Background Information of Reactive/Atypical Lymphocytes
Reactive lymphocytes are typically larger in size due to viral-antigen stimulation. They can often grow up to three times the size of a RBC and may vary with shape. Viral illnesses are one of the most common causes for an increase in reactive lymphocytes. When a virus (Hepatitis C/Cytomegalovirus) is detected, the body immune system will respond by sending lymphocytes to maintain the viral load and preventing further immune damage. Upon stimulation from the virus, the lymphocytes will grow in size and activate "granules" to "sterilize" the viral functions.
They can also be present as a result of drug reactions (such as phenytoin), immunisations, radiation, hormonal causes (such as stress and Addison's disease) as well as some auto-immune disorders (such as rheumatoid arthritis). Although the trigger can be different for each individual person, the body sees the moelcules within the medications as a foreign antigen
Reactive/Atypical lymphocytes are significantly larger (up to ~3 times) than erythrocytes and may vary (mostly round) in shape. Usually their cytoplasm is scanty and stained dark blue with some purple granules. The dark purplish staining nucleus may cover atleast 70% of the cytoplasm.