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Innate Immunity and UTI Susceptibility - Role of Genetics

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Urinary tract infection is a common condition, and the immune system plays an important role in dealing with it. Read the article to learn more about it.

Published At September 12, 2022
Reviewed AtFebruary 20, 2023


The urinary system consists of organs that work to eliminate waste products from the body. The kidneys filter blood, form urine, and maintain the body's fluid levels. The urine then travels to the urinary bladder through tubes known as ureters. Finally, the urine exits the body through the urethra. The urinary system is exposed to thousands of bacteria from the gut, but the immune cells protect against the bacteria under normal conditions. Bladder Infections occur when the immune cells fail to function, and the bacteria enter the urinary bladder through the urethra.

What Is a Urinary Tract Infection?

As the name suggests, a urinary tract infection is a urinary tract disease. It is a term used to describe an infection in any urinary tract organ. A bladder infection can affect children at any age and needs to be treated at the earliest. Several healthy bacteria are present in the skin and the bowel, but they are not allowed to enter the urinary system. In the case of bladder infection in patients, these bacteria enter the urinary tract through the skin or stools. As a result, the patient experiences fever, pain, and a burning sensation while passing urine.

What Are the Signs and Symptoms of Urinary Tract Infection?

Urinary tract infection is commonly seen in females because they have a shorter urethra than males. The signs and symptoms of urinary cystitis are listed below:

  • Fever.

  • Abdominal pain.

  • Weakness.

  • Nausea, vomiting, and diarrhea are commonly seen.

  • The urine flow is restricted so the patient can pass a few drops of urine each time.

  • Pain and burning sensation while urinating are commonly seen.

  • Urinary incontinence or urine leakage might be seen in some patients.

  • The urine appears cloudy and smells bad.

What Is Innate Immunity?

Immunity or immune response simply means the body’s response to inflammation or infection. The body contains certain antibodies activated when bacteria, viruses, or other foreign agents try to invade. The immune system recognizes and protects the body from harmful substances. These substances are known as antigens and are present on the surfaces of cells, fungi, viruses, and bacteria. Antigens do not need to be present only on the surface of living objects, non-living objects like toxins, drugs, chemicals, and foreign particles can also be antigens. The immune system releases antibodies that destroy or remove these antigens. Innate immunity refers to the defense system that the individual is born with. In other words, it is the body's natural immunity against a variety of diseases. Skin, gastric acid, mucus, and cough reflexes are some examples of innate immunity.

What Role Does Genetics Play in UTI Susceptibility and Innate Immunity?

A person's susceptibility to urinary tract infection varies according to the bacteria and the immune response. The following has been known so far in relation to the genetics of UTI susceptibility and innate immunity:

  1. Genetics plays an important role in common conditions like urinary tract infections, where genetic variations control the expression of genes in bacterial diseases.

  2. The urinary tract is continuously exposed to various microorganisms that reside in the digestive system. However, the urinary tract resists these infections because of the innate immune response.

  3. The kidneys, ureters, urinary bladder, and urethra are the principal organs of the urinary tract, and all of these organs are sterile except the urethra. The urine produced by the kidneys also secretes several factors that prevent bacterial colonization.

  4. The urinary tract is also lined by various immune cells that protect it from infection. These cells act as barriers and prevent the entry of pathogens into the urinary tract.

  5. Several genes and molecular mechanisms control the susceptibility of urinary tract infections.

  6. The immune system consists of a variety of signaling pathways and factors that control the expression of genes in urinary tract infections. When the immune system becomes damaged, the genes fail to function normally. As a result, the risk of infection increases. The genes present in the urinary tract recognize the exact bacterial strain and work to release the chemicals that help to kill them.

How Does the Innate Immune Response Protect the Urinary Tract?

The most important function of the urinary tract is to store urine for a prolonged period. Still, the urine contains many different toxins and bacteria, so it must remain under a tight barrier. So, the immune system must act so that the inflammatory response is generated only when the bacteria invade the urinary system. However, suppose the inflammatory response is terminated before the bacteria exit the urinary system. In that case, there is a possibility that the residual bacteria will persist in the urinary system and give rise to infections. The different innate immune cells present in the urinary tract that protect it from infections are listed below:

  • Epithelial Cells - The epithelial cells are present on the inner lining of the urinary tract and act as the first line of defense against bacteria. These cells secrete proteins and anti-inflammatory agents that inhibit bacterial growth and eliminate the virulence factors that encourage the growth of pathogenic microorganisms. Sometimes, these bacteria succeed in attaching to the epithelial cell layers. In such situations, the innate immune system commands the urinary bladder to shed the epithelial cells as a part of a protective response.

  • Neutrophils - They are the first immune cells that come into action during urinary tract infections. Studies have reported that neutrophil levels start elevating two hours after the infection and reach a peak within six hours. When the bacterial load decreases, the neutrophil levels also decrease. The neutrophils cross several cell layers to reach the invading microorganisms.

  • Macrophages - The entire population of macrophages resides in the urinary tract. When the bacteria enter the urinary tract, these macrophages get activated and release chemicals that prevent the inflammatory response. The chemicals released by the macrophages command the neutrophils to work against infection.

  • Mast Cells - Mast cells are present beneath the epithelium and close to the blood vessels of the urinary tract. They are also present in large numbers near the urinary bladder muscles. The exact mechanism of mast cell activation is still unknown. However, scientists believe that stressed epithelial cells might be responsible for mast cell activation.

How Are Urinary Tract Infections Managed?

  1. Antibiotics - Antibiotics are the first-line therapy in the management of urinary tract infections. The mode of administration of the drug depends upon the age of the patient. For example, in children two months or older, antibiotics are administered by mouth as liquids (syrups). The infection usually subsides in two to three days, but the entire course of antibiotics needs to be completed. Therefore, the doctor might recommend the diagnostic tests again to check if the antibiotics have worked against the infection or not. The commonly used antibiotics in urinary tract infections are listed below:

    • Cefixime.

    • Cephalexin.

    • Amoxicillin and Clavulanic acid.

    • Trimethoprim.

  2. Keep Hydrated: Drink plenty of water every day to avoid urinary cystitis. Water helps to dilute the urine, increases the speed of urine flow, and flushes out the bacteria from the body. On average, an adult must drink six to eight glasses of water daily.

  3. Healthy Bladder Habits - The patient must have healthy bladder habits, like urinating when the need arises, wiping from front to back after urinating, and not holding the urine for too long; when the urine remains in the body for a prolonged period, the risk of urinary tract infections increases.


Urinary tract infections are commonly seen in females because of the difference in the anatomy of their urinary tract. Infants and young children also experience urinary tract infections, but the condition goes unnoticed because they cannot express their symptoms. Genetics and innate immunity play a vital role in urinary tract infections. The human body comprises genes that control the immune response. If the genes are defective, the immune response fails to function. As a result, people tend to experience more urinary tract diseases. In addition, several immune cells are present in the urinary tract to protect it against bacteria. So, it is important to keep the urinary tract healthy by maintaining proper genital hygiene to keep the body free of diseases. Consult a urologist to learn more about urinary tract infections.

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Dr. Samer Sameer Juma Ali Altawil
Dr. Samer Sameer Juma Ali Altawil



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