Eosinophils

Overview

Eosinophils are a type of white blood cell (WBC) and belong to the granulocyte group, also known as polymorphonuclear cells. They are an integral part of the immune system, playing a crucial role in allergy management, inflammation, and defense against parasitic and fungal infections.

Eosinophils circulate in the bloodstream under normal conditions in relatively fixed numbers, maintained by a balance between production, circulation, and programmed cell death (apoptosis). These cells are identified by their bilobed nucleus and prominent eosinophilic granules, which stain vividly with eosin. Any abnormality in their morphology, such as three or more lobes, may suggest a pathological process or abnormal cell development.

Eosinophils are also significant because they express IgE receptors and cytokine receptors, making them highly responsive in allergic and immune-related reactions.

Symptoms

Alterations in eosinophil counts—whether increased (eosinophilia) or decreased (eosinopenia)—are often linked to underlying health conditions. The symptoms generally relate to the disease process that causes these variations:

1. High eosinophil count (Eosinophilia):
   1. Allergic rhinitis (sneezing, runny nose, itching)
   2. Asthma symptoms like wheezing and breathlessness
   3. Reactions to severe drug exposure
   4. Skin issues like psoriasis or systemic lupus erythematosus
   5. Chronic inflammatory joint pain from rheumatoid arthritis
   6. Signs of parasitic infection (abdominal pain, diarrhea, fatigue)
2. Low eosinophil count (Eosinopenia):
   1. Fatigue and weakness due to underlying infection or steroid use
   2. Symptoms of Cushing’s syndrome (weight gain, high blood pressure, mood changes)
   3. Reactions to drugs, ACTH, or thyroxine
   4. Increased susceptibility to bacterial infections

Thus, the symptoms are usually indirect markers of conditions affecting eosinophil levels rather than signs caused directly by the cells themselves.

Causes

The causes of abnormal eosinophil levels are divided into two categories: eosinophilia (increase) and eosinopenia (decrease).

1. Causes of Increased Eosinophils (Eosinophilia):
   1. Allergic conditions such as rhinitis and asthma
   2. Long-term dialysis in kidney-related conditions
   3. Immunodeficiency disorders
   4. Parasitic infestations like hookworm, tapeworm, trichinella, and schistosoma
   5. Pulmonary eosinophilia syndromes
   6. Drug-induced reactions
   7. Chronic inflammatory diseases like rheumatoid arthritis and psoriasis
   8. Autoimmune diseases such as systemic lupus erythematosus (SLE)
   9. Hyper eosinophilic syndrome (rare but severe condition)
2. Causes of Reduced Eosinophils (Eosinopenia):
   1. Hormonal changes in Cushing’s syndrome
   2. Excessive use of drugs like steroids, epinephrine, or ACTH
   3. Overproduction of thyroxine (hyperthyroidism)
   4. Acute bacterial infections

Understanding these causes allows physicians to use eosinophil count as a diagnostic indicator for a wide range of conditions.

Risk Factors

Certain groups of people are more prone to abnormal eosinophil levels due to lifestyle, environmental, or medical reasons. Risk factors include:

1. Chronic allergies or asthma patients frequently exhibit higher eosinophil counts.
2. Individuals in parasitic-endemic regions, where exposure to worms and other parasites is common.
3. Patients on long-term medication, especially those using steroids, ACTH, or thyroxine, which can suppress eosinophil production.
4. Autoimmune disease sufferers, such as those with lupus or rheumatoid arthritis, often show increased eosinophil counts.
5. Individuals with endocrine disorders, such as Cushing’s syndrome or hyperthyroidism.

These risk factors emphasize the importance of routine blood testing to monitor eosinophil levels, especially in high-risk individuals.

Prevention

Prevention of abnormal eosinophil levels is largely tied to managing the underlying conditions that affect their production or destruction. Key preventive measures include:

1. Managing Allergies and Asthma
   1. Early treatment of allergic rhinitis and asthma can control eosinophil overproduction.
   2. Use of prescribed inhalers and allergy medications helps maintain balance.
2. Parasitic Infection Control
   1. Maintaining hygiene, safe food practices, and deworming treatments in endemic areas reduce the risk of parasitic-induced eosinophilia.
3. Safe Drug Use
   1. Avoiding unnecessary medications and following medical prescriptions minimizes drug-induced eosinophilia or eosinopenia.
4. Monitoring Chronic Diseases
   1. Regular health check-ups for autoimmune, kidney, and endocrine disorders ensure early detection of abnormal eosinophil levels.
5. Lifestyle and Immunity Support
   1. Balanced diet, stress management, and adequate rest help maintain immune homeostasis, indirectly regulating eosinophil levels.