Interleukin‐5 in growth and differentiation of blood eosinophil progenitors in asthma: effect of glucocorticoids

Abstract

1 There are increased numbers of circulating CD34 + progenitor cells for eosinophils in patients with atopic asthma, with a further increase following allergen exposure or spontaneous worsening of asthma. We investigated the expression of IL-5 and IL-5Ra receptor in circulating CD34 + progenitor cells in allergic asthmatics and the eects of corticosteroids. 2 Using double-staining techniques, up to 50% of CD34 + cells expressed intracellular IL-5, and by RT ± PCR, there was signi®cant expression of IL-5 mRNA. When cultured in a semi-liquid methylcellulose medium, there were more eosinophil colony-forming units grown from asthmatic non-adherent mononuclear cell depleted of T cells in the presence of the growth factors GM-CSF, SCF and IL-3, but not of IL-5. 3 An anti-IL-5Ra receptor antibody and an anti-sense IL-5 oligonucleotide reduced the number of eosinophil colony forming units. No IL-5 mRNA or protein expression on T cells was observed in asthmatics or normal subjects. In the presence of growth factors including IL-5, there were signi®cantly greater colony numbers with eosinophilic lineage grown from either asthmatics or normal subjects. 4 Dexamethasone (10 76 M) suppressed IL-5 mRNA and protein expression in CD34 + cells, and reduced eosinophil colony-forming units in asthmatics, but not in normal subjects. Dexamethasone did not change the expression of IL-5Ra on CD34 + cells. 5 We conclude that there is increased expression of IL-5 on blood CD34+ cells of patients with asthma and that this expression may auto-regulate eosinophilic colony formation from these progenitor cells. Corticosteroids inhibit the expression of IL-5 in circulating CD34 + progenitor cells.

Allergen exposure–induced differences in CD34+ cell phenotype: relationship to eosinophilopoietic responses in different compartments

“…31 Furthermore, BALf CD34 ϩ cells release quite high amounts of IL-5, suggesting that these cells have autocrine multiplication and/or differentiation pathways, which is in line with a previously suggested autocrine differentiation pathway of peripheral blood CD34 ϩ cells in individuals with asthma. 19 In conclusion, our study shows that AW allergen exposure induces an increase in early CD135 ϩ bone marrow hematopoietic progenitors without a simultaneous increase of the total number of bone marrow CD34 ϩ cells. In addition, allergen exposure increases the number of CD34 ϩ cells in BALf, and these CD34 ϩ cells not only can complete their differentiation into eosinophils but also have the capacity to produce eosinophil colonies, proving their ability to multiply.…”

“…Following 8 and 14 days in culture, colonies contained more than 40 cells were counted by using an inverted light microscope as described previously. 19 To confirm the identification of eosinophil colonies on day 14, cells were washed with prewarmed RPMI medium supplied with 0.5% BSA and 20% FCS; cytospins were made and stained by the May-Grünwald-Giemsa method for differential cell counting. In addition, immunocytochemistry for CD34 antigen was performed together with LFB counterstaining and immunocytochemistry for IL-5R␣.…”

Cells isolated from bone-marrow and lungs of allergic BALB/C mice and cultured in the presence of IL-5 are respectively resistant and susceptible to apoptosis induced by dexamethasone

“…Both studies differ from our own, where recombinant IL-5 was present. More recently, Kuo et al have shown that dexamethasone decreases IL-5 mRNA and protein in human circulating CD34+ eosinophil progenitors, but does not decrease expression of IL-5Ra on these cells [36]. In their study, dexamethasone only decreased eosinophil colony formation by CD34+ cells from asthmatic donors.…”

In situ hematopoiesis: a regulator of TH2 cytokine-mediated immunity and inflammation at mucosal surfaces

“…Likewise, in a proof-of-concept study for the development of anti-IL-5 therapies (see below) in human subjects, systemically administered IL-5 stimulated the appearance of increased numbers of circulating CD34 þ /IL-5Ra þ cells. 67 In addition, several groups have reported the increased expression of IL-5Ra on CD34 þ progenitor cells in the bone marrow of atopic asthmatics. 68 This supports the concept that HSPCs in atopic subjects are primed to respond to IL-5 (ref.…”

“…76,77 It has been shown that up to 50% of CD34 þ cells from asthmatic subjects express intracellular IL-5 protein and exhibit high expression of IL-5 mRNA. 67 Further, progeny of Eo/B progenitors in colonies express GM-CSF protein and mRNA, 82 and there is an autocrine GM-CSF-dependent signaling mechanism for Eo/B differentiation mediated through bacterial lipopolysaccharide signaling. 83 In addition, as CD34 þ progenitors undergo ISH in the nasal mucosa of allergic subjects, 59 IL-5, along with IL-9 signaling, can upregulate the surface expression of IL-5Ra during terminal eosinophil differentiation.…”