Reactive lymphocyte

Close-up of a reactive lymphocyte.

A reactive lymphocyte is a type of lymphocyte that has been activated in response to an antigen. These cells are typically larger than normal lymphocytes and exhibit a variety of morphological changes. Reactive lymphocytes are often seen in the context of viral infections, such as infectious mononucleosis, and other immune responses.

Morphology

Reactive lymphocytes are characterized by their increased size, often measuring 12-30 micrometers in diameter. They have abundant cytoplasm, which can appear basophilic and may contain vacuoles. The nucleus of a reactive lymphocyte is often irregularly shaped, with a coarse chromatin pattern. The nucleoli may be prominent, and the nuclear membrane can be indented or folded.

Causes

Reactive lymphocytes are typically seen in response to:

• Viral infections such as Epstein-Barr virus (EBV), cytomegalovirus (CMV), and HIV.
• Bacterial infections like tuberculosis and brucellosis.
• Autoimmune disorders such as systemic lupus erythematosus (SLE).
• Drug reactions and allergic reactions.

Clinical Significance

The presence of reactive lymphocytes in a blood smear can be an important diagnostic clue. In the context of infectious mononucleosis, for example, the presence of atypical lymphocytes is a hallmark finding. Reactive lymphocytes can also be seen in other conditions, and their presence should be interpreted in conjunction with clinical findings and other laboratory tests.

Related Pages

• Lymphocyte
• Infectious mononucleosis
• Epstein-Barr virus
• Cytomegalovirus
• Immune system