Type 2 inflammation is a pattern of

immune response An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could ...

. Its physiological function is to defend the body against

helminths Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as schi ...

, but a dysregulation of the type 2 inflammatory response has been implicated in the

pathophysiology Pathophysiology ( physiopathology) – a convergence of pathology with physiology – is the study of the disordered physiological processes that cause, result from, or are otherwise associated with a disease or injury. Pathology is the ...

of several diseases.

Molecular biology

IL-25,

IL-33 Interleukin 33 (IL-33) is a protein that in humans is encoded by the ''IL33'' gene. Interleukin 33 is a member of the IL-1 family that potently drives production of T helper-2 (Th2)-associated cytokines (e.g., IL-4). IL33 is a ligand for ST2 ...

, and

TSLP Thymic stromal lymphopoietin (TSLP) is a protein belonging to the cytokine family. It is known to play an important role in the maturation of T cell populations through activation of antigen-presenting cells. TSLP is produced mainly by non-Haema ...

are alarmins released from damaged epithelial cells. These

cytokines Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...

mediate the activation of type 2

T helper cells The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are considere ...

(T_h2 cells), type 2 innate lymphoid cells (ILC2 cells), and

dendritic cells Dendritic cells (DCs) are antigen-presenting cells (also known as ''accessory cells'') of the mammalian immune system. Their main function is to process antigen material and present it on the cell surface to the T cells of the immune system. The ...

. T_h2 cells and ILC2 cells secrete IL-4, IL-5 and IL-13. IL-4 further drives CD4+ T cell differentiation towards the T_h2 subtype and induces

isotype switching Immunoglobulin class switching, also known as isotype switching, isotypic commutation or class-switch recombination (CSR), is a biological mechanism that changes a B cell's production of immunoglobulin from one type to another, such as from the ...

to IgE in B cells. IL-4 and IL-13 stimulate trafficking of eosinophils to the site of inflammation, while IL-5 promotes both eosinophil trafficking and production.

Dysregulation in human disease

Type 2 inflammation has been implicated in several

chronic diseases A chronic condition is a health condition or disease that is persistent or otherwise long-lasting in its effects or a disease that comes with time. The term ''chronic'' is often applied when the course of the disease lasts for more than three mo ...

: *

Asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...

Atopic dermatitis Atopic dermatitis (AD), also known as atopic eczema, is a long-term type of inflammation of the skin (dermatitis). It results in puritis, itchy, red, swollen, and cracked skin. Clear fluid may come from the affected areas, which often thickens o ...

* Chronic sinusitis with nasal polyps *

Eosinophilic esophagitis Eosinophilic esophagitis (EoE) is an allergic inflammatory condition of the esophagus that involves eosinophils, a type of white blood cell. In healthy individuals, the esophagus is typically devoid of eosinophils. In EoE, eosinophils migrate t ...

Persons with one type 2 inflammatory disease are more likely to have other type 2 inflammatory diseases.

Pharmacological targets

Several medicines have been developed that target mediators of type 2 inflammation: * IL-4-specific blockers: ** Altrakincept ** Pascolizumab * IL-5-specific blockers: **

Benralizumab Benralizumab, sold under the brand name Fasenra, is a monoclonal antibody medication which is developed by MedImmune for the treatment of asthma. It is directed against the alpha-chain of the interleukin-5 receptor ( CD125). Two phase III clinica ...

Mepolizumab Mepolizumab, sold under the brand name Nucala, is a humanized monoclonal antibody used for the treatment of severe eosinophilic asthma, eosinophilic granulomatosis, and hypereosinophilic syndrome (HES). It recognizes and blocks interleukin-5 (IL ...

Reslizumab Reslizumab is a humanized monoclonal antibody against human interleukin-5 (IL-5). Reslizumab binds specifically to IL-5, a key cytokine responsible for the differentiation, maturation, recruitment and activation of human eosinophils. By binding ...

* IL-13-specific blockers: **

Lebrikizumab Lebrikizumab ( INN) is a humanized monoclonal antibody and an experimental immunosuppressive drug for the treatment of asthma that cannot be adequately controlled with inhalable glucocorticoids. The drug was created by Tanox under the name ''TNX ...

Tralokinumab Tralokinumab sold under the brand names Adtralza (EU/UK) and Adbry (US) among others, is a human monoclonal antibody used for the treatment of atopic dermatitis. Tralokinumab targets the cytokine interleukin 13. The most common side effects in ...

* Dual IL-4 and IL-13 blockers: **

Dupilumab Dupilumab, sold under the brand name Dupixent, is a monoclonal antibody blocking interleukin 4 and interleukin 13, used for allergic diseases such as eczema (atopic dermatitis), asthma and nasal polyps which result in chronic sinusitis. It is ...

* IgE-blockers: ** Ligelizumab **

Omalizumab Omalizumab, sold under the brand name Xolair, is a medication used to treat asthma, nasal polyps, and urticaria (hives). Omalizumab is a recombinant DNA-derived humanized IgG1k monoclonal antibody that specifically binds to free human immunoglo ...

References

{{reflist Immunology Asthma Atopic dermatitis