The immune system is home to various cells, all of which have their own jobs to do when it comes to keeping the body functioning and healthy. Immune cells are broken up into several categorizations: lymphocytes, monocytes/macrophages, and neutrophils. Within the lymphocyte grouping, there are T-cells, B-cells, and natural killer cells.
T-cells are designed to start a reaction against specific pathogens, which then signals B-cells to start creating antibodies – proteins designed to help the body fight off pathogens. Natural killer cells are then tasked with activating receptors that lead to the production of small proteins that can kill the pathogen or limit its ability to spread throughout the body.
The immune system uses all of these cells to help keep you healthy. However, in some diseases or infections, levels of immune cells can change dramatically. One such cell is often negatively affected by disease: a natural killer cell known as CD57. But what is a CD57 cell marker? And how is it related to chronic illnesses such as Lyme disease?
What is CD57?
The CD in CD57 stands for “cluster differentiation”, which is a type of protocol used to identify molecules on the surface of certain cells. The number attached to the CD is assigned to help researchers and medical scientists identify which specialized proteins, known as monoclonal antibodies, are recognized by the CD molecules. Essentially, it helps researchers keep track of cells that interact with one another, as well as which patterns occur when it comes to cellular differentiation.
CD57 itself is a specialized molecule found on the surface of natural killer cells. As mentioned above, these natural killer cells are vital for fighting off pathogens, so being able to identify these cells using CD57 is important when investigating the body for disease or immune system irregularities. CD57 can also be found on T-cells. When the molecule is found, it signals that certain cells have limited functionality and are often senescent.

What is a CD57 cell marker?
A cell marker is a type of marker or identifier that is expressed in specific cells at a certain time. These markers are able to help researchers see the growth patterns or differentiation patterns of cells, which can lead them to being able to diagnose or treat diseases. The CD57 marker can act as a marker on both natural killer cells and T-cells.
These markers can mean different things. In some cases, a marker can indicate that the cell is not where it should be in terms of growth and replication, and that cell proliferation is low even though the cells themselves have high potential to be viable killers of pathogens. These markers can also be used to help identify diseases.
What does a CD57 test show?
A CD57 test is a form of blood test designed to examine cells that have the CD57 marker and their levels. It is often used to detect low or high levels that may indicate disease. In many cases, a CD57 test is used to help identify Lyme disease because the number of natural killer cells with this marker tend to be much lower than normal in Lyme patients. While medical researchers are unsure why, it has become a helpful test when checking someone for the bacterial infection.
While CD57 can be found on both natural killer cells and T-cells, the blood test that looks for the marker is focused on natural killer cells only. T-cells with the CD57 marker tend to go unexamined.
What should your CD57 be?
When it comes to levels of CD57 in the blood, the optimal amount will vary within the range outlined by medical professionals. In terms of a healthy individual, a CD57 natural killer cell count could be anywhere between 60 to 360 uL. This range is designed to take into account the differences in individuals while still maintaining a set number doctors can use as a baseline. If a person happens to fall out of that baseline (i.e. if their CD57 level is lower or higher), it indicates that there is something amiss going on.

What does a high CD57 count mean?
A high CD57 count indicates that the level of CD57 within the tested blood is higher than the top of the baseline (360). Typically, higher amounts of CD57 indicate that there are more natural killer cells in the body than what is needed. High levels, just like low levels, could be indicative of a disease.
What is a normal CD57 level in Lyme patients?
In Lyme disease patients, CD57 tends to be much lower than the baseline range (i.e. typically much lower than 60). While researchers are unsure why, it has given them an opportunity to use the CD57 marker as a way to diagnose Lyme disease or monitor its progression.
By examining CD57 markers, medical professionals can come to a diagnostic conclusion for people who could be suffering from various conditions such as Lyme disease.