Opinion Article Int Arch Allergy Immunol 2008;146:177–189 Received: June 25, 2007 DOI: 10.1159/000115885 Accepted after revision: October 18, 2007 Published online: February 11, 2008 Diagnostic Tests Based on Human Basophils: More Potentials and Perspectives than Pitfalls a a b d e A.L. de Weck M.L. Sanz P.M. Gamboa W. Aberer J. Bienvenu c f h c e g M. Blanca P. Demoly D.G. Ebo L. Mayorga G. Monneret J. Sainte-Laudy a b c University of Navarra, Pamplona , Hopital Basurto, Bilbao , and Carlos Haya Hospital, Malaga , Spain; d e f g University of Graz, Graz , Austria; Centres Hospitaliers Universitaires, L y o n , Montpellier and L i m o g e s , F r a n c e ; h Department of Immunology, University of Antwerp, Antwerp , Belgium Key Words sons to deprive allergic patients of clinically indicated BAT, -Basophil activation ؒ Drug allergy ؒ Flow cytometry ؒ which can be performed reliably by any laboratory with al .Food allergy ؒ Insect venoms ؒ ␤ -Lactams ؒ Latex ؒ lergy and flow-cytometric capacity and expertise Myorelaxants ؒ NSAID Copyright © 2008 S. Karger AG, Basel Abstract Introduction For the diagnosis of allergy, cellular basophil activation tests (BAT), e.g. histamine or sulfidoleukotriene release tests, have In a recent issue of this Journal an opinion paper was long been introduced, but the expression of basophil acti- devoted to diagnostic tests in allergy based on human vation markers such as CD63 and CD203c detected by flow basophils [1] . Although reviewing first many publica- cytometry has attracted more recent attention. A recent tions about histamine release as an outcome of basophil opinion paper in this Journal has stressed not only the po- activation, the main discussion and criticisms of this pa- tential but also the possible pitfalls of flow-cytometric BAT. per focus on the flow-cytometric basophil activation test We have applied clinical validation of various BAT in various (BAT), which has recently attracted increased attention. ways for several years, and our experience shows that these The overall picture is strongly influenced by the expe- new technologies have more potentials and perspectives rience gained with anti-IgE- and allergen-induced hista- than pitfalls. A comprehensive review of clinically validated mine release. In a number of ways, expression of basophil studies on allergy to aeroallergens, insect venoms, latex, activation markers, particularly when applied to diag- food allergens and drugs, e.g. myorelaxants, ␤ -lactams, pyr- nostic clinical evaluation of basophil activation, obeys azolones and non-steroidal anti-inflammatory drugs, as well different rules, and a number of pitfalls are simply coun- as chronic urticaria shows clearly that even with different teracted by our long clinical experience with such tests. protocols, reproducible and meaningful results can be ob- The above-mentioned opinion paper [1] also nourishes tained. Although the available technologies may still be op- the general impression that the diagnostic use of flow- timized and better standardized, there are no serious rea- cytometric BAT is plagued with many unresolved ques- © 2008 S. Karger AG, Basel Correspondence to: Prof. Alain de Weck 1018–2438/08/1463–0177$24.50/0 Beaumont 18 Fax +41 61 306 12 34 CH–1700 Fribourg (Switzerland) E-Mail [email protected] Accessible online at: Tel. +41 26 424 6910, Fax +41 26 424 6911 www.karger.com www.karger.com/iaa E-Mail [email protected] Discordant 6,000 100 5,000 80 4,000 60 3,000 40 2,000 sLT (pg/ml) 1,000 20 Histamine release (%) 0 0 0 50 100 0 50 100 a Basophil activation (%) b Basophil activation (%) Fig. 1. Dissociation of basophil activation outcomes in some individuals. Despite overall correlation between skin prick 250 100 tests, sLT (CAST), histamine release and basophil activation (CD63; % = % of acti- 200 80 2 vated cells), individual patients may show 150 60 total dissociation between these outcomes. Data for peach-allergic patients and rPru 100 40 SPT (mm ) p 3 allergen [data from ref. 71 ]. nPru p 3: 50 20 correlation between BAT and CAST ( a ; r = Histamine release (%) 0.39); BAT and the histamine release test 0 0 b 0 50 100 0 2,000 4,000 6,000 ( ; r = 0.66); BAT and the skin prick test c d (SPT; c ; r = –0.35), and CAST and the his- Basophil activation (%) sLT (pg/ml) tamine release test ( d ; r = 0.49). tions and that it should be reserved for the time being to parameters comprehensively studied during histamine basophil-experienced laboratories. release form the basis of the test outcome, independently I n our opinion, some points need to be readdressed of the final test readout. Promoting cellular tests for the to complete the discussion. First, the clinical issues are evaluation of IgE-mediated sensitization has the caveat of discussed in a comprehensive review. More technical is- introducing a number of interrelated variables’. As a mat- sues and controversies are addressed in a following paper ter of fact, and as discussed in greater detail elsewhere [2] , [2] . Readers specifically interested in flow-cytometric the various test readouts do not strictly follow the rules BAT are also referred to some recent reviews [3–10] . established for histamine release: a number of differences in their activation cascades and regulation have been well documented [11–19] . Mechanisms of Basophil Activation These differences probably explain why in clinical practice, although often correlated, the various outcomes The mechanisms of IgE-receptor-mediated activation may occur independently from each other in some indi- and the subsequent transmission of signals leading to the viduals ( fig. 1 ). release of various mediators such as histamine, LTC4 For example, in a number of individuals and accord- (sLT) and lymphokines, e.g. interleukin (IL)-4 and IL-13, ing to the mode of activation, expression of CD63, LTC 4 have been well described [1] ( fig. 1 ). However, the expres- production and histamine release may be entirely disso- sion mechanisms of various membrane proteins, which ciated for the same allergen concentration ( fig. 2 ). In ad- are the basis of diagnostic BAT, as well as the various dition, for in vitro IgE-mediated reactions, the expression mechanisms of non-IgE-mediated activation have not yet of CD63 is much more sensitive to the external Ca 2+ con- 2+ been differentiated, leading to the impression that the centration than LTC4 production, and this relative Ca same quantitative and qualitative rules may apply to the sensitivity varies from one individual to another. This various outcomes of basophil activation (e.g. CD63/ has led in some circumstances to the paradoxical finding CD203c expression, histamine release, LTC4 and lym- of a control negative BAT but positive sLT (CAST assay) phokine formation). Indeed, the authors [1] state that ‘the [Sanz, unpubl. data]. Even the expression of two different 178 Int Arch Allergy Immunol 2008;146:177–189 de Weck et al. Discordant 100 100 75 75 50 50 Basophil activation (%) 25 Basophil activation (%) 25 0 0 0 25 50 75 100 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 a HRT (%) b sLT (pg/ml) Fig. 2. Dissociation between CD63 expression, histamine release and LTC 4 production. Despite strong overall correlation between CD63 expression, histamine release and sLT production (CAST), a sizeable number of pa- tients show total dissociation between these outcomes. Data from patients allergic to aeroallergens (house dust mite d 1 and Lolium perenne ) [data from ref. 26 ]. HRT = Histamine release test. a r = 0.79, p ! 0.001, n = 144. b r = 0.7, p ! 0.001, n = 180. membrane markers, CD63 and CD203c, obeys different included. For some allergens, e.g. food, enrolment of rules and regulations [20, 21] . atopic patients is required, i.e. patients with IgE to aeroal- One must therefore be careful when extrapolating lergens but negative to challenge with the food allergen general conclusions drawn from experience gained with tested. Many of these studies have been reviewed recent- histamine release to other BAT, a point more extensively ly [8–10] . Herewith, tables 1–7 summarize the results of discussed elsewhere [2] . validated clinical studies performed with various aller- gens such as inhalant allergens [25–33] ( table 1 ), hyme- noptera venoms [34–56] ( table 2 ), latex [57–63] ( table 3 ), Clinical Issues in the Diagnostic Use of BAT food [64–80] ( table 4 ) and drugs [81–125] ( tables 5–7 ). The techniques applied are also indicated. In our opin- In addition to the large number of anecdotal studies at ion, these studies demonstrate the diagnostic utility of the beginning of the BAT era in the 1990s [22–24] , during BAT for a number of clinical indications. the past 5 years, a large number of clinically validated Since some specific questions or criticisms have been studies have been published in peer-reviewed and highly raised [1] about some of these studies, we feel it is appro- ranked journals that focus on clinical allergy. Most of priate to address them in more detail. these publications emerged from European groups. Clin- ical studies encompassing at least 15–20 confirmed aller- gic patients were considered validated, demonstrated by Clinical Indications of BAT compelling history and/or provocation tests as well as other positive skin tests and/or allergen-specific IgE for Hymenoptera Allergy example. In addition, at least 10, non-allergic controls The utility of BAT in hymenoptera venom hypersen- negative to skin tests and other allergy diagnostic tests sitivity [34–56] has been confirmed hitherto by many with no history of aeroallergen sensitization should be more than the two studies quoted by Kleine-Tebbe et al.