What is the Difference Between H. Pylori IGG and IGA

The main difference between H. pylori IgG and IgA is that IgG provides the majority of antibody-based immunity against invading pathogens, while IgA prevents colonization of pathogens. Furthermore, H. pylori IgG is the predominant circulating form of antibodies, while IgA mainly occurs in the mucosal areas. Also, H. pylori IgG antibodies can be first detected after the declension of IgM antibody titer, while IgA antibodies occur after a few weeks of infection. Moreover, IgG helps to qualitatively diagnose H. pylori infection, while IgA helps to diagnose chronic-active gastritis.

In brief, IgG and IgA are two types of immunoglobulin isotopes raised against H. pylori infection. Here, H. pylori is a gram-negative, helically-shaped, microaerophilic bacterium that often occurs in the stomach.  

Key Areas Covered 

1. H. Pylori
     – Definition, Characteristics, Importance
2. What is H. Pylori IgG
     – Definition, Characteristics, Importance
3. What is H. Pylori IgA
     – Definition, Characteristics, Importance
4. What are the Similarities Between H. Pylori IgG and IgA
     – Outline of Common Features
5. What is the Difference Between H. Pylori IgG and IgA
     – Comparison of Key Differences

Key Terms

Campylobacter pylori, H. pylori, H. pylori IgA, H. pylori IgG, Mucosal Areas, Serum, Stomach Infection

H. Pylori – Definition, Characteristics, Importance 

Helicobacter pylori or Campylobacter pylori is a Gram-negative, helical-shaped bacterium that was first identified by Australian doctors Barry Marshall and Robin Warren in 1982. The bacterium penetrates the mucoid lining of the stomach through its helical shape, and thus, establishes the infection. Furthermore, H. pylori are associated with the mucosa-associated lymphoid tissue in the stomach, esophagus, colon, rectum, and around the eye as well as in the lymphoid tissue of the stomach. 

Figure 1: H. pylori Crossing the Mucus Layer of the Stomach

Moreover, H. pylori spread through the faecal-oral route. Accordingly, over 50% of the World’s population has H. pylori infection in their upper respiratory tract. Specifically, the developing countries have much higher infection levels. Therefore, it is one of the most common types of chronic bacterial infections. However, the majority of these infections remain asymptomatic.

Clinically, dyspepsia or indigestion occurs in the upper respiratory tract with symptoms such as discomfort, bloating, pain, nausea, and burping. Also, chronic gastritis, gastric ulcers, and gastric cancer are the complications of the disease. More often, the basic diagnostic methods of the infection include the urea breath test, faecal antigen assay, and tissue biopsy. Unfortunately, H. pylori infection does not heal spontaneously and also, the pathogen may persist life long. However, the majority of infected patients develop antibodies against H. pylori.

What is H. Pylori IgG 

H. pylori IgG is the type of antibodies, appearing with the declension of the titer of IgM antibodies. Importantly, it is the predominant form of antibodies in the serum in the H. pylori infection. Also, the main function of IgG antibodies in the H. pylori infection is preventing the invading pathogen.

Figure 2: H. Pylori Infection in a Gastric Foveolar Pit

However, the detection of IgG antibodies in the H. pylori infection only helps to diagnose the disease qualitatively. Therefore, positive results do not indicate the presence of gastrointestinal disease. Hence, assay results should be utilized along with other clinical and laboratory data to assist patient management decisions.  

What is H. Pylori IgA 

H. pylori IgA is the second type of antibodies tested for H. pylori infection. Significantly, it occurs after fewer weeks from the infection. However, IgA antibodies occur in the mucosal areas, preventing the colonization of pathogens.

Figure 3: Structure of IgG and IgA

Moreover, the detection of IgA antibodies is important in the diagnosis of the H. pylori infections in patients, having the duodenal disease and in the monitoring of the eradication of H pylori following antimicrobial therapy. Although the systemic response of the IgA type is less pronounced, the significant levels may indicate a more severe inflammation.  

Similarities Between H. Pylori IgG and IgA 

• H.pylori IgG and IgA are two types of immunoglobulin isotopes, forming in response to the H. pylori infection. 
• They are antibodies that are glycoprotein molecules produced by the plasma B cells. 
• Also, they specifically recognize and bind to the H. pylori antigens. 
• In addition to that, they play a critical role in the destruction of H. pylori by developing adaptive immune responses. 
• Therefore, the detection of antibodies helps to diagnose the disease as well as to monitor the treatments. 
• Similarly, both types of antibodies persist in the body for a long period. 
• They are two of the three types of testing antibodies upon H. pylori infection while the third type of antibodies is the IgM. 
• However, testing both antibodies does not allow the differentiation between acute and chronic infections. 

Difference Between H. Pylori IgG and IgA 

Definition 

H. pylori IgG refers to the predominant form of antibodies in the serum, being specific to the H. pylori infection.  Meanwhile, H. pylori IgA refers to the form of antibodies, occurring in the mucosal areas specific to H. pylori.

Structure 

H. pylori IgG is a monomer, while H. pylori IgA is a dimer.

Appearance 

H. pylori IgG antibodies can be first detected after the declension of IgM antibody titer, but pylori IgA antibodies occur after a few weeks of infection.

Location 

H. pylori IgG is the predominant circulating form of antibodies, but H. pylori IgA mainly occurs in the mucosal areas.

Function 

H. pylori IgG provides the majority of antibody-based immunity against invading pathogens, while H. pylori IgA prevents colonization by pathogens.  

Turnaround Time 

The turnaround time of H. pylori IgG is 1-3 days, while the turnaround time of H. pylori IgA is 1-4 days. 

Method of Detection 

H. pylori IgG is detected by chemiluminescence immunoassay (CLIA), but H. pylori Ig A is detected by enzyme-linked immunosorbent assay (ELISA).

Role in Disease Diagnosis 

H. pylori IgG helps to qualitatively diagnose the infection, while H. pylori IgA helps to diagnose chronic-active gastritis.

High Levels 

Higher levels of H. pylori IgG antibodies indicate the chronic infection, while high levels of H. pylori IgA in the systemic circulation indicate severe gastric inflammation. 

Conclusion

H. pylori IgG is the type of antibodies, forming after the declension of its IgM antibody titer. Also, it is the predominant form of serum antibodies. And, the main function of H. pylori IgG is to prevent the invading of pathogens. In diagnostics, it helps to diagnose the diseases; its higher levels indicate chronic infection. On the other hand, H. pylori IgA is another type of antibodies, occurring after a few weeks from the infection. Specifically, it occurs in the mucosal areas, preventing the colonization of the pathogen. Also, it helps to diagnose chronic active gastritis. Therefore, the main difference between H. pylori IgG and IgA is their role in the infection. 

References:

1. “Helicobacter Pylori Antibodies, IgG.” LabCorp, Laboratory Corporation of America® Holdings and Lexi-Comp Inc., 29 Jan. 2020, Available Here. 
2. “Helicobacter Pylori Antibodies, IgA.” LabCorp, Laboratory Corporation of America® Holdings and Lexi-Comp Inc., 29 Jan. 2020, Available Here.
3. “Anti-Helicobacter Pylori ELSIA (IgA).” EUROIMMUN, EUROIMMUN AG. Available Here.

Image Courtesy:

1. “Ulcer-causing Bacterium (H.Pylori) Crossing Mucus Layer of Stomach” By Zina Deretsky, National Science Foundation (Public Domain) via Commons Wikimedia   
2. “Immunohistochemical detection of Helicobacter (1) histopatholgy” By User: KGH – Own work (CC BY-SA 3.0) via Commons Wikimedia   
3. “Mono-und-Polymere” By Martin Brändli (brandlee86) – Own work (CC BY-SA 2.5) via Commons Wikimedia