From the Guidelines
Reactive lymphocytes on a peripheral blood smear are typically indicative of a broad immune response, such as in the case of infection, autoimmunity, or leukemia/lymphoma 1.
Clinical Significance
- The presence of reactive lymphocytes can be associated with a variety of conditions, including infections, autoimmune disorders, and hematological malignancies.
- In the context of immunobiological conditions, reactive lymphocytes are expected to show an irregular Gaussian curve/smear or one or two peaks/bands in PCR reactions 1.
- This profile is distinct from that of monoclonality, which is characterized by one or two peaks/bands with no Gaussian curve/smear 1.
Diagnostic Considerations
- The identification of reactive lymphocytes on a peripheral blood smear should prompt further investigation to determine the underlying cause of the immune response.
- Additional diagnostic tests, such as flow cytometry, molecular studies, or bone marrow biopsy, may be necessary to establish a definitive diagnosis 1.
- It is essential to consider the clinical context and correlate the laboratory findings with the patient's symptoms, medical history, and physical examination to ensure accurate interpretation of the results.
From the Research
Clinical Significance of Reactive Lymphocytes
The presence of reactive lymphocytes on a peripheral blood smear can be an indicator of various clinical conditions. Some of the key points to consider include:
- Reactive lymphocytes, also known as atypical lymphocytes, can be found in the peripheral blood in response to viral infections, drugs, inflammatory signals, or allergens 2.
- The presence of these cells can be predictive of certain conditions, such as persistent B-cell polyclonal lymphocytosis (PPBL) 3.
- The morphologic features of reactive lymphocytes can be heterogeneous, but certain characteristics, such as mid-sized cells with asymmetrical bilobed nuclei and moderately basophilic cytoplasm, can be more specific to PPBL 3.
- The detection of reactive lymphocytes can be facilitated by computer-assisted diagnosis using multi-object detection networks with large kernels 4.
- Atypical lymphocytes have been observed in a variety of clinical situations, including immune reactions, autoimmune disorders, malignant disease, and infectious mononucleosis 5.
- The evaluation of blood films is an important screening tool for differentiating between reactive and malignant processes, and the optimal lymphocyte number to trigger morphological evaluation of the smear has been found to be around 7×10(9)/L 6.
Predictive Value of Reactive Lymphocytes
The predictive value of reactive lymphocytes for certain clinical conditions is supported by several studies, including:
- A study that found that a peripheral blood lymphocyte count of ≥ 2.375 x 10^9/L was predictive of atypical lymphocytes with a sensitivity of 68.42% and specificity of 82.8% 2.
- A study that found that the presence of binucleated lymphocytes with specific morphologic features was predictive of PPBL 3.
- A study that found that the use of a multi-object detection network with large kernels could achieve a high accuracy in detecting reactive lymphocytes 4.
- A study that found that the evaluation of lymphocyte morphology could be a useful screening tool for differentiating between reactive and malignant processes, with a sensitivity of 0.9 and specificity of 0.59 6.
Morphologic Features of Reactive Lymphocytes
The morphologic features of reactive lymphocytes can be variable, but some common characteristics include:
- Increased size and active DNA synthesis 5.
- Mid-sized cells with asymmetrical bilobed nuclei and moderately basophilic cytoplasm 3.
- Monocytoid or hyperbasophilic cells, which can be systematically found in PPBL patients 3.
- Heterogeneous mixture of cell types, indicating a polyclonal immune response to antigenic stimulation 5.