Gain-of-function mutations in c-kit, which appear to contribute to mast cell hyperplasia, have been detected in both limited and aggressive forms of mastocytosis, suggesting that other mutations or polymorphisms may contribute to the clinical phenotype. Because addition of interleukin-4 (IL-4) to mast cell cultures is reported to induce apoptosis, the hypothesis was considered that individuals carrying the gain-of-function polymorphism Q576R in the cytoplasmic domain of the α-subunit of the IL-4 receptor (IL-4R) might be relatively resistant to the gain-of-function mutation in c-kit. To assess this possibility, 36 patients with either cutaneous or systemic mastocytosis were studied for association with the Q576R polymorphism. The Q576R polymorphism was found more frequently in those with disease limited to skin and who exhibited lower levels of surrogate disease markers. These data suggest that the Q576R IL-4R α- chain polymorphism may mitigate disease expression and confer a better prognosis in patients with mastocytosis.

Accumulation of excessive numbers of mast cells in tissues is the pathologic basis of mastocytosis. Several distinct clinical presentations of mastocytosis are recognized that differ in their age of onset, physical findings, course, prognosis, and therapy. For example, childhood-onset mastocytosis characteristically is limited to the skin and has a better prognosis than adult-onset disease,1 although a subset has a poorer prognosis because of the coexistence of a hematologic disorder.2 

Mastocytosis is often associated with activating mutations in Kit, the receptor for stem cell factor.3 Such mutations have been identified in the lesional skin of adult patients with indolent as well as aggressive mastocytosis and in children with extensive disease.4-6 As such, the presence of activating c-kit mutations alone are not sufficient to account for different clinical forms of the disease, suggesting that other mutations or polymorphisms are likely to influence the clinical outcome of mastocytosis if they occur in genes important for the regulation of mast cell number.

One such candidate gene is the receptor for interleukin 4 (IL-4R) because IL-4 has been shown to down-regulate the growth and differentiation and induce apoptosis of human mast cells.7-9 Polymorphisms in the IL-4R α-chain (IL-4RA) have been investigated in several allergic and inflammatory diseases. Among these, the gain-of- function polymorphism, Q576R (single-letter amino acid codes), appears to have clinical relevance, because it has been shown to be associated with atopy, severe asthma, and renal allograft rejection.10-12 We thus hypothesized that patients expressing the Q576R IL-4RA polymorphism might be relatively protected from severe mast cell hyperplasia resulting from activating mutations in c-kit and other yet-to-be discovered events that promote mast cell hyperplasia. Patients carrying the Q576R polymorphism do appear to have more limited forms of mastocytosis, suggesting that this polymorphism confers relative protection from adverse events that lead to pathologic mast cell hyperplasia.

Patients

Thirty-six patients with mastocytosis were examined in a study approved by the Institutional Review Board of the National Institute of Allergy and Infectious Diseases. All patients signed an informed consent document. The diagnosis of mastocytosis was based on the demonstration of characteristic skin or bone marrow biopsy findings. Each patient was assigned a category based on the pattern of the disease: cutaneous mastocytosis (n = 13), indolent systemic mastocytosis as evidenced by characteristic mast cell aggregates in the bone marrow (n = 18), and systemic mastocytosis with an associated nonmast cell hematologic disorder (n = 5). The median age at the time of the study for the patients with mastocytosis was 44 years (range, 2-87 years). Fourteen patients (39%) experienced onset of disease at 18 years of age or younger and thus were classified as having childhood-onset disease. Fourteen patients were male. Buffy coat samples from anonymous healthy adult donors were obtained from the Department of Transfusion Medicine at the National Institutes of Health Clinical Center.

Detection of Q576R polymorphism

Total RNA was extracted from peripheral blood mononuclear cells and reverse transcribed to complementary DNA (cDNA) as reported.6 This cDNA was used as a template to amplify a 307-bp product containing the region encoding the IL-4RA Q576R polymorphism by nested polymerase chain reaction (PCR) as described.10 Presence of the polymorphism and its allelic status were determined by direct PCR sequencing using the Big Dye Terminator kit (PE Biosystems, Foster City, CA) and analysis on a capillary automated sequencer (ABI Prism 310 Genetic Analyzer, PE Biosystems).

Determination of tryptase and soluble CD117

Tryptase levels were measured with the UniCAP system (Pharmacia-Upjohn, Peapack, NJ) using monoclonal antibodies (mAbs) B12 for capture and β-galactosidase-G4 for detection as described.13 Soluble CD117 was measured by enzyme-linked immunosorbent assay (ELISA) using the mAbs L6 and L15 as described (Nichirei Diagnostics, Nichirei, Japan).14 All samples were assayed in duplicate.

Statisticalanalysis

Comparisons for statistical significance were performed using the Wilcoxon rank sum (Mann-Whitney U) test. Contingency table analyses were performed by the Fisher exact test. A Pvalue of less than .05 was considered statistically significant.

We first determined the frequency of the IL-4RA Q576R polymorphism in individuals with and without mastocytosis. In a randomly selected population of blood bank donors without mastocytosis, the frequency of individuals who carried the polymorphic R576 allele was found to be 28.6% (4 of 14) with an allelic frequency of 17.9%. These values are consistent with the originally reported frequency of this polymorphism.10 Similarly, in a group of 36 patients with mastocytosis, the overall frequency of the patients carrying the polymorphic R576 allele was found to be 30.6%, with an allelic frequency of 19.4%. Thus, the frequency of the IL-4RA Q576R polymorphism in patients with mastocytosis was not different from that of the general population.

We next compared the frequency of the IL-4RA Q576R polymorphism in patients with mastocytosis assigned to different categories based on disease extent and prognosis. Results revealed that the polymorphism was significantly associated with mastocytosis limited to the skin as compared to those with bone marrow involvement or an associated hematologic disorder. Thus, 9 of 13 (69.2%) of the patients with cutaneous disease alone carried the polymorphism, whereas only 2 of 23 (8.7%) with systemic disease had the polymorphic allele (Table1). The odds ratio for having the mild disease in the presence of the polymorphic R576 allele was calculated to be 23.6 (P < .001; 95% confidence interval, 3.6-153). Further, the association of the polymorphism with milder disease persisted when patients are grouped according to the age at onset of disease. Fewer patients with adult-onset disease were found to have the polymorphism as compared to those with childhood-onset disease (18.2% versus 50%, P = .05); however, the polymorphism was more frequently found in patients with limited involvement in both childhood- and adult-onset disease (Table 1).

Circulating levels of tryptase and soluble CD117 have been proposed as surrogate markers of disease severity and correlate with bone marrow pathology in mastocytosis.14 We therefore also determined the serum tryptase and plasma soluble CD117 levels in 23 patients with or without the polymorphic allele. Consistent with the association found according to the categorization based on clinical presentation, the patients with the polymorphic R576 allele had significantly lower levels of both tryptase and soluble CD117 (Figure1). Thus, patients with mastocytosis who carried the polymorphism had a median serum tryptase level of 22 ng/mL (range, 2-212 ng/mL), whereas the patients with the wild-type gene had a median serum tryptase level of 118 ng/mL (range, 8-596 ng/mL;P = .01). Similarly, median plasma soluble CD117 values were 216 AU/mL (range, 148-753 AU/mL) and 680 AU/mL (range, 179-4755 AU/mL), respectively, for patients with or without the polymorphism (P = .02). No significant difference was found in serum IgE concentrations between the 2 groups.

Fig. 1.

Q576R polymorphism and mastocytosis.

IL-4RA Q576R polymorphism is associated with lower levels of surrogate disease markers, tryptase (A) and soluble CD117 (sCD117) (B), in mastocytosis. Each data point represents the result from one patient. Bars represent median values. AU indicates arbitrary units (1 AU = 1.4 ng); WT, wild type.

Fig. 1.

Q576R polymorphism and mastocytosis.

IL-4RA Q576R polymorphism is associated with lower levels of surrogate disease markers, tryptase (A) and soluble CD117 (sCD117) (B), in mastocytosis. Each data point represents the result from one patient. Bars represent median values. AU indicates arbitrary units (1 AU = 1.4 ng); WT, wild type.

Close modal

In conclusion, this study shows that the presence of the IL-4RA Q576R polymorphism in a patient with mastocytosis is associated with a lower mast cell burden as determined both by extent of clinical disease and by circulating levels of surrogate disease markers. This finding suggests a protective role for IL-4RA Q576R polymorphism in the limitation of tissue mast cell numbers in patients with mastocytosis.

The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked “advertisement” in accordance with 18 U.S.C. section 1734.

1
Kettelhut
BV
Metcalfe
DD
Pediatric mastocytosis.
J Invest Dermatol.
96
1991
15S
18S
2
Travis
WD
Li
CY
Yam
LT
Bergstralh
EJ
Swee
RG
Significance of systemic mast cell disease with associated hematologic disorders.
Cancer.
62
1988
965
972
3
Nagata
H
Worobec
AS
Oh
CK
et al
Identification of a point mutation in the catalytic domain of the protooncogene c-kit in peripheral blood mononuclear cells of patients who have mastocytosis with an associated hematologic disorder.
Proc Natl Acad Sci U S A.
92
1995
10560
10564
4
Longley
BJ
Jr
Metcalfe
DD
Tharp
M
et al
Activating and dominant inactivating c-KIT catalytic domain mutations in distinct clinical forms of human mastocytosis.
Proc Natl Acad Sci U S A.
96
1999
1609
1614
5
Worobec
AS
Semere
T
Nagata
H
Metcalfe
DD
Clinical correlates of the presence of the Asp816Val c-kit mutation in the peripheral blood mononuclear cells of patients with mastocytosis
Cancer.
83
1998
2120
2129
6
Akin
C
Kirshenbaum
AS
Semere
T
Worobec
AS
Scott
LM
Metcalfe
DD
Analysis of the surface expression of c-kit and occurrence of the c-kit Asp816Val activating mutation in T cells, B cells, and myelomonocytic cells in patients with mastocytosis.
Exp Hematol.
28
2000
140
147
7
Oskeritzian
CA
Wang
Z
Kochan
JP
et al
Recombinant human (rh)IL-4-mediated apoptosis and recombinant human IL-6-mediated protection of recombinant human stem cell factor-dependent human mast cells derived from cord blood mononuclear cell progenitors.
J Immunol.
163
1999
5105
5115
8
Xia
HZ
Du
Z
Craig
S
et al
Effect of recombinant human IL-4 on tryptase, chymase, and Fc epsilon receptor type I expression in recombinant human stem cell factor-dependent fetal liver-derived human mast cells.
J Immunol.
159
1997
2911
2921
9
Nilsson
G
Miettinen
U
Ishizaka
T
Ashman
LK
Irani
AM
Schwartz
LB
Interleukin-4 inhibits the expression of Kit and tryptase during stem cell factor-dependent development of human mast cells from fetal liver cells.
Blood.
84
1994
1519
1527
10
Hershey
GK
Friedrich
MF
Esswein
LA
Thomas
ML
Chatila
TA
The association of atopy with a gain-of-function mutation in the alpha subunit of the interleukin-4 receptor [see comments].
N Engl J Med.
337
1997
1720
1725
11
Rosa-Rosa
L
Zimmermann
N
Bernstein
JA
Rothenberg
ME
Khurana Hershey
GK
The R576 IL-4 receptor alpha allele correlates with asthma severity.
J Allergy Clin Immunol.
104
1999
1008
1014
12
Hackstein
H
Kluter
H
Fricke
L
Hoyer
J
Bein
G
The IL-4 receptor alpha-chain variant Q576R is strongly associated with decreased kidney allograft survival.
Tissue Antigens.
54
1999
471
477
13
Schwartz
LB
Sakai
K
Bradford
TR
et al
The alpha form of human tryptase is the predominant type present in blood at baseline in normal subjects and is elevated in those with systemic mastocytosis.
J Clin Invest.
96
1995
2702
2710
14
Akin
C
Schwartz
LB
Kitoh
T
et al
Soluble stem cell factor receptor (CD117) and IL-2 receptor alpha chain (CD25) levels in the plasma of patients with mastocytosis: relationships to disease severity and bone marrow pathology.
Blood.
96
2000
1267
1273

Author notes

Cem Akin, Laboratory of Allergic Diseases, NIAID/NIH, 10 Center Dr, MSC 1881, Bldg 10, Rm 11C205, Bethesda, MD 20892-1881; e-mail: cakin@niaid.nih.gov.

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