity, but until now it is not clear how they exist only in humans and separate us from primates. different,' said Professor Nenad Sestan of Yale University. 'Now, science has more clues'.

To better understand these differences, the team looked for cells that only exist in humans. After grouping together clusters of cells with similarities, they discovered 109 similar types of primate cells and five that are not found in all species. That includes microglia, which are a type of immune cell that exists only in the brain and only in humans. In addition, they found a type of cell found in both humans and chimpanzees.

An illustration of a primate. (Photo: stock.adobe.com).

A type of immune cell found only in humans that persists throughout an individual's development, and remains present even into adulthood. Scientists speculate that these cells play an important role in keeping the brain healthy, but not in the process of fighting disease.

'We humans live in a different environment, with a unique way of life when compared to other primates; glia cells, including microglia, are very sensitive to these differences." 'The type of immune cell microglia present in the human brain is probably representative of the human immune response to the environment'.

Further analyzing the gene map of microglia cells, the Yale team also unexpectedly discovered the existence of the FOXP2 gene. According to data obtained from related studies, variants of the FOXP2 gene are associated with diseases related to language and communication delays. Research has shown that FOXP2 is associated with neurological diseases such as autism, paranoia, and epilepsy.

Professor Sestan and his colleagues found that the FOXP2 gene confers traits that are unique to primates, and that play an important role in the development of human-only microglia cells.

"FOXP2 has intrigued researchers for decades, but we still don't know what sets humans apart from primates," said study co-author Ma Shaojie. 'We are delighted to have discovered FOXP2, as it opens new avenues in language and neurological disease research'.