How the Immune System Senses Danger: Immunology Researcher David Ojcius Explains

It’s no secret that we rely on our immune systems to fight off common infections. But what you might not know is that the immune system is highly evolved and can even sense danger, explains David Ojcius, the Assistant Dean of Research at University of the Pacific in San Francisco, California. 

The first thing to know is that there are categories — an innate immune system and an adaptive immune system that serve different roles. The innate immune system was once underestimated, but researchers now know this immune system has been evolving in organisms more than 750 million years ago. 

Innate Immune System Activates First 

At the first signs of an infection or an injury, the innate immune system is the one that kicks into action first to try and stave off rapid bacteria growth. It is less of specific response — the innate system that can sense patterns that could warrant an immune response. 

One of the most important elements when it comes to “sensing danger” by the innate immune system is the presence of these pattern recognition receptors, also known as PRRs — proteins which can identify molecules in pathogens as well as molecules that are released due to damaged cells. These patterns are more specifically known as damage-associated molecular patterns (DAMPs) that are caused by injury, and pathogen-associated molecular patterns (PAMPs) that respond to infections. 

The adaptive immune system is secondary and is more specific at targeting the pathogen that it has “learned” from previous encounters, notes David Ojcius. But while the innate immune system is not as effective in identifying individual threats (antigen-specific), it can detect what doesn’t belong there. Furthermore, many microorganisms recognized by innate response are due to repeating patterns in terms of structure, which differ from host cells — which is important in preventing healthy cell destruction when fighting off a threat. 

The Role of Inflammasomes

While the innate immune system is an important first line of defense against infection, its response to trauma or infections can trigger the formation of inflammasomes, explains David Ojcius. 

The inflammasomes from innate immune responses can be a double-edged sword. On one hand, they can be protective against infections, but they also trigger inflammatory responses that can be detrimental to health. 


When the DAMPs are released from trauma, they can form these inflammasomes that contribute to cell damage and post-trauma inflammatory disorders. While more research is needed to fully understand inflammasomes, there have been some targeted therapies developed to limit the damage from inflammation. There’s also a possible connection being examined between inflammasomes and Alzheimer’s disease.

The Immune System Detects Danger Before You Do 

When your immune system is working properly, you will not even notice how effective it is because it will detect and destroy threats before they have a chance to make you ill, explains David Ojcius. While the innate immune system can recognize and respond quickly to non-specific threats, the adaptive system is constantly learning. These two evolving systems work together in tandem to help keep you safe from rapidly evolving pathogens.

Research on immunology and the detection systems of the immune system continue to be fascinating topics of research.

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