Use of lipid rafting for the analysis of human basophil activation by flow cytometry

Follow-Up of Venom Immunotherapy on Flow Cytometry and Definition of a Protective Index

BACKGROUND

A major problem of venom-specific immunotherapy (VIT) is the absence of reliable parameters for deciding treatment discontinuation.

AIM OF THE STUDY

Intracutaneous tests (ICTs), the basophil activation test (BAT), specific IgEs (sIgEs) and blocking factor (BF) activity were measured during VIT. We made an evaluation by means of a protective index (PI) including ICT, BAT and BF values.

MATERIAL AND METHODS

A population of 45 patients who had experienced a systemic reaction after an insect sting were tested before VIT (T0), at 1 week (T1w), at 10 weeks (T10w) and at 21 weeks (T21w), and, for a subgroup of 17 patients, at 3-5 years (T3-5y). Basophil activation (expressed in % CD63 and in the area under the curve) and BF activity were measured by flow cytometry using the CCR3/CD63 protocol.

RESULTS

The first 21 weeks of follow-up showed no significant variation in the ICT, sIgE and BAT measurements, except for BAT, by eliminating weak negative anti-IgE responses. In these conditions, the decrease in basophil activation was significant at T10w (p = 0.009) and T21w (p = 0.009). Increased BF activity was also significant at T10w (p = 0.008) and T21w (p = 0.002). The PI threshold calculated from the mean ± 3 standard errors (SE) was 64.8 (14.7 ± 16.7, n = 25) at T0. PI increase was significant at T3-5y (3,430 ± 6,282; p < 0.001).

CONCLUSION

VIT induced a significant decrease in ICT values and basophil activation, along with an increase in serum BF activity, significant after 10 weeks of VIT. Evaluated in a larger population, the PI could represent a new tool for the clinico-biological follow-up of VIT efficacy.

Role of basophils in rheumatoid arthritis (Review)

The T helper (Th)1/Th2 imbalance plays a crucial role in the development of rheumatoid arthritis (RA). It is well known that basophils can affect the Th1/Th2 balance by enhancing the Th2 response, while impairing the Th1 response, which is known to be involved in the development of a number of diseases. However, limited information is available with regard to the role of basophils in RA. Decreased levels of circulating basophils and a dominant Th1 response have been reported in adult patients with RA, while children with juvenile RA have been largely found to have increased levels of circulating basophils and a dominant Th2 response. Furthermore, the circulating basophils in the two conditions have an activated phenotype and are associated with disease activity. In addition, a longitudinal study found the Th2 response was dominant in the early stages of RA, while the Th1 response was dominant in long-term chronic RA. These observations indicate that basophils may be involved in the development of RA by affecting the Th1/Th2 balance, particularly in the early stages of RA. Therefore, targeting basophils may be a novel therapeutic strategy for the treatment of RA; however, further investigation is required.

Basophil activation after nonsteroidal anti-inflammatory drugs stimulation in patients with immediate hypersensitivity reactions to these drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the drugs most frequently involved in allergic reactions of which two main types exist: IgE-mediated and crossintolerance. The diagnosis of crossintolerance reactions is often based on the drug provocation test. The potential value of the basophil activation test (BAT) was evaluated using different basophil markers in the diagnosis of patients with crossintolerance to NSAIDs and cutaneous symptoms. We studied 46 patients with crossintolerance to NSAIDs and 45 tolerant controls. BAT was performed with acetyl salicylic acid, paracetamol, diclofenac, dipyrone, naproxen, and ibuprofen at four different concentrations using CD193 and CD203c as basophil markers and CD63 as activation marker. We compared BAT results using CD193⁺ or CD193⁺ CD203c⁺ for basophil selection and found a significant increase in the stimulation index when using CD193⁺ CD203c⁺ in both patients and controls (P = 0.004 and P = 0.017, respectively). Selection of living cells only produced an increase in basophil stimulation in patients for both CD193⁺ and CD193⁺ CD203c⁺ (P < 0.001 for both), whereas in controls there was no change with CD193⁺ and a decrease with CD193⁺ CD203c⁺ (P = 0.001). We found that CD193⁺ CD203c⁺ increased the percentage of positive cases in patients and controls when compared with CD193⁺. When excluding dead cells, there was an increase of 21.7% in patients and 10% in controls. These results indicate that using CD193⁺ CD203⁺, excluding dead cells, is the best approach for BAT although this test is not recommended for the diagnosis of patients with crossintolerance to NSAIDs owing to its low sensitivity and specificity.

Non-genomic inhibitory effect of glucocorticoids on activated peripheral blood basophils through suppression of lipid raft formation

We investigated the non-genomic effects of glucocorticoids (GCs) on inhibition of plasma membrane lipid raft formation in activated human basophils. Human basophils obtained from house dust mite (HDM)-sensitive volunteers were pretreated with hydrocortisone (CORT) or dexamethasone (Dex) for 30 min and then primed with phorbol 12-myristate 13-acetate (PMA, 10 ng/ml) or HDM (10 µg/ml). The expression of CD63, a basophil activation marker, was assessed by flow cytometry. Membrane-bound GC receptors (mGCRs) were analysed by flow cytometry and confocal laser microscopy. Lipid rafts were assessed using a GM1 ganglioside probe and visualization by confocal laser microscopy. Pretreatment of basophils with CORT (10(-4) M and 10(-5) M) and Dex (10(-7) M) significantly inhibited CD63 expression 20 min after addition of PMA or HDM. The inhibitory effects of GCs were not altered by the nuclear GC receptor (GCR) antagonist RU486 (10(-5) M) or the protein synthesis inhibitor cycloheximide (10(-4) M) (P < 0·05). CORT coupled to bovine serum albumin (BSA-CORT) mimicked the rapid inhibitory effects of CORT, suggesting the involvement of mGCRs. mGCRs were detectable on the plasma membrane of resting basophils and formed nanoclusters following treatment with PMA or HDM. Pretreatment of cells with BSA-CORT inhibited the expression of mGCRs and nanoclustering of ganglioside GM1 in lipid rafts. The study provides evidence that non-genomic mechanisms are involved in the rapid inhibitory effect of GCs on the formation of lipid raft nanoclusters, through binding to mGCRs on the plasma membrane of activated basophils.