Gut-Brain & Microbiome Learning Center · Module 6 of 12
Immune Signaling & Inflammation
Introduces interactions among the immune system, the gut and the nervous system.
The gastrointestinal system contains extensive immune activity. That makes sense: the intestinal environment is continually exposed to food, microorganisms and substances arriving from outside the body.
The immune system must respond to potential threats while also interacting with microorganisms and substances that are normally present. Because of this close relationship, immune signaling is an important area of microbiome and gut-brain research.
The Gut and the Immune System
The mucosal surfaces of the gastrointestinal tract contain many immune cells. The legacy NVL research material discusses gut-associated lymphoid tissue, often abbreviated GALT. GALT is part of the immune system associated with the gastrointestinal tract.
Researchers study how this system interacts with:
- microorganisms
- intestinal cells
- microbial products
- antibodies
- cytokines
- other immune cells
Immunoglobulin A
The legacy material also discusses immunoglobulin A, or IgA. IgA is an antibody associated with mucosal surfaces, including the gastrointestinal tract. It participates in interactions between the immune system and substances encountered at these surfaces.
Researchers study IgA and other immune components to better understand how the body manages its relationship with intestinal microorganisms.
What Are Cytokines?
Immune cells communicate using signaling molecules. One important group of these molecules is known as cytokines. Cytokines participate in regulating immune responses.
The legacy research material discusses several cytokines in relation to gut-brain and autism research. Differences in particular inflammatory markers have been reported in some studies. However, identifying an altered immune marker does not establish what caused the alteration or whether it caused a developmental condition.
Inflammation Is a Process, Not a Single Diagnosis
The word "inflammation" is often used very broadly. Scientifically, inflammatory activity involves networks of immune cells, signaling molecules and biological responses. Different forms of inflammation can occur for different reasons.
An elevated immune marker in a study does not by itself demonstrate that a person has one specific inflammatory disorder. It also does not establish that reducing a particular marker would change autistic characteristics.
The Microbiome and Immune Signaling
Gut microorganisms live in close contact with the intestinal immune environment. Researchers therefore investigate how microbial communities and microbial products interact with immune pathways.
The legacy material explores relationships among:
- microbial composition
- intestinal barrier function
- cytokines
- immune cells
- microbial metabolites
These systems can influence one another, making it difficult to reduce the biology to a single pathway.
Microglia and the Brain
The legacy research material also discusses microglia. Microglia are immune-related cells found in the central nervous system. Researchers study microglial biology in many areas of neuroscience and neurodevelopment.
The old research material describes experimental work examining relationships among microbial status, immune signaling and microglial biology. Much of the mechanistic evidence discussed in this area comes from animal models.
Maternal Immune Activation Models
The legacy material also discusses maternal immune activation, or MIA, animal models. Researchers use these models to study how immune activity during pregnancy may affect biological development in offspring.
Some experiments described in the legacy material examined relationships among:
- immune signaling
- microbial composition
- intestinal permeability
- cytokines
- behavioral changes
These are experimental models. They should not be interpreted as a direct model of every autistic person or as proof that a particular microbial or immune pathway causes autism.
Immune Signaling and Autism Research
Researchers have reported immune-system differences in some groups of autistic participants. These findings have contributed to continued investigation of immune signaling and neurodevelopment.
But autism is heterogeneous. A finding observed in one research population may not be present in another. Immune differences may also reflect many biological and environmental factors.
For these reasons, researchers continue to investigate rather than assume a single immune explanation for autism.
What We Know
The gastrointestinal tract and immune system interact extensively. Gut microorganisms and microbial products encounter and interact with the intestinal immune environment.
Cytokines, antibodies and immune cells participate in communication within this system.
What Researchers Are Studying
Researchers continue to investigate relationships among:
- gut microbial communities
- intestinal barrier function
- immune signaling
- microbial metabolites
- nervous-system biology
- neurodevelopment
Animal models have provided important mechanistic clues, while human studies continue to examine whether particular immune findings are reproducible and clinically meaningful.
What Remains Uncertain
Immune-system differences have not established one universal immune cause of autism. It is also not established that changing a particular cytokine, microbial population or inflammatory marker will change core autistic characteristics.
Association should not be interpreted as causation.