R76: Other abnormal immunological findings in serum

R76.9: Abnormal immunological finding in serum, unspecified

Such substances may be certain antibodies, for example.

The immune system protects the body from pathogens and foreign substances. The immune system can also destroy cells in the body that have pathologically changed. Some of the immune system’s antibodies can make pathogens and foreign substances visible to the immune system. Other antibodies attack pathogens or foreign substances directly.

An high or low level of certain substances can be an indication of a certain disorder. It may also be that the person has had a certain disorder in the past.