Thyroid autoantibodies in euthyroid non-pregnant women with recurrent spontaneous abortions

This study was undertaken to evaluate the incidence of thyroidautoantibodies in women with a history of recurrent (three ormore consecutive) spontaneous abortions. A total of 22 euthyroidnon-pregnant habitual aborters were analysed for thyreoglobulinand thyroid peroxidase antibodies; 22 nulligravidae and 22 multigravidaewithout endocrine dysfunction served as controls. Both thyroidantibodies were assayed using highly sensitive, commerciallyavailable enzyme-linked immunosorbent assay kits. Eight of the22 women with recurrent spontaneous abortions (36%) but onlytwo of the 22 nulligravidae controls (9%; ² test, P = 0.03)and one of 22 multigravidae subjects (5%; ² test, P < 0.01)demonstrated positive titres (> 100 IU/ml, as recommendedby the manufacturer) of thyreoglobulin, thyroid peroxidase orboth antibodies. The mean ± SD antibody concentrationswere 102.5 ± 226.5 in the study versus 20.9 ±68.8 in the nulligravidae (U-test, P = 0.057) and 26.4 ±60.2 IU/ml (P = 0.097) in the multigravidae population for thyroidperoxidase, and 47.7 ± 57.9 versus 24.1 ± 31.9(U-test, P = 0.051) and 28.1 ± 27.9 IU/ml (P = 0.059)for thyreoglobulin. In conclusion, the incidence of thyroidantibodies in euthyroid women with habitual abortions appearsto be significantly increased compared with the controls ofreproductive age without previous abortions. Although the importantissue of cause and effect has not been fully clarified, thisfinding suggests that thyroid antibodies may be a marker forautoimmune-mediated recurrent spontaneous abortions, not dissimilarto, for example, anticardiolipin.     

Variations of the Amnionless gene in recurrent spontaneous abortions

Recurrent spontaneous abortions (RSA) are estimated to affect 0.5-1% of couples trying to have a child. The causes of RSA are unknown in the majority of cases. This study aimed to determine whether homozygous mutations in the AMN gene in a fetus cause spontaneous abortions in humans, as they are known to cause spontaneous abortions in mice. The study was conducted by screening 40 couples and 5 women with three or more unexplained spontaneous abortions for heterozygous mutations in the AMN gene using denaturing high-performance liquid chromatography. Altogether, 3 exonic and 11 intronic sequence variations were found. There were no significant differences in the frequencies of the variations between the patients and a control group. One of the exonic variations was non-synonymous, and three of the variations may affect gene splicing. None of the putative phenotype-affecting variations were found in both partners in any couple. These results indicate that RSA in the couples studied cannot be explained by homozygous AMN mutations in the fetus. However, two couples had different, potentially deleterious variations in both partners. If these variations have a phenotypic effect, the RSA experienced by these couples may be caused by mutations in the AMN gene. In addition, birthplaces of the patients' ancestors revealed some clustering, suggesting that some patients may carry a founder mutation in another gene which may contribute to RSA.     

Increased frequency of complement C4 'null' alleles in recurrent spontaneous abortions.

Typings for major histocompatibility antigens HLA A, B, C and DR and for complement C4A, C4B and factor B were performed for 59 Finnish couples experiencing at least three consecutive recurrent spontaneous abortions (RSA). Forty-one of them were primary abortion (PA) couples with no children and 18 were secondary abortion (SA) couples who had one or two children before abortions. HLA sharing in A and B loci was slightly but significantly increased (15%, P less than 0.05) among RSA couples compared to the controls, as was DR sharing among SA couples compared to PA couples (50% versus 22%, P less than or equal to 0.05). The most interesting new finding, however, was the statistically significant increase of complement C4 functionally silent, i.e. C4 'null', alleles in RSA couples. C4 is a duplicated gene and its products differ in their functions in the complement cascade. C4A null alleles were equally increased in PA wives and in PA husbands (32%, P less than or equal to 0.05) compared to the controls (18%) and C4B null alleles in SA wives (56%, P less than or equal to 0.05) and in SA husbands (50%) compared to the controls (29%). Therefore, the offspring of RSA couples have a significantly increased risk of inheriting several null alleles. The majority, 95% (P less than 0.001) of PA couples and 83% of SA couples, had at least one C4A or C4B null in their phenotypes compared to 66% among Finnish controls.     

Effect of intravenous immunoglobulin treatment on the Th1/Th2 balance in women with recurrent spontaneous abortions

PROBLEM: The way by which intravenous immunoglobulin (IvIg) acts to prevent immunlogically mediated recurrent spontaneous abortions (RSA) has not been clarified. In the present study, a possible effect of IvIg on the T helper cell (Th1/Th2) balance was investigated in abortions of either alloimmune or autoimmune abnormalities. METHOD OF STUDY: The study included 21 women treated with IvIg before conception because of a history of RSA characterized by alloimmune abnormalities (n = 15) or associated with anti-phospholipid antibodies (APA) (n = 6). Peripheral blood samples, collected before and 5 days after the first IvIg infusion, were stimulated, and Th1 and Th2 cells were detected by flow-cytometric analysis using a combination of monoclonal antibodies against T-cell surface markers and intracellular interferon (IFN)-gamma and interleukin (IL)-4. The percentage of IFN-gamma-producing (Th1) and IL-4-producing (Th2) cells and the Th1/Th2 ratio were compared between pre- and post-infusion samples. RESULTS: A decrease of Th1 percentage in 66.6% of the cases and a concurrent Th2 percentage increase (47.61%) resulted in a decrease in the Th1/Th2 ratio in most of the cases (76.1%) (p < 0.01). Similar results were found in Group A (Th1/Th2 decreased in 60% of the cases, p < 0.05), while in Group B the effect of IvIg was not clear (Th1/Th2 increased in three and decreased in another three cases). CONCLUSION: Our finding suggests that IvIg administration in women with alloimmune RSA enhances Th2 polarization. This is not always the case with APA-associated abortions.     

Adverse influence of numbers of previous miscarriages on results of paternal lymphocyte immunization in patients with recurrent spontaneous abortions

PROBLEM: To determine whether an increase in the number of previous miscarriages in recurrent spontaneous abortion patients is a risk factor in subsequent pregnancies with paternal lymphocyte immunotherapy. METHOD OF STUDY: Live birth rates with reference to previous abortion numbers in recurrent spontaneous abortion patients were statistically compared between paternal lymphocyte immunotherapy and control groups, the latter retrospectively researched using historical data before 1981 in our clinic. RESULTS: The overall live birth rate was 73% (169/232) in the immunotherapy group, and 48% (47/97) in controls (P <0.05). According to previous abortion numbers, the rates were 77% (114/148) versus 55% (36/65) (P < 0.05) for three previous abortions, 70% (40/57) versus 38% (8/21) (P < 0.05) for four and 56% (15/27) versus 27% (3/11) (not significant) for five, in the study and control groups, respectively. CONCLUSIONS: The results confirm the efficacy of paternal lymphocyte immunotherapy, but demonstrate that the success rate deteriorates with the number of previous miscarriages.     

Circulating cytokines and CD30 in normal human pregnancy and recurrent spontaneous abortions

Concentrations of the T-helper (Th) 1 cytokines interleukin (IL)-2, tumour necrosis factor (TNF) -alpha, TNF-beta and interferon-gamma, Th2 cytokines IL-4, IL-5, IL-6, IL-10 as well as those of soluble CD30 in sera have been examined during the three trimesters of gestation, at delivery in normal pregnancy, and at the time of spontaneous abortion in women with a history of unexplained recurrent spontaneous abortion (RSA). Significantly higher concentrations of the Th2 cytokines IL-6 and IL-10 were found at normal delivery than in women with RSA, and conversely significantly increased concentrations of the Th1-type cytokine TNF-alpha were found in RSA as compared with successful pregnancy. In abortion-prone women who had a successful pregnancy, significantly higher concentrations of IL-6 and significantly lower concentrations of TNF-alpha were found as compared with abortion-prone women who had another abortion, supporting the notion that Th2- and Th1-bias are associated with successful and unsuccessful pregnancy respectively. Serum CD30 concentrations did not correlate with the outcome of pregnancy. These findings support observations drawn from experiments on the cytokine secretion profiles of peripheral blood mononuclear cells and decidual lymphocytes which suggest that normal pregnancy is Th2-biased and that unexplained RSA is associated with Th1-type reactivity.     

HLA-G polymorphisms in couples with recurrent spontaneous abortions

The etiology of a fraction of recurrent spontaneous abortions (RSA) may involve immunological mechanisms. Aberrant profiles of Th1 and Th2 cytokines have been observed which are not present in uncomplicated pregnancies. Studies of classical HLA class I and II antigens in relation to RSA have not been conclusive. Furthermore, these antigens are not expressed in the placenta with the exception of HLA-C. However, HLA-G is expressed on especially invasive cytotrophoblasts and exists in both membrane and soluble forms. HLA-G may be involved in materno-fetal tolerance. Therefore, 61 RSA couples (with three or more spontaneous abortions) and 47 fertile control couples were HLA-G genotyped by direct DNA sequencing and analyzed for specific polymorphisms. No statistically significant differences were observed in the distribution of HLA-G alleles between controls and RSA couples, however, 15% of the RSA women carried the HLA-G*0106 allele compared to 2% of the control women. The 14 bp deletion polymorphism in exon 8 was investigated separately. There were a greater number of heterozygotes for the 14 bp polymorphism in the group of fertile control women than expected, according to Hardy-Weinberg equilibrium. Furthermore, the HLA-G alleles without the 14 bp sequence were prominent in the RSA males in contrast to the RSA women in whom alleles including the 14 bp sequence were frequently observed, especially as homozygotes. These results are discussed in relation to two hypotheses concerning HLA-G and RSA. A hypothesis of HLA-G histo-incompatibility between fetus/placenta and the mother was not supported by the data. Another hypothesis concerned certain HLA-G alleles associated with an altered expression profile of HLA-G isoforms or reduced expression of certain HLA-G isoforms.     

Intravenous immunoglobulin treatment in women with recurrent abortions: increased cytokine levels and reduced Th1/Th2 lymphocyte ratio in peripheral blood

PROBLEM: The aim of this study was to investigate changes in peripheral blood Th1/Th2 cytokine levels and lymphocyte ratios after massive intravenous immunoglobulin (MIVIg) treatment for women with recurrent spontaneous abortion (RSA) of unexplained etiology. METHOD OF STUDY: Serum Th1 (IFN-gamma, TNF-alpha) and Th2 cytokine (IL-4, IL-10) levels were assessed by ELISA methods (n = 9) and peripheral blood Th1/Th2 lymphocyte ratios (n = 4) by flow cytometry before and after MIVIg treatments in women with four or more consecutive RSA. RESULTS: Pre-treatment serum IFN-gamma (0.06 +/- 0.09 pg/mL, mean +/- SD), TNF-alpha (0.21 +/- 0.45 pg/mL), IL-4 (0.70 +/- 1.16 pg/mL), and IL-10 (1.12 +/- 1.67 pg/mL) increased to 0.17 +/- 0.16 pg/mL, 0.77 +/- 0.28 pg/mL, 1.82 +/- 0.89 pg/mL, and 3.44 +/- 0.48 pg/mL, respectively, after MIVIg treatments (P < 0.05). CD4-positive IFN-gamma/IL-4 lymphocyte ratios (17.3 +/- 9.1) were reduced to 11.5 +/- 7.1 after treatment (P < 0.05). CONCLUSIONS: Massive intravenous immunoglobulin treatments increased peripheral blood cytokine levels and decreased Th1/Th2 lymphocyte ratios; thus, MIVIg treatments modify the peripheral Th1/Th2 balance.     

Cytokine production by maternal lymphocytes during normal human pregnancy and in unexplained recurrent spontaneous abortion

It has been proposed that successful pregnancy is a T helper 2-type phenomenon, and that T helper (Th)1-type reactivity is deleterious to pregnancy. The objective of this study was to compare the concentrations of Th1 and Th2 cytokines produced by peripheral blood mononuclear cells from women undergoing unexplained recurrent spontaneous abortion (RSA) with those produced during normal pregnancy at a similar gestational stage. The control group consisted of 24 women with a history of successful pregnancies and the abortion group comprised of 23 women with a history of unexplained RSA. Blood from the control group was obtained at the end of the first trimester as gestational age controls for the abortion group from whom blood was collected at the time of abortion. Phytohaemagglutinin-stimulated peripheral blood cell culture supernatants were analysed for concentrations of cytokines. Significantly higher concentrations of Th2 cytokines were produced by the first trimester normal group than by the RSA group, while significantly higher concentrations of Th1 cytokines were produced by the abortion group as compared to first trimester normal pregnancy, indicating a distinct Th2-bias in normal pregnancy and a Th1-bias in unexplained RSA.     

Th1 and Th2 cytokine profiles in recurrent aborters with successful pregnancy and with subsequent abortions

BACKGROUND: This study compared Th1-Th2 cytokine profiles in a subgroup of recurrent aborters who had an abortion with those in a subgroup of recurrent aborters who had a successful pregnancy. METHODS: Fifty-four women with a history of at least three normal pregnancies, 24 women with a history of recurrent spontaneous abortion (RSA) followed by abortion (RSA-->A) and 39 women with a history of RSA followed by normal pregnancy (RSA-->N) were studied. Blood samples and placentas were obtained at the time of delivery or abortion; peripheral blood mononuclear cells were stimulated separately with phytohaemagglutinin and with autologous placental cells, and the secreted cytokines estimated. RESULTS: Peripheral blood mononuclear cells from the RSA-->N subgroup secreted higher concentrations of Th1-type cytokines as compared with normal pregnant women, indicating a higher Th1 bias in these women. However, women in the RSA-->N subgroup had significantly higher concentrations of Th2 cytokines as compared with women in the RSA-->A subgroup. A comparison of Th1:Th2 cytokine ratios indicated a higher Th2 bias in RSA-->N women as compared with RSA-->A women. CONCLUSIONS: We conclude that abortion-prone women who proceed to have successful pregnancy are more Th2-biased than abortion-prone women who abort, and that recurrent aborters who undergo spontaneous abortion have a stronger Th1 bias than aborters who have normal pregnancy.     

Circulating interferon-gamma- and interleukin-4-secreting cells in recurrent spontaneous abortions.

PROBLEM: Are recurrent spontaneous abortions (RSAs) associated with deviation of circulating cytokine-secreting cells? METHOD OF STUDY: Interferon (IFN)-γ- and interleukin (IL)-4-secreting cells were identified by enzyme-linked immunospot (ELISPOT) in blood from 34 women with RSA. Samples were taken before pregnancy and/or pregnancy weeks 7–10, 17–20, and after terminated pregnancy. Eleven healthy primigravidae and 10 nonpregnant women served as controls. RESULTS: No significant difference in numbers of IFN-γ- and IL-4-secreting cells was noted within the RSA group when abortions and successful pregnancies were compared in samples taken before pregnancy. The number of IFN-γ- as well as IL-4-secreting cells in pregnancy weeks 17–20 in the RSA group was significantly higher compared with before pregnancy, pregnancy weeks 7–10, and after pregnancy. In samples from non-pregnant women, the number of IFN-γ- and IL-4-secreting cells was significantly higher in the RSA group compared with controls. CONCLUSIONS: Our results do not indicate a systemic shift in the general balance between T helper 1- and T helper 2-type cytokine pattern. A local shift at the fetomaternal interface seems more probable.     

Immunotherapy for recurrent spontaneous abortions in a Chinese population

The efficacy of immunotherapy for the treatment of recurrent spontaneous abortions was tested in patients selected from the same ethnically homogeneous population of Chinese in Taiwan in whom the immunogenetics of gestational trophoblastic tumors and of recurrent spontaneous abortion had been studied. The patients, who included both primary and secondary aborters, were randomly assigned to three groups: those who were immunized with their own lymphocytes (controls) (49); those who were immunized with their husbands' lymphocytes (39); and those who were immunized with third party lymphocytes (11). The data were analyzed individually for the primary and secondary aborters and collectively for both groups combined. The number of babies born, the number of current pregnancies, and the number of recurrent abortions were not statistically significantly different between the control and the immunized groups, and a similar small number of congenital abnormalities (4-9%) occurred in both the control and immunized groups. The increase in the blocking effect for the mixed lymphocyte reaction was not related to the success of the postimmunization pregnancies. Thus, this study does not show any significant improvement in the rate of livebirths in women immunized with their husbands' lymphocytes or with third party lymphocytes compared to that in a placebo-controlled group of women.     

MTHFR基因C677T位点多态性与不明原因重复性自然流产的相关性

目的　检测不明原因重复性流产 (unexplained recurrent spontaneous abortion,URSA)患者亚甲基四氢叶酸还原酶 (methylenetetrahydrofolate reductase,MTH FR)基因 C6 77T位点多态性 ,探讨其与血清同型半胱氨酸、叶酸、维生素 B1 2 及与不同临床特征的关系。　方法　 U RSA非孕期患者 5 7例 ,对照组 5 0名 ,空腹血清总高半胱氨酸 (homocysteine,Hcy)的检测采用高压液相色谱法 ,血清叶酸、维生素 B1 2 的检测采用放射免疫法。MTH FR基因 C6 77T多态性采用聚合酶链反应 -限制性片段长度多态性技术检测。结果　 URSA患者组 C/ C基因型频率显著低于正常对照组者 ,总的突变 T等位基因频率显著高于对照组。MTHFR T/ T基因型患者血清 Hcy水平显著增高 ,血清叶酸水平显著降低 ,MTHFR C6 77T基因型在不同年龄、地区、流产时间、流产性质患者的分布差异无显著性。流产 3次以上 (包括 3次 )的患者 6 77T/ T基因型、携带 T等位基因的 C/ T T/ T基因型频率均大于流产次数少于 3次的患者。　结论　 MTH FRC6 77T基因多态性是 URSA发病的遗传风险因素。     

一氧化氮合酶3基因多态性与复发性早期自然流产的关系

目的探讨一氧化氮合酶3(nitric oxide synthase 3,NOS3)基因第4内含子27bp数目可变串联重复序列(variable number of tandem repeat,VNTR)多态性和第7外显子894(G/T)多态性与复发性早期自然流产(recurrent early spontaneous abortion,RESA)的相关性。方法选取140例RESA患者和140名健康妇女,应用聚合酶链反应-琼脂糖凝胶电泳法检测NOS3基因第4内含子VNTR多态性,聚合酶链反应-限制性片段长度多态性分析技术检测第7外显子894(G/T)多态性。结果RESA组aa ba基因型频率和a等位基因频率与正常对照组相比差异有统计学意义(χ2=4.51,P<0.05;χ2=4.29,P<0.05)。与bb基因型相比,携带a等位基因的妇女与RESA显著相关(OR为1.8,95%CI:1.04~3.24)。RESA组TT GT基因型频率和T等位基因频率与正常对照组相比差异无统计学意义(χ2=1.16,P>0.05;χ2=1.12,P>0.05)。与GG基因型相比,携带T等位基因的妇女与RESA无相关。结论NOS3基因第4内含子27bp数目可变的串联重复序列多态性与复发性自然流产密切相关,NOS3基因第7外显子894G/T多态性与RESA无明显相关性,a等位基因是RESA重要的遗传易感基因。     

Association of the maternal 14-bp insertion polymorphism in the HLA-G gene in women with recurrent spontaneous abortions

Human leukocyte antigen (HLA)-G has been postulated as an important immunotolerant molecule in maintaining fetal-maternal relationship. Recent reports indicated that the 14-bp deletion/insertion polymorphism in exon 8 of HLA-G gene influences HLA-G mRNA stability and isoform splicing patterns, thus modulating the levels of HLA-G expression. This might play an immunomodulatory role of HLA-G during implantation and pregnancy. In the present study, 109 unrelated fertile control women and 79 women who had experienced recurrent spontaneous abortion (RSA) were genotyped for the 14-bp insertion/deletion polymorphism. No significant difference was observed in the distribution of 14-bp insertion/deletion genotype between controls and the RSA group. However, a greater number of 14-bp insertion alleles exist in the RSA group than in the controls.     

TCRgammadelta + T lymphocytes in unexplained recurrent spontaneous abortions

PROBLEM: It is generally accepted that the immune system and cellular immunity in particular are involved in the mechanisms affecting the outcome of gestation. In order to evaluate a putative role of lymphocytes in the immunological mechanisms of unexplained recurrent spontaneous abortions (URSA), we studied peripheral blood lymphocyte subpopulations in 244 women with URSA and 44 controls. METHOD OF STUDY: Direct immunofluorescence in whole blood with the appropriate combinations of monoclonal antibodies and flow cytometry was used. RESULTS: The study showed: a) a statistically significant increase of the mean CD4/CD8 ratio (2.12+/-0.84 vs 1.85+/-0.63, P = 0,039); b) a statistically significant decrease of the mean value of the percentage of CD5+ CD19+ lymphocytes (0.4+/-0.6 vs 1.4+/-0.78, P < 0.0001); and c) a statistically significant increase of the percentage of T lymphocytes expressing TCRgammadelta (4.68+/-3.19 vs 2.61+/-1.14, P < 0.0001). It should be noted that a statistically significant high number of women with URSA (72/195, 36.9%) showed an increased percentage of TCRgammadelta T cells (> or = 5%, where 5 equals the mean value + 2 standard deviations (SD) of the mean value of controls), whereas such a high percentage was not found in any control subject. CONCLUSIONS: It seems that women who experienced URSA comprise a heterogeneous population, as far as immunological parameters are concerned. At least in a subgroup of them, TCRgammadelta + T cells could be considered to play a role in the immune pathogenesis of fetal loss.     

TH1/TH2细胞因子与习惯性流产的关系研究

目的通过测定习惯性流产患者（RSA）及正常妊娠妇女外周血血清TH1/TH2细胞因子的含量,探讨TH1/TH2细胞因子与习惯性流产发生的关系。方法采用酶联免疫吸附法检测30例RSA患者,72例正常妊娠妇女血清IL-2、IL-4、IL-10、IFN-γ、TNF-α及TNF-β水平并比较两组之间的差异。结果RSA患者IL-2、IL-4、IL-10、IFN-γ、TNF-α血清水平显著高于正常妊娠妇女（P〈0.05）,TNF-β血清水平显著低于正常妊娠妇女（P〈0.05）。结论血清IL-2、IL-4、IL-10、IFN-γ、TNF-α水平可能在习惯性流产发生中起重要作用。     

High anti-paternal cytotoxic T-lymphocyte precursor frequencies in women with unexplained recurrent spontaneous abortions

A number of cases of unexplained (idiopathic) recurrent spontaneous abortions may be attributable to immunological mechanisms. Several lines of evidence indicate that some immunocompetent effector cell populations play an important role in the pathogenesis of unexplained miscarriages. However a suitable method is lacking for defining an existing immunological background of recurrent spontaneous abortions. We tried to find a useful cellular immunological method, that is suitable for predicting the eventual immunological cause in the case of unexplained recurrent spontaneous abortions. We have examined the anti-paternal cytotoxic T-lymphocyte precursor frequencies by cell-mediated lympholysis and limiting dilution analysis in the peripheral blood of women with recurrent spontaneous abortions in order to reveal the functional role of this cell population in spontaneous abortions. An extremely high partner allo-antigen-specific cytotoxic T-lymphocyte precursor frequency was determined in the case of all those habitual aborters, where no other than an immunological cause could be responsible for the abortions. This phenomenon supports the important role of the T-lymphocytes in this disorder. We suggest that the immunological background of recurrent spontaneous miscarriages might be determined on the basis of a very high cytotoxic T-lymphocyte precursor frequency. This diagnostic test might be useful in selecting patients for immunotherapy.     

Status of peripheral blood natural killer cells in women with recurrent spontaneous abortions and infertility of unknown aetiology

The aim of this study was to investigate the functional status and immunophenotypic characteristics of natural killer (NK) cells in women who suffer recurrent spontaneous abortions (RSA) or have infertility of unknown aetiology. Peripheral blood mononuclear cells (PBMC) were obtained from 40 study patients and 13 normal healthy multiparous controls. NK cells were identified using anti-CD56 and anti-CD16 monoclonal antibodies (mAb). The expression of CD69, CD25, CD122, CD30, CD154, CD128 and CD94 on NK cells was detected using specific mAb and analysed by flow cytometry. CD69 expression on NK cells after ED(27) human trophoblast cell line co-culture with PBMC was also investigated. A significant increase in CD69 expression on CD56(+) NK cells was demonstrated in women with RSA (P < 0.005) and infertility (P < 0.05) as compared with that of normal controls. Conversely, CD94 expression was significantly decreased in women with RSA (P < 0.005) and infertility (P < 0.05) in comparison with that of controls. Increased CD69 expression on NK cells was induced after 24 h co-culture with ED(27). In conclusion, peripheral blood NK cells of women with RSA and infertility of unknown aetiology have higher proportions of activated NK cells in vivo. Unbalanced CD69 and CD94 expression may explain the underlying pathology.