Inflammation is recognized by having four cardinal symptoms (the four “-ors”): calor (heat), rubor (redness), tumor (swelling), and dolor (pain). In the 19th century, an additional symptom, loss of function, was also attributed to inflammation. Many diseases have some chronic inflammatory component, where the inflammatory stimuli is not an invading pathogen. Though there are a great number of these diseases, click on the conditions below to see how inflammation plays a role. Inflammation can also play a role in certain neurological diseases, which you can read about on our Neuroinflammation page.


Atherosclerosis

Atherosclerosis begins as a build-up of cholesterol, fatty acids, and calcium in the artery which attracts macrophages in an attempt to engulf the proteins that transfer fat (such as LDL, low density lipoprotein). These macrophages turn into foam cells which accumulate and release cytokines, reactive oxygen species, and growth factors which recruit additional immune cells, including T helper 1 cells that release pro-inflammatory cytokines, amplifying the immune response at the site of the lesion.

 

Type 2 Diabetes

In type 2 diabetes, insulin resistance develops due to pancreatic β-cells being unable to compensate for an excess of nutrients in the blood. Stressed pancreatic cells and adipocytes can produce pro-inflammatory cytokines such as IL-1β, TNFα, and CCL2, encouraging recruitment of macrophages and lymphocytes, causing tissue inflammation. This inflammation can cause cell death or cell damage that causes further insulin resistance.

 

Autoimmune Diseases

Autoimmune diseases occur through an abnormal immune response against tissues or proteins that naturally occur in one’s own body. Since the elimination of the antigen or offending tissue is not possible, these diseases must typically be treated through immunosuppression. There are over 80 diseases that are characterized by autoimmunity, but here are some that you’ve probably heard of before, along with the tissue that the immune response is mounted in: psoriasis (skin), type 1 diabetes (pancreas), Crohn’s disease (digestive tract), rheumatoid arthritis (joints), lupus (connective tissue), and multiple sclerosis (central nervous system).

 

Cancer

Inflammation can have opposing roles in cancer. During tumor initiation, type 1 inflammation can be a source of reactive oxygen species and cellular damage, causing genetic instability and may encourage the transformation of cells into a malignant phenotype. After a tumor has developed, type 2 inflammation may dominate, with cancer cells releasing immunosuppressive cytokines that down-regulate the cytotoxic response and encourage pro-resolving mediators. Cells may express immune checkpoint receptors that engage T cells to induce tolerance, allowing the tumor to escape immunosurveillance.

 

Allergy

In allergic disease, the immune system will mount a response against harmless substances, such as pollen or certain proteins in food. This hypersensitivity to allergens causes an IgE-mediated immune response which activates mast cells to release histamine, causing a localized immune response. Though allergies are commonly treated using anti-histamines, in severe cases, it can be treated using immunosuppressive drugs such as corticosteroids.

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Atherosclerosis begins as a build-up of cholesterol, fatty acids, and calcium in the artery which attracts macrophages in an attempt to engulf the proteins that transfer fat (such as LDL, low density lipoprotein). These macrophages turn into foam cells which accumulate and release cytokines, reactive oxygen species, and growth factors which recruit additional immune cells, including T helper 1 cells that release pro-inflammatory cytokines, amplifying the immune response at the site of the lesion.

In type 2 diabetes, insulin resistance develops due to pancreatic β-cells being unable to compensate for an excess of nutrients in the blood. Stressed pancreatic cells and adipocytes can produce pro-inflammatory cytokines such as IL-1β, TNFα, and CCL2, encouraging recruitment of macrophages and lymphocytes, causing tissue inflammation. This inflammation can cause cell death or cell damage that causes further insulin resistance.

Autoimmune diseases occur through an abnormal immune response against tissues or proteins that naturally occur in one’s own body. Since the elimination of the antigen or offending tissue is not possible, these diseases must typically be treated through immunosuppression. There are over 80 diseases that are characterized by autoimmunity, but here are some that you’ve probably heard of before, along with the tissue that the immune response is mounted in: psoriasis (skin), type 1 diabetes (pancreas), Crohn’s disease (digestive tract), rheumatoid arthritis (joints), lupus (connective tissue), and multiple sclerosis (central nervous system).

Inflammation can have opposing roles in cancer. During tumor initiation, type 1 inflammation can be a source of reactive oxygen species and cellular damage, causing genetic instability and may encourage the transformation of cells into a malignant phenotype. After a tumor has developed, type 2 inflammation may dominate, with cancer cells releasing immunosuppressive cytokines that down-regulate the cytotoxic response and encourage pro-resolving mediators. Cells may express immune checkpoint receptors that engage T cells to induce tolerance, allowing the tumor to escape immunosurveillance.

In allergic disease, the immune system will mount a response against harmless substances, such as pollen or certain proteins in food. This hypersensitivity to allergens causes an IgE-mediated immune response which activates mast cells to release histamine, causing a localized immune response. Though allergies are commonly treated using anti-histamines, in severe cases, it can be treated using immunosuppressive drugs such as corticosteroids.