Antigen cells have antigen fragments and histocompatibility complexes on their surface. T-cells learn to recognize specific antigens and can trigger responses when they appear in the body, so these cells circulate throughout the body and present the fragments to them. These cells are an important part of the immune system, and as antigen exposure increases, they become more complex. This can be intentional, such as through vaccination, or unintentional, such as through contact with sick people or handling contaminated objects.
These cells, also known as antigen presenting cells, can ingest antigens and process them into fragments that they display on their surface. B lymphocytes and phagocytic cells like macrophages are examples of antigen cell types. They float around the body, interacting with T-cells that can recognize antigen fragments and the HSC. They tend to congregate in the lymph nodes during an active infection.
T-cells cannot recognize most antigens on their own. They rely on antigen cells to process the antigens and repackage them in a way that the T cells can recognize. Similarly, an antigen cell cannot initiate an immune response by itself. If a patient’s T-cells are malfunctioning, the antigen cells may function normally but lack T-cells to latch onto, preventing the immune system from responding to an infection.
In some cases, an antigen cell can serve as a tumor marker. For example, the protein carcinoembyronic antigen has been linked to a variety of cancers. This protein levels spike in a developing fetus, but they should be very low in adults. If they are unusually high, the patient may be suffering from a cancerous growth, such as colon cancer. This protein can aid cancer spread by allowing cells with the antigen to bind more easily to body tissues.
A blood test may be used by a doctor to check for the presence of certain antigen cell types. This can be used to see if a patient has been exposed to an antigen and if his or her body has produced an immune response. A small sample of blood can be taken by the doctor and sent to a lab for screening to look for antigen cells and determine their concentration in the blood.