Basophils - Characterization, Markers and Antibodies

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Overview

Basophils are a specific type of leukocyte called granulocytes, which are characterized by large cytoplasmic granules that can be stained by basic dyes and a bi-lobed nucleus, being similar in appearance to mast cells, another type of granulocyte. Basophils are the least common granulocyte, making only 0.5% of the circulating blood leukocytes, and have a short life span of only 2-3 days.

Basophils are derived from granulocyte-monocyte progenitors in the bone marrow; where basophil precursors and mast cell precursors arise from an intermediate bipotent basophil-mast cell precursor (Arinobu et al. 2005 and Arinobu et al. 2009). Table 1 shows the markers associated with the different lineage cell types. To view antibodies available to these markers simply click on the marker.

Data from Min et al 2012.

There are many factors which effect lineage direction, such as growth and transcription factors, where the level and the timing of these factors make a difference to the differentiation of the cell. CCAAT-enhancer-binding protein α, GATA-2 and Ikaros have been linked to basophil-mast cell lineage determination (Arinobu et al. 2005 and Min et al. 2012).

In response to inflammatory signals released during the initial stages of infection the number of basophils dramatically increases and they are recruited to the site of infection. It is thought that IL-3 may aid basophil recruitment (Shen et al. 2008). IL-3 has also been shown to prime basophils to increase IL-4 secretion, which basophils can do immediately upon activation. Thymic stromal lymphopoietin has also been seen as a key regulator of basophil development and activation and, along with IL-3, may confer many different functions to basophils (Siracuca et al. 2011 and Min et al. 2012). However there are many factors that affect basophil development, activation and function (Min et al 2012), this includes the classical activation of basophils when antigen binds and cross links FcƐRI and IgE that are expressed on the surface of the basophil (Solol and Medzhitov 2010). This then leads to the activation of the SyK-mediated siganaling cascade and results in the production of cytokines, chemokines and the release of preformed factors via a process called degranulation (Prussin and Metcalfe 2006).

Studies have shown that basophils can have a number of functions such as antigen presentation, stimulation and differentiation of CD4⁺ T cells in to T helper type 2 effectors cells (via IL-4 secretion) and initiators and regulators of the adaptive immune response (Solol and Medzhitov 2010). However it is the process of degranulation for which basophils are most renowned. Degranulation of the basophil results in the release of vasoamines and eicosanoids such as histamine and leukotriene C4 the purpose of which is pathogen removal by increasing vascular permeability; however this also leads to the characteristic symptoms of an allergic response (Schroeder 2009).

There are many unanswered questions in regards to the development, activation and role of basophils; further studies are required to determine any potential of basophils as a therapeutic agent owing to its ability to induce Th2 immune response.

Basophils can be identified by the expression of certain markers, which is consistent between humans and mice, refer to Table 2. To view antibodies available to these markers simply click on the marker.

Data from Schroeder 2009, Hida et al 2009 and Heneberg 2011.

References

• Arinobu Y et al. (2009). Origin of basophils and mast cells. Allergol Int. 58, 21-28.
• Arinobu Y et al. (2005). Developmental checkpoints of the basophil/mast cell lineages in adult murine hematopoiesis. Proc Natl Acad Sci USA. 102, 18105-18110.
• Heneberg P. (2011). Mast cells and basophils: Trojan horses of conventional lin- stem/progenitor cell isolates. Cur Pharm Design. 17, 3753-3771.
• Hilda S et al. (2009). Fc receptor gamma-chain, a constitutive component of the IL-3 receptor, is required for IL-3-induced IL-4 production in basophils. Nat Immunol. 10, 214-222.
• Min B et al. (2012). Understanding the roles of basophils: breaking dawn. Immunol. 135, 192-197.
• Prussin C and Metcalfe DD. (2006). IgE, mast cells, basophils, and eosinophils. J allergy Clin Immunol. 117,S450-S456.
• Schroeder JT. (2009). Basophils beyond effector cells of allergic inflammation. Adv Immunol. 101, 123-161.
• Shen T et al. (2008). T cell-derived IL-3 plays key role in parasite infection-induced basophil production but is dispensable for in vivo basophil survival. Int Immmunol. 20, 1201-1209.
• Siracuca MC et al. (2011). TSLP promotes interleukin-3-independent basophil haematopoiesis and type 2 inflammation. Nature. 477, 229-233.
• Solol CL and Medzhitov R. (2010). Emerging functions of basophils in protective and allergic immune responses. Musocal Immunol. 3, 129-137.