Abstract The immune function of peripheral
mono-nuclear cells (MNC) in patients with endemic
arsenic-induced Bowen’s disease (BD) was investigated. Many
cytokines and immune-related factors were determined
in the present study. Interleukin-1
β and TNF-α
pro-duction was used as an indicator of
monocyte/macro-phage function. Il-2 and sIL-2R production was used
as an indicator of lymphocyte activation. The release
of sCD4 and sCD8 was used as an indicator of
activa-tion of respective T-cell subpopulaactiva-tions. Producactiva-tion of
IFN-
γ and IL-2 reflected the cellular effector function
of helper T-cells type 1. In vivo cell-mediated immunity
was also assessed by estimation of the percentage of
T-cells in peripheral blood MNC and the nonspecific
de-layed-type hypersensitivity (DTH) response to
2,4-dini-trochlorobenzene (DNCB). Both assays revealed
de-pressed cell-mediated immunity in BD. Compared with
healthy controls, spontaneous and PHA-induced IFN-
γ
and TNF-
α production was significantly decreased in
BD whereas spontaneous release of IL-2, sCD4 and
sCD8 was significantly increased. Although PHA
stim-ulation increased IL-2 release, the expression of IL-2R
α and β chains and the release of sIL-2R were not
pro-portionately increased in BD. In addition,
IL-2-medi-ated [
3H]-thymidine incorporation by MNC in patients
with BD was significantly decreased. These findings
suggest that the defective cell-mediated immune
func-tion in BD is due to impairment of membrane IL-2R
expression in lymphocytes after stimulation.
Key words T lymphocytes · Tumor immunity · IL-2
receptor · Bowen’s disease
Introduction
An endemic occurrence of skin cancers due to high
con-centrations of arsenic in artesian well water in a limited
area of the southwest coast of Taiwan has been reported
[1]. Arsenical skin cancers in the endemic area include
Bowen’s disease (carcinoma in situ), basal cell carcinoma,
squamous cell carcinoma and their various combinations.
In animals, the carcinogenic nature of arsenic has not yet
been reliably and consistently demonstrated [2]. Chronic
arsenical poisoning in the inhabitants of an area such as
the above may, however, provide a human model of
natu-rally occurring chemical carcinogenesis. Our previous
in-vestigations have demonstated a decrease in
PHA-in-duced [
3H]-thymidine incorporation by peripheral
mono-nuclear cells (MNC) in arsenic-induced Bowen’s disease
(BD) [3] as well as a considerable decline in the density of
Langerhans cells, as compared with normal epidermis [4].
These findings indicate defective cell-mediated immunity
in these patients.
It is not inconceivable that the host response to
malig-nant tumors is primarily cell-mediated. Delayed-type
hy-persensitivity (DTH) response is induced by helper T-cell
type 1 (Th1) and the status of the nonspecific
cell-medi-ated immune response has been measured in response to
2,4-dinitrochlorobenzene (DNCB) [5]. Patients with BD
and squamous cell carcinoma, but not those with basal
cell carcinoma, show an impaired response to DNCB [6],
thus implicating depressed cell-mediated immunity in some
Hsin-Su Yu · Kee-Lung Chang · Chia-Li Yu ·
Ching-Shuang Wu · Gwo-Shing Chen · Ji-Chen Ho
Defective IL-2 receptor expression in lymphocytes
of patients with arsenic-induced Bowen’s disease
Received: 18 September 1997 / Received after revision: 19 August 1998 / Accepted: 27 August 1998
O R I G I N A L PA P E R
H.-S. Yu (쾷) · G.-S. Chen
Department of Dermatology, Kaohsiung Medical College, 100 Shin Chuan 1st Road, Kaohsiung, Taiwan,
Republic of China
Tel. +886-7-3220186; Fax +886-7-3234070; e-mail: [email protected]
K.-L. Chang
Department of Biochemistry, Kaohsiung Medical College, Kaohsiung, Taiwan, Republic of China
C.-L. Yu
Department of Medicine and Institute of Molecular Medicine, National Taiwan University College of Medicine,
Taiwan, Republic of China C.-S. Wu
School of Medical Technology, Kaohsiung Medical College, Kaohsiung, Taiwan, Republic of China
J.-C. Ho
Department of Dermatology, Chang Gung Memorial Hospital, Kaohsiung, Taiwan, Republic of China
skin cancer patients. Cytokines of Th1 cells, such as IFN-
γ
and IL-2, have been shown to be essential modulators of
the cell-mediated immune response. T lymphocyte
activa-tion, proliferation and differentiation are critically
depen-dent on the presence of IL-1 and IL-2 [7]. TNF-
α
,
re-leased mainly from monocytes/macrophages, is a
cyto-toxic molecule for a broad spectrum of tumor cells [8, 9].
Defects in the production of certain cytokines have
been reported in patients with various solid tumors such
as melanoma [10], colorectal cancer [11], gynecological
carcinomas [12], and nasopharyngeal carcinoma [13]. It is
believed that certain soluble molecules of membrane
pro-teins, such as sIL-2R, sCD4 and sCD8, are released by
ac-tivated T lymphocytes and serve as significant
immunoreg-ulatory molecules [14–16]. Recent studies have revealed
an increase in sCD4 and sCD8 production in
nasopharyn-geal carcinoma [13] and sIL-2R, sCD4 and sCD8 levels in
melanoma [17]. Accordingly, release of both cytokines
and soluble membrane molecules can be used as indicators
of the status of the cellular immunity in tumor patients.
In the present study, to assess the immune status of
BD patients, we monitored the DTH response after
ap-plication of DNCB, and determined the plasma sIL-2R
levels, the percentage of each lymphocyte population
(T-cells, activated T-cells and B-cells) and T-cell
subpop-ulation (T-helper cells and T-cytotoxic/suppressor cells),
Th1 cytokines (IFN-
γ
, TNF-
α
, IL-2), the T-cell-activating
monokine (IL-1
β
), and soluble T-cell surface molecules
(sIL-2R, sCD4, sCD8) in these patients, and evaluated the
expression of IL-2R on lymphocytes. Our results suggest
that a defect in IL-2 receptor expression plays an important
role in the immune dysfunction of arsenic-induced BD.
Materials and methods
Selection of patients
All 16 patients with BD were selected from an endemic area in the southwest coast of Taiwan. The mean age of the patients was 68.4 ± 6.5 years (range 61–77 years). The mean age of onset in these patients was 62.8 ± 8.0 years (range 54–74 years) and the av-erage number of lesions was 9.0 ± 4.7 (range 2–14). The exposure time to arsenic in these patients was estimated at more than 20 years and no extracutaneous tumors were found. The average estimated level of arsenic in the water ingest patients in the endemic area was 7.3 ×106ppm. Groups of 16 age- and sex-matched healthy
volun-teers from the endemic area (N-BD controls) and a nonendemic ar-eas (normal controls) were selected. The mean urinary arsenic lev-els in the BD patients and in the N-BD controls and normal controls were 201.1 ± 57.6, 75.5 ± 39.1 and 63.4 ± 29.7 ng/ml, respectively, as determined by atomic absorption spectrophotometry. None of the patients had been medically treated before the study.
Induction of contact sensitization
Measurements of DTH response were conducted using a previ-ously reported method with modification [18, 19]. Briefly, DNCB (Sigma Chemical, St. Louis, Mo.) was diluted to 0.1% in acetone and applied to the upper back epicutaneously using Finn chambers (Epitest, Helsinki) for 24–48 h. After 14 days, the same skin site was challenged with 0.01% DNCB. Only intense cutaneous re-sponses (such as erythema, edema and/or vesicle formation) at the treated site were considered to be positive.
Determination of sIL-2R levels in plasma
Plasma sIL-2R levels were determined using a sandwich enzyme immunoassay (T Cell Diagnostics, Cambridge, Mass.) according to the manufacturer’s instructions.
Isolation of MNC
MNC were isolated from heparinized venous blood after centrifu-gation at 300 g for 30 min over a Ficoll-Hypaque cushion (specific gravity 1.077) as reported previously [20].
Flow cytometric determination of the percentages of lymphocyte populations and subpopulations
The percentages of lymphocyte populations and subpopulations in MNC were determined according to the method of Sindern et al. with modification [21]. Briefly, freshly obtained MNC (1.0 ×106 cells/
ml) in 10% fetal bovine serum in RPMI-1640 medium (GIBCO, Gaithersburg, Md; 10% FBS-RPMI) were double-stained with an-tibodies against CD3-FITC/HLA-DR-PE (for activated T-cells) (Becton and Dickinson, San Jose, Calif.) or against CD4-FITC/ CD8-PE (for T-helper cells and T-cytotoxic/suppressor cells) (Bec-ton Dickinson) in an ice-bath for 30 min. After washing twice with PBS, pH 7.2, the percentages of positively stained cells were analysed in a flow cytometer (FACScan, Becton Dickinson).
Preparation of spontaneous
and mitogen-stimulated MNC culture supernatants
The concentration of MNC was adjusted to 2.5 ×106cells/ml in
10% FBS-RPMI. Then 0.5 ml 10% FBS-RPMI (spontaneous) or 0.4 ml 10% FBS-RPMI and 0.1 ml phytohemagglutinin L form (PHA, 10 µg/ml, Sigma) (PHA-induced) was added to each tube in triplicate. The mixture was incubated at 37° C in an atmosphere comprising 5% CO2and 95% air for 48 h, then centrifuged at
2000 rpm for 10 min and the cell-free supernatants stored at –20° C.
Measurement of cytokines and soluble T-cell surface antigens in culture supernatants
Cytokines and soluble T-cell surface antigens were determined us-ing commercially available ELISA kits. They were assayed usus-ing colorimetric enzyme immunoassays according to the manufacturer’s instructions. The cytokines and antigens determined included: IL-1β, IL-2, TNF-αand IFN-γ(Quantikine, R&D System, Minneapo-lis, Minn.), and sIL-2R (T Cell Diagnostics), sCD4 and sCD8 (T Cell Sciences, Woburn, Mass.).
Measurement of recombinant human IL-2-induced [3H]-thymidine incorporation by MNC
The uptake of [3H]-thymidine by MNC induced by recombinant
human IL-2 (rIL-2, Biosource, Camarillo, Calif.) was measured using a modified version of a method reported previously [22]. Briefly, 0.05 ml of a suspension of MNC (2 ×106cells/ml) was
placed in each well of a microtiter plate in triplicate. Then 50 µl 10% FBS-RPMI or 50 µl rIL-2 (6 U/µl) was added to each well. The mixture was incubated at 37° C in an atmosphere comprising 5% CO2and 95% air for 72 h. After incubation, each microwell was
pulsed with 0.5 µCi (specific activity 6.7 Ci/mmol) methyl[3
H]-thymidine (Dupont, Boston, Mass.) in a volume of 10 µl for 6 h. Then the cells were harvested and the radioactivity was measured in a liquid scintillation counter (Minax-B Tri-Carb 4000 series, Packard, Gowners Grove, Ill.)
Determination of IL-2R αchain and βchain on MNC
The expression of IL-2R αchain and βchain on MNC was assessed according to the method of Kierszenbaum and Szteins [23]. Briefly, freshly obtained MNC in 10% FBS-RPMI (1.0 ×106cells/ml) were
stimulated with PHA (10 µg/ml) for 3 days. Then they were stained with antibodies against CD25-FITC (for p55) and against CD122-PE (for p75) (Becton Dickinson) in an ice-bath for 30 min. After wash-ing twice with PBS buffer, the stained cells were determined in a flow cytometer. Mean fluorescence intensity (MFI) was used as a measure of the expression of IL-2R αand βchains on T cells. Statistical analysis
All values presented are means ± SD. Statistical significance of differences was assessed using the unpaired Student’s t-test be-tween the different groups while the comparisons bebe-tween the per-centages of lymphocyte populations and subpopulations among the BD patients, normal controls and N-BD controls were analysed us-ing Student’s t-test. A P-value of < 0.05 was considered as statis-tically significant.
Results
Low DTH response after DNCB challenge
was observed in BD patients
All of the studied subjects showed a positive response to
the epicutaneous application of 0.1% DNCB. However,
only BD patients showed a negative response to challenge
with 0.01% DNCB. Apparently, the DTH response in BD
patients was weaker than in controls.
Plasma sIL-2R levels in BD patients were similar
to the levels in normal controls
There were no significant differences in sIL-2R levels in
plasma among BD patients (61.3 ± 5.2 pmol/l), normal
controls (57.4 ± 3.0 pmol/l) and N-BD controls (51.5 ±
5.3 pmol/l).
The percentages of T-cells and T-helper cells
were decreased and the percentage of B-cells
was increased in BD patients compared with controls
As shown in Table 1, the percentages of cells and
T-helper cells (46.9 ± 18.8% / 19.5 ± 5.5%) in BD patients
were significantly lower (P < 0.02) than in normal
con-trols and N-BD concon-trols (63.1 ± 12.7% / 31.4 ± 5.7% and
68.6 ± 1.6% / 39.6 ± 1.8%, respectively). The percentage of
B-cells (29.7 ± 14.5%) in BD patients was significantly
higher (P < 0.05, Table 1) than in normal controls and
N-BD controls (17.7 ± 6.6% and 17.2 ± 1.1%,
respec-tively). The percentages of activated T-cells and
T-cyto-toxic/suppressor cells were similar in BD patients (26.1 ±
16.2% / 26.7 ± 20.7%), normal controls and N-BD
con-trols (23.8 ± 9.4% / 31.1 ± 5.8% and 29.2 ± 9.3% / 28.5 ±
4.0%, respectively).
Spontaneous and PHA-induced IFN-
γ
and TNF-
α
production were decreased
and IL-2 release was increased in BD patients
The spontaneous and PHA-induced production of IFN-
γ
,
TNF-
α
, IL-2 and IL-1
β
in N-BD controls were not
dif-ferent from those in normal controls (Table 2).
A significant decrease in spontaneous IFN-
γ
produc-tion was observed in BD patients (7.8 ± 1.5 pg/ml) as
compared with normal controls and N-BD controls (126.1
± 28.8 pg/ml and 108.0 ± 32.1 pg/ml; P < 0.005; Table 2).
PHA induced a significant increase in IFN-
γ
production in
normal controls and N-BD controls (623.5 ± 94.9 pg/ml
and 571.2 ± 101.1 pg/ml) compared with the level in BD
patients (22.9 ± 3.8 pg/ml; P < 0.005, Table 2).
Table 1 Percentages of T-cells, T-helper cells and B-cells in the BD patients and the two control groups
Group T-cells Activated T-cells B-cells T-helper cells T-cytotoxic/ suppressor cells Normal controls 63.1 ± 12.7 23.8 ± 9.4 17.7 ± 6.6 31.4 ± 5.7 31.1 ± 5.8 N-BD controls 68.6 ± 1.6 29.2 ± 9.3 17.2 ± 1.1 39.6 ± 1.8 28.5 ± 4.0 BD patients 46.9 ± 18.8* 26.1 ± 16.2 29.7 ± 14.5** 19.5 ± 5.5* 26.7 ± 20.7 * P < 0.02; BD patients vs normal controls and N-BD controls; ** P < 0.05, BD patients vs normal controls and N-BD controls Table 2 Spontaneous and
PHA-induced IFN-γ, TNF-α and IL-2 release in the BD pa-tients and the two control groups
* P < 0.005, BD patients vs normal controls and N-BD controls (spontaneous release); ** P < 0.005, BD patients vs normal controls and N-BD controls (PHA-induced)
Group IFN-γ TNF-α IL-2 IL-1 β
(pg/ml) (pg/ml) (pg/ml) (pg/ml) Normal controls Spontaneous 126.1 ± 28.8 107.1 ± 21.5 5.4 ± 1.1 124.1 ± 25.3 PHA-induced 623.5 ± 94.9 239.3 ± 110.0 17.3 ± 4.0 165.7 ± 30.8 N-BD controls Spontaneous 108.0 ± 32.1 90.2 ± 27.6 6.1 ± 1.1 109.1 ± 31.1 PHA-induced 571.2 ± 101.1 257.3 ± 129.0 19.2 ± 5.1 125.1 ± 36.7 BD patients Spontaneous 7.8 ± 1.5* 68.7 ± 16.1* 14.4 ± 6.9* 119.9 ± 36.7 PHA-induced 22.9 ± 3.8** 84.1 ± 19.3** 73.9 ± 34.5** 151.1 ± 20.3
A significant decrease in spontaneous TNF-
α
produc-tion was found in BD patients (68.7 ± 16.1 pg/ml) as
com-pared with normal controls and N-BD controls (107.1 ±
21.5 pg/ml and 90.2 ± 27.6 pg/ml; P < 0.005, Table 2). PHA
stimulation increased TNF-
α
production in normal
con-trols and N-BD concon-trols (239.3 ± 110.0 pg/ml and 257.3 ±
129.0 pg/ml), but not in BD patients (84.1 ± 19.3 pg/ml).
Thus, compared with controls, BD patients responded
poorly to PHA stimulation as far as TNF-
α
production was
concerned (P < 0.005).
A significant increase in spontaneous IL-2 production
was seen in BD patients (14.4 ± 6.9 pg/ml) compared with
normal controls and N-BD controls (5.4 ± 1.1 pg/ml and
6.1 ± 1.1 pg/ml; P < 0.005, Table 2). PHA stimulation
in-creased the production of IL-2 in BD patients (73.9 ±
34.5 pg/ml) compared with normal controls and N-BD
controls (17.3 ± 4.0 pg/ml and 19.2 ± 5.1 pg/ml; P < 0.005,
Table 2).
The spontaneous production of IL-1
β
in BD patients
was not different from that in normal controls and N-BD
controls. Upon stimulation with PHA, levels of IL-1
β
in BD patients remained similar to those in controls
(Table 2).
Spontaneous sCD4 and sCD8 production was increased
and PHA-induced sCD4, sCD8 and sIL-2R release
was decreased in BD patients
The spontaneous and PHA-induced production of sIL-2R,
sCD4 and sCD8 in N-BD controls was not different from
that in normal controls (Table 3).
Spontaneous release of sIL-2R was not significantly
dif-ferent among patients (3.2 ± 1.0 pmol/ml), normal controls
(4.3 ± 2.3 pmol/ml) and N-BD controls (3.8 ± 2.4 pmol/
ml). PHA stimulation increases sIL-2R release in normal
controls and N-BD controls (120.8 ± 17.6 pmol/ml and
109.0 ± 21.4 pmol/ml), but only a modest increase in BD
patients (8.1 ± 4.3 pmol/ml). PHA induced a statistically
significant increase in sIL-2R production in normal
con-trols and N-BD concon-trols, as compared with BD patients
(P < 0.005, Table 3).
A spontaneous increase in sCD4 production was
ob-served in BD patients (19.7 ± 2.3 U/ml) as compared with
normal controls and N-BD controls (4.5 ± 1.9 U/ml and
3.2 ± 2.1 U/ml; P < 0.005). PHA stimulation increased
sCD4 production in the normal controls and N-BD
con-trols (22.6 ± 3.4 U/ml and 24.1 ± 5.2 U/ml), but not in BD
patients (16.4 ± 4.3 U/ml; Table 3).
A spontaneous increase in sCD8 production was
ob-served in BD patients (265.2 ± 78.1 U/ml) as compared
with normal controls and N-BD controls (132.7 ± 46.1 U/
ml and 112.3 ± 52.1 U/ml; P < 0.005). PHA stimulation
increased sCD8 release in normal controls (597.3 ± 119.0 U/
ml), N-BD controls (539.4 ± 65.2 U/ml) and BD patients
(340.1 ± 92.8 U/ml). PHA-stimulated sCD8 release was
significantly lower in patients than in controls (P < 0.005;
Table 3).
Recombinant IL-2-induced [
3H]-thymidine incorporation
was lower in BD patients than in normal controls
As demonstrated in Fig. 1, the spontaneous incorporation
of [
3H]-thymidine into MNC of BD patients (626 ±
353 cpm) and normal controls (504 ± 170 cpm) was not
significantly different. However, after incubation with
re-combinant IL-2, [
3H]-thymidine uptake in BD patients
(1191 ± 385 cpm) was significantly lower than in normal
controls (2136 ± 355 cpm; P < 0.001).
PHA-induced IL-2R
α
and
β
chain expression on MNC
of BD patients was lower than on MNC of controls
The expression of IL-2R
α
chain (343.1 ± 29.4 MFI) and
β
chain (204.2 ± 40.7 MFI) on T-cells of patients was not
Table 3 Spontaneous and PHA-induced release of sIL-2R, sCD4 and sCD8 in the BD patients and the two control groupsGroup sIL-2R sCD4 sCD8
(pmol/l) (U/ml) (U/ml) Normal controls Spontaneous 4.3 ± 2.3 4.5 ± 1.9 132.7 ± 46.1 PHA-induced 120.8 ± 17.6 22.6 ± 3.4 597.3 ± 119.0 N-BD controls Spontaneous 3.8 ± 2.4 3.2 ± 2.1 112.3 ± 52.1 PHA-induced 109.0 ± 21.4 24.1 ± 5.2 539.4 ± 65.2 BD patients Spontaneous 3.2 ± 1.0 19.7 ± 2.3* 265.2 ± 78.1* PHA-induced 8.1 ± 4.3** 16.4 ± 4.3** 340.1 ± 92.8** * P < 0.005, BD patients vs normal controls and N-BD controls (spontaneous release);
** P < 0.005, BD patients vs normal controls and N-BD controls (PHA-induced)
Fig. 1 Recombinant IL-2 (rIL-2) induced a significantly lower [3H]-thymidine incorporation into MNC of Bowen’s disease
different from that on T-cells of normal controls (369.0 ±
80.6 and 225.1 ± 126.7 MFI, respectively). However,
PHA induced significantly lower IL-2R
α
chain (395.8 ±
30.5 MFI) and IL-2R
β
chain (211.9 ± 15.7 MFI)
expres-sion in BD patients than in normal controls (465.0 ± 37.5
and 321.1 ± 233.5 MFI; P < 0.005 and P < 0.001,
respec-tively; Table 4).
Discussion
In the present study, we investigated cytokine production
and immune responses in patients with BD and in healthy
controls. The cutaneous response to nonspecific DTH
antigen (DNCB) and the proportions of each lymphocyte
population were determined as indicators of the in vivo
immune status. Analysis of the results revealed depressed
cell-mediated immunity in BD patients in the form of
im-paired DTH responses to DNCB and a reduction in T-cells
and T-helper cell percentages, in comparison with
con-trols. However, the proportion of B-cells was elevated in
BD patients. This defective cell-mediated immunity in
BD patients was consistent with a decreased release of
IFN-
γ
which is produced by T-helper 1 cells. The plasma
sIL-2R level is a sensitive and quantitative marker of
cir-culating peripheral MNC activation [24] and also reflects
the status of lymphocyte activation [25]. Thus, the similar
percentage of activated T-cells among BD patients,
nor-mal controls and N-BD controls could, in part, explain the
similar plasma sIL-2R level and spontaneous IL-2R
re-lease among the three groups.
PHA stimulation induced significant increases in
sIL-2R, sCD4 and sCD8 in normal controls and N-BD
con-trols, but not in BD patients. This suggests that T-cells in
BD patients are relatively anergic in their response to
mi-togen stimulation compared with cells of the other two
control groups. IL-1
β
and TNF-
α
production were used
as indicators of monocyte/macrophage activation. sCD4
and sCD8 release were used as indicators of
helper/in-ducer and suppressor/cytotoxic T-cell activation,
respec-tively [13, 15–17]. IL-2 and IFN-
γ
production were taken
as reflecting Th1 cell function. In this study, neither
spontaneous nor PHA-induced IL-1
β
production differed
among patients, normal controls or N-BD controls, but
spontaneous and PHA-stimulated TNF-
α
production
were decreased in BD patients. Thus, we believe that
monocyte function may not be selectively defective in
BD.
In BD patients, there was an increase in the
sponta-neous release of IL-2 (Table 2), sCD4 and sCD8 (Table 3)
compared with the release in normal controls and N-BD
controls, indicating a pre-excitation state of T lymphocytes
in BD. In addition, PHA stimulated a marked increase in
2, but did not change the expression of membrane
IL-2R (
α
and
β
chains, Table 4) and produced a negligible
increase in sIL-2R production in BD patients compared
with controls. Furthermore, IL-2-stimulated [
3H]-thymi-dine incorporation into MNC was also significantly
de-creased in BD patients compared with normal controls
(Fig. 1). These findings suggest defective IL-2R
expres-sion and function in patients suffering from BD.
The soluble form of IL-2R is considered to be the
product of a proteolytic cleavage of the membrane
mole-cule. It can bind efficiently to IL-2 to maintain the
home-ostasis of the immune response [26]. Therefore,
discrepan-cies in the interrelationships among IL-2 production,
mem-brane IL-2R expression, and sIL-2R release upon PHA
stimulation may indicate the intrinsic defects in
lympho-cytes that may lead to the impairment of IL-2-mediated
function in these patients [27]. Defective lymphocyte
func-tion may also bring about a decline in spontaneous and
PHA-stimulated IFN-
γ
and TNF-
α
production (Table 1).
Decreased IL-2R expression in BD patients leads to
in-effective binding between IL-2 and IL-2R and depressed
[
3H]-thymidine incorporation by MNC. IL-2R includes at
least three distinct subunits, the
α
chain (55 kDa), the
β
chain (75 kDa) and the
γ
chain (64 kDa) [28]. Different
combinations of the three subunits form the three classes
of IL-2R. Low-affinity IL-2R consists of the
α
chain,
inter-mediate-affinity IL-2R includes the
β
and
γ
chains, and
high-affinity IL-2R contains all three chains. The IL-2R
α
chain can bind with IL-2 but has little to do with
intracel-lular signal transduction. The IL-2R
β
chain plays a
cru-cial role in intracellular signal transduction induced by
IL-2. The IL-2R
γ
chain also participates in the
mecha-nism of intracellular signal transduction once interaction
with IL-2 has taken place. By measuring IL-2R
α
and
β
chains, we could evaluate the binding affinity between IL-2
and IL-2R [29]. Our findings show that the expression of
IL-2R
α
and
β
chains in BD patients after PHA
stimula-tion was less than that in normal controls. PHA is a
macrophage-dependent T-cell activator, so the unchanged
expression of IL-2R
α
and
β
chains after PHA stimulation
indicates defective expression of IL-2R
α
and
β
chains by
T-cells in patients with BD. This defect causes the
defi-cient IL-2R function in patients with BD, which has not
Table 4 Spontaneous and PHA-induced expression of IL-2R αand βchains on T-cells in the BD patients and the normal control group (MFI mean fluorescence intensity)Group IL-2R αchain (MFI) IL-2R βchain (MFI)
Spontaneous PHA-induced Spontaneous PHA-induced
Normal controls 369.0 ± 80.6 465.0 ± 37.5* 225.1 ± 126.7 321.1 ± 233.5** BD patients 343.1 ± 29.4 395.8 ± 30.5 204.2 ± 40.7 211.9 ± 15.7 * P < 0.005, normal controls vs BD patients (PHA-induced); ** P < 0.001, normal controls vs BD patients (PHA-induced)
been reported previously. From these findings we suggest
that unsuccessful binding between IL-2 and IL-2R is
caused by an abnormal expression of IL-2R on T-cells and
brings about an immunological dysfunction in BD
pa-tients.
There are several possible explanations for the IL-2R
defect in BD patients. First, long-term exposure of MNC
to arsenic may impair IL-2R. Arsenic is known to exert a
biphasic effect on the proliferation response of
lympho-cytes, that is, their proliferation is amplified at low arsenic
concentrations and inhibited at high concentrations [30,
31]. Arsenic concentrations in urine, frequently used as an
index of exposure [32], have been found to be
signifi-cantly higher in BD patients from the endemic area than
in healthy controls [33, 34]. Consequently IL-2R
impair-ment in our BD patients may have been due to chronic
ar-senical poisoning in the endemic area. Second, certain
im-munosuppressive factors may be released in BD,
impair-ing the synthesis of IL-2R in activated lymphocytes.
Third, the cancer tissue may release certain
IL-2R-spe-cific binding factors or antagonists to block IL-2R on the
surface of activated lymphocytes. However, the molecular
mechanism of the IL-2R defect in BD remains to be studied.
Acknowledgements This study was supported by the National Science Council of the Republic of China (research grant NSC 84-2621-B-037-002-Z).References
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![Fig. 1 Recombinant IL-2 (rIL-2) induced a significantly lower [ 3 H]-thymidine incorporation into MNC of Bowen’s disease](https://thumb-ap.123doks.com/thumbv2/9libinfo/7477900.113183/4.892.454.821.130.339/recombinant-induced-significantly-lower-thymidine-incorporation-bowen-disease.webp)
