The human basophil: a new appreciation of its role in immune responses

Leishmanial infection: analysis of its first steps. A review

The first steps in leishmaniasis are critical in determining the evolution of the disease. Major advances have recently been done in understanding this crucial moment. Fundamental research in parasite-vector interaction, parasite biology, insect saliva, and vertebrate host response have shed new light and uncovered a most fascinating and complex moment in leishmaniasis. We review here some of these aspects and we try to connect them in a logical framework.

Expression of cell-surface antigens in acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APL) with M3 (or M3v) morphology is the only AML subtype to date for which morphology and immunophenotype agree. In other words, FAB M3 is interchangeable with a unique marker profile. More precisely, we have finally recognized a surrogate marker profile for leukaemia derived from the (15;17) translocation and expressing PML/RARalpha transcripts. To present this as a new development may come as a surprise to many. After all, the antigen expression pattern of AML-M3 was well recognized for many years: absence or weak expression of HLA-DR, CD117, CD15, CD11b and CD34 in the context of a myeloid phenotype (CD33 and CD13 expression) and frequently associated with moderate to high side-scatter appearance upon flow cytometric evaluation, depending upon the degree of granularity of the leukaemic cells. While partially correct, this established APL phenotype is both flawed and limited in its ability to distinguish APL from other AML subtypes, such as natural-killer-cell AML. Given the availability of phenotype-specific therapy for APL, such as all-trans retinoic acid or arsenic trioxide, failing to diagnose APL or misdiagnosing a case of AML with an APL-like phenotype will result in serious clinical consequences. Faced with this dilemma, we have recently performed a comprehensive immunophenotypic analysis of APL patients entered on Eastern Cooperative Oncology Group trials. Our results give diagnostic power to only three antigens, HLA-DR, CD11a and CD18, all of which are characteristically expressed at low levels by APL cells. Despite some significant antigenic differences (e.g. in CD34 expression), this surrogate marker profile for t(15;17) APL applies to both the M3 and the M3v FAB phenotypes and to all three isoforms of the PML/RARalpha transcript.

Fisetin, a flavonol, inhibits TH2-type cytokine production by activated human basophils

BACKGROUND

Activation of mast cells and basophils through allergen stimulation releases chemical mediators and synthesizes cytokines. Among these cytokines, IL-4, IL-13, and IL-5 have major roles in allergic inflammation.

OBJECTIVE

We sought to determine the potency of flavonoids (astragalin, fisetin, kaempferol, myricetin, quercetin, and rutin) for the inhibition of cytokine expression and synthesis by human basophils.

METHODS

The inhibitory effect of flavonoids on cytokine expression by stimulated KU812 cells, a human basophilic cell line, and freshly purified peripheral blood basophils was measured by means of semiquantitative RT-PCR and ELISA assays. The effects of flavonoids on transcriptional activation of the nuclear factor of activated T cells were assessed by means of electrophoretic mobility shift assays.

RESULTS

Fisetin suppressed the induction of IL-4, IL-13, and IL-5 mRNA expression by A23187-stimulated KU812 cells and basophils in response to cross-linkage of the IgE receptor. Fisetin reduced IL-4, IL-13, and IL-5 synthesis (inhibitory concentration of 50% [IC(50)] = 19.4, 17.7, and 17.4 micromol/L, respectively) but not IL-6 and IL-8 production by KU812 cells. In addition, fisetin inhibited IL-4 and IL-13 synthesis by anti-IgE antibody-stimulated human basophils (IC(50) = 5.1 and 6.2 micromol/L, respectively) and IL-4 synthesis by allergen-stimulated basophils from allergic patients (IC(50) = 4.8 micromol/L). Among the flavonoids examined, kaempferol and quercetin showed substantial inhibitory activities in cytokine expression but less so than those of fisetin. Fisetin inhibited nuclear localization of nuclear factor of activated T cells c2 by A23187-stimulated KU812 cells.

CONCLUSION

These results provide evidence of a novel activity of the flavonoid fisetin that suppresses the expression of T(H)2-type cytokines (IL-4, IL-13, and IL-5) by basophils.

Marked improvement of the basophil activation test by detecting CD203c instead of CD63

BACKGROUND

The flow cytometric basophil activation test by detection of CD63 expression has been developed as an alternative method for in vitro diagnosis of IgE-mediated reactions to various allergens. Despite promising initial studies, the test remains disappointing in terms of sensitivity. CD203c has recently been demonstrated as a specific activation marker of basophils that is rapidly up-regulated after allergen challenge in sensitized patients.

OBJECTIVE

The goal of the present study was to compare basophil activation tests by using either CD203c or CD63 in the diagnosis of immediate-type allergy to latex.

METHODS

Twenty-seven patients (health care workers of our institution) who developed clinical features evocative of allergy after contact with latex were included and classified into two groups. Group 1 (n = 16) comprised true allergic patients who presented with typical signs of immediate allergic reaction associated with a positive skin test (prick test). Group 2 (n = 11) consisted of patients whose clinical history was not typical and had negative skin test. Twelve healthy subjects were also studied as controls. We compared the sensitivity of two triple-staining flow cytometric protocols measuring basophil activation after latex stimulation: CD45-IgE-CD63 and CD45-IgE-CD203c.

RESULTS

The CD203c protocol showed a higher sensitivity than the CD63 protocol (75% vs. 50%). In comparison, latex-specific IgE sensitivity was found to be 69%. Furthermore, the magnitude of the basophil response was significantly higher with CD203c in comparison with CD63. Specificity was 100% for both protocols.

CONCLUSION

Due to superior gating of basophils and a higher range of activation in response to allergen, the basophil activation test is markedly improved by use of CD203c instead of CD63.

Influence of the diluent on the effect of highly diluted histamine on basophil activation

BACKGROUND

In modern pharmaceutical practice, it is common to use purified ethanol and purified water for the preparation of homeopathic dilutions. Hahnemann in 1827 recommended good brandy as a diluent. Brandy contains a lot of accompanying substances in addition to ethanol.

PURPOSE OF THE STUDY

The research question was whether different diluents influence the effectiveness of high dilutions, especially above Avogadro's number. We compared two dilution media to investigate the diluent's influence. Within the limitations of the test-system, the dilution media were as similar to good brandy as possible and like purified ethanol. Dilutions of histamine were prepared with both media. As test-system, we used modified basophil activation in an in vitro cell system. Basophils are activated by anti-immunoglobulin E (anti-IgE). The activation of basophils is inhibited by prior incubation with histamine. The reduction in activation was measured with different dilutions of histamine. The test system used a 3-colour flow cytometric method. The interleukin-3 (IL-3) receptor CD123 was used to identify basophils in the leukocyte mixture. The CD63 surface marker was used for quantification of activated basophils.

RESULTS

With higher concentrations of histamine, we observed inhibition on optimally anti-IgE-stimulated basophil activation with a clear concentration dependency. With low concentrations of histamine (up to 10(-31)), we also observed inhibition of IgE-mediated basophil activation. Differences were observed between the dilution media.

CONCLUSION

The preliminary results support the hypothesis that the dilution medium may influence the effects of high dilutions. This could be of importance for homeopathic pharmaceutical practice as well as for ultra-high dilution experiments. The refined basophil test system proved to be highly sensitive and reliable. Further studies are needed.

Tissue responses against immunoisolating alginate-PLL capsules in the immediate posttransplant period

Alginate-polylysine (PLL) capsules are commonly applied for immunoisolation of living cells for the treatment of a wide variety of diseases. Large-scale application of the technique, however, is hampered by insufficient biocompatibility of the capsules with failure of the grafts as a consequence. Most studies addressing biocompatibility issues of alginate-PLL capsules have focused on the degree of overgrowth on the capsules after graft failure and not on the reaction against the capsules in the immediate posttransplant period. Therefore, capsules were implanted in the peritoneal cavity of rats and retrieved 1, 5, and 7 days later for histological examination and X-ray photoelectron spectroscopy analysis for evaluation of chemical changes at the capsule surface. After implantation, the nitrogen signal increased from 5% on day 0, to 8.6% on day 7, illustrating protein adsorption on the capsule's surface. This increase in protein content of the membrane was accompanied by an increase in the percentage of overgrown capsules from 0.5 +/- 0.3% on day 1 to 3.3 +/- 1.6% on day 7. The cellular overgrowth was composed of monocytes/macrophages, granulocytes, fibroblasts, erythrocytes, multinucleated giant cells, and basophils. This overgrowth was not statical as generally assumed but rather dynamic as illustrated by our observation that at day 1 after implantation we mainly found monocytes/macrophages and granulocytes that on later time points were substituted by fibroblasts. As the inflammatory reaction predictably interfere with survival of encapsulated cells, efforts should be made to suppress activities or recruitment of inflammatory cells. These efforts may be temporary rather than permanent because most inflammatory cells have disappeared after 2 weeks of implantation.

Characterization of mast-cell tryptase-expressing peripheral blood cells as basophils

BACKGROUND

Mast-cell tryptase is a protease with proinflammatory activity, the expression of which by peripheral blood leukocytes (PBLs) has not been fully characterized.

OBJECTIVE

We examined tryptase expression in human PBLs to further characterize this tryptase-expressing cell population for lineage and disease association.

METHODS

PBLs were fixed, permeabilized, stained with antibodies to tryptase and a panel of mast cell- and basophil-specific markers, and analyzed by means of flow cytometry.

RESULTS

Tryptase expression was restricted to a population of cells that stained positive for IgE and negative for the panel of lineage markers (IgE(+), lin(-)). This IgE(+), lin(-) population did not stain for the mast-cell markers Kit or chymase but did stain for the basophil-specific granule proteins recognized by the 2D7 and BB1 mAbs. Per-cell tryptase expression demonstrated a greater than 100-fold range of expression among donors but did not correlate with disease status (asthma or mastocytosis), FEV(1), or serum tryptase concentration. Tryptase was released by purified basophils after anti-IgE activation.

CONCLUSIONS

The phenotype of tryptase-expressing PBLs and their lack of increase in patients with mastocytosis demonstrates that these cells are basophils. Per-cell basophil tryptase expression is highly variable between donors, with some donors expressing levels approaching those of mast cells. As such, anti-tryptase antibodies cannot be used to distinguish these 2 cell types from one another by means of flow cytometry. These results demonstrate that tryptase represents an additional mediator through which basophils may contribute to allergic inflammation.

Monitoring of basophil activation using CD63 and CCR3 in allergy to muscle relaxant drugs

Allergic or pseudoallergic reactions that occur during anesthesia have been increasing for the last few years. To date, the diagnosis of allergy to muscle relaxants remains difficult. In this respect, we developed a flow cytometric method for the study of drug-induced basophil degranulation using CD63 and CCR3. Fifty patients who developed clinical features evocative of allergic reactions immediately after induction of anesthesia were included and classified into two groups. Group 1 (n = 39) comprised true allergic patients, who developed typical signs of shock associated to positive skin testing. Group 2 (n = 11) consisted of patients whose clinical history was not typical and skin testing was negative or nonconclusive. Seventeen control subjects were also studied in this report. We compared data from flow cytometry to skin tests, specific IgE, and histamine release results. Flow cytometry showed a sensitivity of 54%, while that of specific IgE was similar, at 62%. Interestingly, when considering the sensitivity of IgE + CD63 for diagnosis, we reached a sensitivity value of 80%. Of 15 negative results for specific IgE, we found 7 positive CD63 tests, while histamine release gave positive results in only 2 cases. Furthermore, the CD63 protocol showed good specificity (100%). We conclude that our flow cytometry protocol is a promising tool in allergy diagnosis since it is specific and complementary to specific IgE detection.

Do basophils play a role in immunity against parasites?

The link between parasites and eosinophilia has been known for more than a century, although the role of eosinophils in host protection is still an open issue. Much less appreciated, however, is the concurrent systemic induction of a related cell type, the basophil, in parasitized hosts. To date, little is known about the role of basophils in immunity against parasites, but recent evidence points to a possible crucial role in the initiation of T-helper type 2 responses in the host. In this article, we review the current understanding of parasitic infections and basophils and discuss their putative role in immunity.