Difference between Antigen and Pathogen

Published on April 6, 2016

The functions of pathogens and antigens are connected, and in this article we will see what the connection and the difference between the two entities are.


antigen vs pathogen
A presentation of Dendritic Cells Antigen

Antigen refers to the molecule that is responsible for triggering a response in the human immune system upon the invasion of foreign microorganisms. Once the immune system notices the presence of malevolent foreign activity in the body, it starts producing antibodies, which work  on destroying undesired foreign molecules.

Staphylococcus epidermidis
A microscopic image of Staphylococcus epidermidis – one of roughly a thousand bacteria species which can be pathogenic and are usually present on the surface of the human skin.

In biology, pathogen describes anything that invades the human organism and causes various diseases.

There are several categories of pathogens:

  1. Bacterial pathogens. These refer to bacteria that can potentially cause diseases. Examples include mycobacterium tuberculosis, which brings the disease named after it, and streptococcus, which brings pneumonia.
  2. Viral pathogens. These are also known as viruses. One example of a widespread disease caused by a virus is influenza.
  3. Fungal pathogens. These mostly attack plants, but can also invade the human organism.
  4. Prionic pathogens. These have an abnormal structure without the nucleus that other pathogens have. One example of a disease they bring is encephalopathy (of which one variant is Mad Cow disease).

Antigen vs Pathogen

What is the difference between antigen and pathogen?

To put it simply, the antigen is a part of the pathogen that is noticeable by the human immune system, triggering the latter to become responsive.

Antigens come in all kinds of molecules. They can take the form of proteins, nuclear acids, or even fats. Paradoxically, antigens help pathogens to invade human cells, but at the same time, help the immune system to recognize the invading germ.

Comparison chart

Antigen Pathogen
Is a molecule inside a pathogenInvades the human organism
Often helps pathogen to infiltrate the human organismCauses people to become sick