Type 2 Inflammation

The human immune system has evolved to defend and protect us from infections caused by microbes and some types of cancers.  The cells responsible for these defenses originate in the bone marrow and circulate in the blood stream and lymphatic system.

The human immune system has evolved to defend and protect us from infections caused by microbes and some types of cancers. The cells responsible for these defenses originate in the bone marrow and circulate in the blood stream and lymphatic system.

Classically, host immunity is divided into innate and adaptive immune responses. The former reacts rapidly and non-specifically to pathogens, whereas the latter responds in a slower but specific manner, with the generation of long-lived immunological memory.

Innate immunity is mediated by immune cell populations such as myeloid cells, natural killer (NK) cells, innate lymphoid cells, and complement. Adaptive immunity is a relatively new evolutionary trait based on the immunoglobulin family (i.e., antibodies) and cells such as B- and T-lymphocytes.

During an infection, the innate immunity is the first to be triggered (i.e., the inflammatory reaction), taking no longer than minutes to hours to be fully activated. This is crucial for the host defense in the first phase of a new infection. While innate immunity is generally able to eliminate the pathogens efficiently, initial clearance of an infection can fail due to the high number or virulence of the invading pathogens. In these situations, lymphocytes and adaptive immune mechanisms are activated, which allows for specific recognition and elimination of the pathogen. The establishment of the adaptive immunity requires approximately 1–2 weeks and is important for host defense during the latter phases of an infection as well as secondary infections due to its capacity to “remember” and respond more effectively to restimulation.

Adaptive immunity is further subdivided into 2 types: humoral and cellular. Humoral immunity is mediated by antibodies which are also known as immunoglobulins. These antibodies are secreted by B-cells or B-lymphocytes. They are called B-lymphocytes because they are made in the bone marrow. Cellular immunity is mediated by in the thymus and thus named T-cells or T-lymphocytes.

T-lymphocytes have 2 main sub-populations called T-helper 1 cells (Th-1) and T-helper 2 cells (Th-2 cells). The main role of Th-1 cells is to defend against intracellular pathogens whereas Th-2 cells are mainly involved in defenses against large extracellular organisms such as parasites. These 2 cells fight infections and infestations by secreting different types of effector molecules called cytokines.

As we are now living in a more hygienic environment than our ancestors, we are encountering fewer water-borne pathogens such as parasites. As a result, the Th-2 cells, due to mysterious reasons, instead of fighting the parasites and pathogens, are now reacting against harmless substances such as pollen, dust mites, mold spores, food proteins, etc., mistaking them as potentially harmful.

Over the years, this evolutionary happening has now resulted in allergic diseases being mediated by “Type 2 inflammation.” This phenomenon is responsible for the “atopic march” which begins in infancy as eczema (i.e., atopic dermatitis) and evolving to affect various organs in later life.

Atopic dermatitis manifests in the skin and is characterized by itching, dryness, and inflammation of the skin. It is usually genetically determined by mutations in genes such as “filagrin.” The chronic inflammation of the skin leads to defects in the barrier functions of the skin, allowing easier access for foreign proteins into the body.

The other manifestations of Type 2 inflammation depend on the organ systems involved. Allergic rhinitis impacts the nasal passages and leads to
symptoms such as sneezing, nasal congestion, runny nose, post-nasal drip, watery eyes, red eyes, and/or itchy eyes. Asthma primarily impacts the lungs and causes airway inflammation, hyperreactivity, and wheezing.

Chronic rhinosinusitis with nasal polyps affects the upper airways leading to nasal obstruction, loss of smell, and persistent sinus infections. Eosinophilic esophagitis (EoE) impacts the gastrointestinal tract and can lead to difficulty swallowing, food impaction, and inflammation of the esophagus, whereas food allergies are a more systemic manifestation that may involve multiple organ systems and lead to reactions ranging from mild hives to life-threatening anaphylaxis.

All of the above conditions have the common thread of Type 2 inflammation. They present differently, though, depending on which tissues are primarily affected, it is important to recognize early signs. It is important for allergists to know the connections because we can then diagnose them earlier. This allows the allergy specialists to better anticipate the course of various allergic and immunologic diseases and possibly even interrupt the atopic march leading to a decrease in allergic symptoms in the patient.

The board certified allergists at Black & Kletz Allergy have 3 office locations in the Washington, Northern Virginia, and Maryland metropolitan area. The allergy doctors at Black & Kletz Allergy treat both adult and pediatric patients. We have offices in Washington, DC, McLean, VA (Tysons Corner, VA), and Manassas, VA. All 3 of our offices have on-site parking and both the Washington, DC and McLean, VA offices are Metro accessible. In addition, the McLean, VA office has a complementary shuttle that runs between our office and the Spring Hill metro station on the silver line. For an appointment, please call our office or alternatively, you can click Request an Appointment and we will respond within 24 hours by the next business day. The allergy specialists at Black & Kletz Allergy have been helping patients with hay fever, food allergies, asthma, eczema, hives, sinus disease, insect sting allergies, immunological disorders, and medication allergies for over 50 years. We understand the underlying type 2 inflammation that comes along with allergies and asthma and we aim to decrease or eliminate it. If you suffer from any allergy or immune problem, it is our mission to improve your quality of life by reducing or preventing your unwanted and annoying allergy symptoms.