From the Guidelines
Reactive lymphocytes are a type of white blood cell that has become activated in response to an infection, inflammation, or other immune challenges, and their presence typically indicates that the body is fighting an infection or other immune-related condition. When seen on a blood smear, these cells appear larger than normal lymphocytes, with abundant cytoplasm that may be darker blue and sometimes contain vacuoles, as described in the context of immunobiological conditions 1. The nucleus may be irregular or indented. Reactive lymphocytes can be expected in specimens with numerous reactive lymphocytes, showing a more or less complete Gaussian distribution in Ig/TCR profiles, whereas a dominant immune response might create reproducible peaks or bands 1.
Key Characteristics of Reactive Lymphocytes
- Appear larger than normal lymphocytes
- Abundant cytoplasm that may be darker blue
- May contain vacuoles
- Irregular or indented nucleus
- Typically indicate an active immune response to infection, inflammation, or other immune challenges
Reactive lymphocytes typically indicate that the body is fighting an infection, most commonly viral infections like Epstein-Barr virus (infectious mononucleosis), cytomegalovirus, hepatitis, or HIV, as well as responses to certain medications, vaccinations, or autoimmune conditions. Finding reactive lymphocytes in a blood test is not necessarily concerning by itself but indicates an active immune response. The presence of these cells usually resolves once the underlying condition is treated or resolves on its own. If reactive lymphocytes are reported on blood work, the healthcare provider will consider this finding alongside symptoms and other test results to determine if further investigation or treatment is needed, taking into account the latest guidelines and research, such as those related to chronic lymphocytic leukemia/small lymphocytic lymphoma 1.
Clinical Implications
- Indicate an active immune response
- Usually resolve with treatment or resolution of the underlying condition
- Healthcare providers consider this finding alongside other symptoms and test results to determine the need for further investigation or treatment
- Latest guidelines, such as those for chronic lymphocytic leukemia/small lymphocytic lymphoma, inform the interpretation of reactive lymphocytes in the context of specific conditions 1
From the Research
Definition of Reactive Lymphocytes
- Reactive lymphocytes refer to a type of lymphocyte that is activated in response to an antigen or infection [ 2 ].
- These cells play a crucial role in the immune system, helping to protect against infection and disease [ 3 ].
Characteristics of Reactive Lymphocytes
- Reactive lymphocytes can be identified through flow cytometry markers of inflammation, such as CD38+ and HLA-DR+ [ 2 ].
- They can also be distinguished from other types of lymphocytes based on their surface markers and functional characteristics [ 4 ].
Role of Reactive Lymphocytes in Disease
- Reactive lymphocytes have been implicated in the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) [ 3 ].
- They can also play a role in the immune response to infection, such as COVID-19 [ 2 ].
- The presence of autoantibodies, which are produced by reactive lymphocytes, can be an important diagnostic tool for autoimmune diseases [ 5 ].