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    More efficient techniques in the basophil detection


    Basophils were found in human peripheral blood by Paul Ehrlich 140 years ago. These kinds of cells represent <1% of the peripheral blood leukocytes and they have also been identified in other species, which means that they are not just human cells. However, we can see differences and also similarities between human and other species basophils as mice, rabbits or monkeys. But what really are the basophils? is the basophil detection and activation an important research focus? What does it mean to have low basophils? What is basopenia? What is actually relevant in basophil markers in allergic responses?

    In this article we are going to talk about basophil detection by flow cytometry at single cell level and how to apply this technique in order to detect basopenia and basophilia.

    What are basophils?

    We can find five types of white blood cells in our system, which are also called leukocytes: Neutrophils, Lymphocytes (B cells and T cells), Monocytes, Eosinophils and Basophils.

    Basophils are a kind of white blood cells we can find in our system; they are developed in the bone marrow, and they take part in our immune system. However, these blood cells are the least numerous cells in all mammals.

    All blood cells can be found in all our blood system and lymph tissues, which is the reason why we can detect basophils in plasma samples, and they are the responsible of fighting against infections and external pathogens that enter our system.

    As we have mentioned before, basophils are not as abundant as other blood cells, however they have different characteristics that help them have a role in our immune system such as:

    They have a short life, they just last one or two days (which make these basophils difficult to detect and study).

    Basophils just have one nucleolus (they are mononuclear cells.

    They are granulocytes (which means that they have granules attached to them). These small particles called granules have also enzymes that are released when there is an allergic reaction.

    What is the role of basophils in our system?

    We have addressed the main characteristics of these blood cells called basophils.  In this sense, what is the main role of these cells?  Basophils have been widely studied in order to understand their main functions, given that during a long time it was unknown. However, several studies have finally demonstrated that basophils have a similar function than mast cells, and they play an role in immune surveillance

    On the other hand, these cells help preventing blood clotting. Basophils contain heparin. This is a naturally occurring blood-thinning substance. And they also act mediating allergic reactions, releasing histamine when our system has been exposed to a external pathogen. In this sense, basophils take part in the generation of immunoglobulins E (ige).

    In this regard, detecting these basophils and identifying them could definitely help Early diagnosis of type I and II allergies. Thus, as we can access to the detection of basophils in plasma samples, we will be able to apply flow cytometry technique for basophils diagnostic applications.

    Furthermore, there are studies that have shown how these cells also help detecting and fighting early cancer cells (find out more about cancer research).

    Diagnostic applications of basophil determination

    Basophil tests have different diagnostic applications, doctors all over the world uses this kind of test in order to diagnose health issues such as basopenia and basophilia. The levels of basophil cells in our system can change, therefore If we can detect that these levels are low or high, we are able to indicate that we are facing an autoimmune condition, or a blood disorder. In this sense we can ask ourselves what does it mean to have low or high basophils? What is basopenia and basophilia?

    What does it mean to have low basophils?

    As we have addressed before, white blood cells can be found in our immune system, and they are responsible of realizing some enzymes that help our system fighting against pathogens such as virus and bacteria.

    Usually, a normal healthy range is 0 to 3 basophils per microliter of blood, and in this sense, if this level is lower, we can develop infections, allergies, and overactive thyroid gland. We call this clinical condition “basopenia”.

    Therefore, having low basophils is called basopenia. And it is a rare condition that occurs when the production of white blood cells in the bone marrow decreases.

    What is the basophilia?

    Basophilia or is a sign your body is producing too many basophils. Basophilia may be a sign that we have an infection, or it may be a sign of serious medical conditions like leukemia or autoimmune disease.

    Furthermore, high levels of basophils are the reason why we have some symptoms such as sneezing, coughing, or having a runny nose during allergy season or anytime we have contact with an allergen.

    Even though we certainty know that basophilia happens when you have too many basophils, several things can cause this basophil count to increase which make detection and quantification of these basophils interesting in diagnostic and research applications.

    For instance, sometimes, basophilia symptoms are a sign your body is fighting a serious medical condition like hyperthyroidism or cancer. Other times, these symptoms indicate your body is battling a persistent infection or fending off an allergen.

    Basophil  detection and activation techniques

    Basophil detection by flow cytometry: Basophil activation test (BAT)

    The basophil activation test (commonly called BAT) is a test that determine the allergic responses by flow cytometry, thought the activation of markers such as CD63, that are unique markers in order to identify basophil granulocytes.

    Basophil activation tests are able to quantify basophil responses to different allergens cross-linking ige on between 150 and 2000 basophil granulocytes in <0.1 ml fresh blood.

    In this sense, Immunostep have developed BASOSTEP reagents kit for the determination of activation  (basophil detection) upon allergen stimulation by flow cytometry. This test is abl to determine ige-mediated allergic reactions by the analysis of CD63 antigen surface on basophils upon allergen stimulation using flow cytometry.

    BASOSTEP Kit test includes the chemotactic peptide N-formyl-Met-Leu-Phe (fmlp) as positive control and a cocktail of for antibodies for detection and determination of degranulated basophils activation.

    Therefore, BASOSTEP assay is based on in-vitro stimulation of basophils using fmlp as positive control and subsequent flow cytometry analysis of membrane expression of CD63 on basophils after degranulation.

    Why the detection of basophils in plasma samples and whole human blood is important?

    In susceptible people, ige is produced by B cells in response to specific antigens such as foods, pollens, latex, and drugs. This antigen specific (or allergen-specific) ige circulates in the serum and binds to high-affinity ige receptors on immune effector cells such as mast cells located throughout the body.

    Upon subsequent exposure to the same allergen, ige receptors cross-link and initiate downstream signaling events that trigger mast cell degranulation and an immediate allergic response—hence the term immediate hypersensitivity.

    Selection of basophil markers

    The use of basophil detection for diagnostic applications and clinical monitoring of allergies, have recently been of increasing interest. In this regard, it is especially important for the sensitivity and specificity of the clinical results of the BAT test to correctly choose the markers to which we are going to direct our flow cytometry assay.

    For instance, BASOSTEP assay by Immunostep has been developed to detect CD63 antigen on the surface on basophils, but why targeting this CD63 marker In basophils?

    The kit is based on the method described by Sainte-Laudy et al. 1994 where basophil activation by allergens is detected by flow cytometry measured by the increase of CD63 (gp53) at the cellular surface.

    Basophils are known to be an early and abundant source of Th2 cytokines and other mediators of Th2 inflammation.

    Because of the Basophils sensitization with allergen specific ige, they represent a significant effector population in allergic pathogenesis.

    There is also growing recognition of their capacity to modulate adaptive immunity.

    Find out more about the basophil detection upon allergen stimulation by flow cytometry by visiting our website and discover BASOSTEP, an assay that can offer a more specific determination of basophils than other tests, without exposing the patients to the allergens.

    Immunostep offers 3 different solutions of this assay depending on your clinical needs: find out more by contacting us and subscribe to our newsletter for more specific content about cell analysis.


    1. Hoffmann HJ, Santos AF, Mayorga C, et al. The clinical utility of basophil activation testing in diagnosis and monitoring of allergic disease. Allergy. 2015;70(11):1393-1405. Doi:10.1111/all.12698
    2. Keswani T, Patil SU. Basophil activation test in food allergy: is it ready for real-time?. Curr Opin Allergy Clin Immunol. 2021;21(5):442-447. Doi:10.1097/ACI.0000000000000774
    3. Https://www.webmd.com/a-to-z-guides/what-are-basophils
    4. Https://my.clevelandclinic.org/health/diseases/22099-basophilia
    5. Https://onlinelibrary.wiley.com/doi/10.1111/all.14747
    6. Https://my.clevelandclinic.org/health/body/23256-basophils