Analysis of gammac-dependent cytokines-mediated immunoregulation

In the study of interleukin-2 (IL-2) -induced signal transduction system, we identified and cloned the third component of IL-2 receptor, IL-2Rgamma chain. Functional high affinity IL-2 receptor consists of three subunits, alpha, beta and gamma chains. Interestingly not only IL-2 but also IL-4, IL-7, IL-9, IL-15 and IL-21 utilize the gamma chain as an essential component of each receptors. Therefore the gamma chain is now called as a common gamma chain (gammac). Moreover the gene of gammac is on the X chromosome, and mutations of gammac gene cause human X-linked severe combined immunodeficiency (X-SCID) characterized by a complete or profound defect of T cells and NK cells, and by the presence of dysfunctional B cells. The dysfunctions in IL-7- and IL-15-induced signal transduction cause the T cell and NK cell defect, respectively and dysfunctions in both IL-4- and IL-21-induced signal transduction cause the B cell dysfunction in X-SCID patients. Gene therapy is a good candidate for X-SCID treatment because only the HLA-matched bone marrow transplantation is an effective therapy. Unfortunately because of an unexpected adverse effect, such gene therapy using retrovirus vector is now aborted. IL-21 is a recently identified cytokine, which shares the gammac. IL-21 regulates the proliferation of T cells, the proliferation and differentiation of B cells, and the activation and expansion of NK cells. We demonstrated that human IL-21 was produced from activated CD4+ central and effector memory T cells but not from naive CD4+ T cells nor CD8+ T cells. Furthermore we found that IL-21 supported cytokine-driven proliferation of CD4+ helper T cells cooperatively with IL-7 and IL-15.     

Transplantation of X-linked severe combined immunodeficient dogs with CD34+ bone marrow cells.

X-linked severe combined immunodeficiency (X-SCID) is the most common form of human SCID and is caused by mutations in the common gamma chain (gammac), a shared component of the interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21 receptors. BMT for human X-SCID results in engraftment of donor T-cells and reconstitution of normal T-cell function but engraftment of few, if any, donor B-cells and poor reconstitution of humoral immune function. Canine X-SCID is also caused by mutations in the yc and has an immunological phenotype identical to that of human X-SCID. We have previously reported that transplantation of nonconditioned X-SCID dogs with unfractionated histocompatible bone marrow results in engraftment of both donor B- and T-cells and reconstitution of normal T-cell and humoral immune function. In this study, we assessed the ability of purified canine CD34+ bone marrow cells to reconstitute lymphoid populations after histocompatible BMT in 6 nonablated X-SCID dogs. All dogs showed engraftment of donor T-cells, with T-cell regeneration occurring through a thymic-dependent pathway, and had reconstituted normal T-cell function. In contrast to our previous studies, only 3 dogs had engraftment of donor B-cells and reconstituted normal antigen-specific B-cell function post-BMT. The variable donor B-cell engraftment and reconstitution of normal humoral immune function observed in this study are similar to the outcomes observed in the majority of human X-SCID patients following BMT. This study demonstrates that canine CD34+ cells contain progenitors capable of immune reconstitution and is the first study to document the ability of CD34+ bone marrow cells to reconstitute normal B- and T-cell function in a nonablated large-animal model of BMT. This study also demonstrates that the quality of immune reconstitution following CD34+ BMT may be dosage dependent Thus canine X-SCID provides a large-animal preclinical model that can be used not only to determine the optimal conditions for both donor B- and T-cell engraftment following CD34 BMT, but also to develop and evaluate strategies for gene therapy protocols that target CD34 cells.     

X-SCID B cell responses to interleukin-4 and interleukin-13 are mediated by a receptor complex that includes the interleukin-4 receptor α chain (p140) but not the γ chain

This study investigates the effect of interleukin (IL)-4 mutant proteins and a monoclonal antibody to the IL-4 receptor α chain on IL-4 and IL-13 response by B cells from X-linked severe combined immunodeficiency (X-SCID) patients in which the common γ chain (γc chain) gene mutations have been fully characterized and no γc chain expression was detected. In this γc chain gene knockout model, it was confirmed that the γc chain is essential for B cell responses to IL-2 but not for IL-4 or IL-13. Dose-response curves for X-SCID and normal B cell responses to IL-4 were indistinguishable, showing that the loss of the γc chain did not diminish the sensitivity of B cells to IL-4. The mutant protein IL-4_Y124D and an antibody to the IL-4R α chain both inhibited responses of X-SCID B cells to IL-4 and IL-13, showing that X-SCID B cell responses to these cytokines are mediated by a receptor complex that includes the IL-4R α chain but not the γc chain. Another mutant protein, IL-4_R88D, which has greatly reduced affinity for IL-4Rα, was found to inhibit responses by normal B cells to IL-4 but not to IL-13. IL-4_R88D did not, however, inhibit X-SCID B cell responses to IL-4. This result is consistent with IL-4_R88D inhibition of responses mediated by receptor complexes that include the γc chain. We propose that X-SCID B cells responses to IL-4 are mediated by an IL-13 receptor complex comprised of the IL-4R α chain associated with the recently cloned IL-13R binding protein. This model has major implications for understanding normal B cell responses to IL-4.     

A novel mutant γc chain from a patient with typical phenotype of X-linked severe combined immunodeficiency (SCID) has partial signalling function for mediating IL-2 and IL-4 receptor action

Mutations of the common γ (γc) chain result in X-linked SCID (X-SCID), which is characterized by the reduction in number or absence of peripheral blood T cells and natural killer (NK) cells, with retention of normal numbers of B cells. In the present study we describe a novel mutant γc chain of an X-SCID patient with a typical X-SCID phenotype. This mutant receptor subunit is able to associate with Jak3 to transduce a weak signal. The Jak3-specific action is demonstrated by the induction of gene expression through the haematopoietin receptor response element (HRRE) by IL-2 and IL-4 in the experimental model of transiently transfected hepatoma cells over-expressing Jak3. This result suggests that a threshold in the γc–Jak3 interaction determines the X-SCID phenotype.     

Gene therapy of X-linked severe combined immunologic deficiency (SCID-X1)

X-linked severe combined immunodeficiency (SCID-X1) is a recessive hereditary disorder in which early T and Natural Killer (NK) lymphocyte development is blocked. The genetic disorder results from mutations in the common gamma c chain that participates in several cytokine receptors including the interleukin-2 (Il-2), Il-4, Il-7, Il-9, Il-15 receptors. SCID-X1 offers a reliable model for gene therapy as it is a lethal condition that is, in many cases, curable by allogeneic bone marrow transplantation. We have shown that retrovirus-mediated transfer of the gamma c cDNA induced gamma c chain expression and restored the function of the high-affinity IL-2 receptor on SCI-X1 EBV-transformed B-cell lines. We have the designed culture conditions to study NK-cell and T-cell development of CD34+ hematopoietic progenitor cells. In the culture systems, gamma c transduced CD34+ marrow cells from two SCID-X1 patients were able to mature into CD56+ and/or CD16+ NK cells and into CD4+ TCR alpha beta+ T cells. These preclinical results set the basis for a clinical study of ex-vivo gamma c gene transfer into CD34+ cells from SCID-X1 patients.     

Abnormal development of thymic dendritic and epithelial cells in human X-linked severe combined immunodeficiency

The X-linked form of severe combined immunodeficiency (X-SCID) is caused by mutations in the common cytokine receptor gamma chain and results in lack of T and NK cells and defective B cells. Without immune reconstitution, X-SCID patients typically die from infection during infancy. This report describes thymic epithelial (TE), lymphocyte, and dendritic cell (DC) differentiation in the thymic microenvironment of seven X-SCID patients who died before or after treatment for their immunodeficiency. X-SCID thymus consisted predominately of TE cells without grossly evident corticomedullary distinction. CD3+ and CD1a+ developing T cells and CD83+ thymic DC were reduced >50-fold when compared to age- and gender-matched control thymus (P < 0.001). TE expression of epithelial differentiation markers CK14, involucrin, and high molecular weight cytokeratins also differed in X-SCID versus normal thymus. These histopathologic findings indicate that in addition to T cells, thymic DC development and differentiation of TE cells are also abnormal in X-SCID.     

Janus kinase 3 (Jak3) is essential for common cytokine receptor gamma chain (gamma(c))-dependent signaling: comparative analysis of gamma(c), Jak3, and gamma(c) and Jak3 double-deficient mice

The common cytokine receptor gamma chain (gamma(c)) is an essential receptor component for IL-2, IL-4, IL-7, IL-9 and IL-15, and thereby gamma(c)-deficient mice exhibit impaired T cell and B cell development. The Janus family tyrosine kinase 3 (Jak3) is known to be associated with gamma(c), and the reported phenotypes of gamma(c)-deficient (gamma(c)(-)) and Jak3-deficient (Jak3(-)) mice are similar, indicating that Jak3 is an essential transducer of gamma(c)-dependent signals. Nevertheless, certain differences have been suggested related to the range of actions of gamma(c) and Jak3. To clarify whether gamma(c)-dependent cytokines can partially transduce their signals without Jak3, we compared lymphocyte development in gamma(c)(-), Jak3(-), and gamma(c) and Jak3 double-deficient (gamma(c)(-)Jak3(-)) mice in the same genetic background. With the exception that T and B cells in Jak3(-) mice express high levels of gamma(c), the defects in thymocyte and peripheral T cell and B cell development are indistinguishable among gamma(c)(-), Jak3(-) and gamma(c)(-)Jak3(-) mice. Interestingly, although Bcl-2 induction was previously suggested to be Jak3-independent, IL-7 cannot induce Bcl-2 expression in CD4 single-positive (SP) thymocytes in either gamma(c)(-) or Jak3(-) mice nor can IL-7 rescue CD4 SP thymocytes from dexamethasone-induced cell death in gamma(c)(-) or Jak3(-) mice. These results indicate that Jak3 is absolutely essential for gamma(c)-dependent T cell and B cell development, and for gamma(c)-dependent prevention of thymocyte apoptosis.     

Molecular and genetic basis of X-linked immunodeficiency disorders

Summary Within a short time interval the specific gene defects causing three X-linked human immunodeficiencies, agammaglobulinemia (XLA), hyper-IgM syndrome (HIGM), and severe combined immunodeficiency (XSCID), have been identified. These represent the first human disease phenotypes associated with each of three gene families already recognized to be important in lymphocyte development and signaling: XLA is caused by mutations of a B cell-specific intracellular tyrosine kinase; HIGM, by mutations in the TNF-related CD40 ligand, through which T cells deliver helper signals by direct contact with B cell CD40; and XSCID, by mutations in the chain of the lymphocyte receptor for IL-2. Each patient mutation analyzed to date has been unique, representing both a challenge for genetic diagnosis and management and an important resource for dissecting molecular domains and understanding the physiologic function of the gene products.Formerly at Department of Pediatrics, University of Pennsylvania School of Medicine and Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.     

Interleukin 2 receptor gamma chain (gamma(c)) knockout mice show less regularity in estrous cycle but achieve normal pregnancy without fetal compromise

PROBLEM: Implication of cytokines in pregnancy suggested but remains to be established. We studied the effect of cytokines on reproductive functions such as ovulation and pregnancy, with mutant mice lacking interleukin 2 receptor gamma (IL-2Rgamma), the so-called common gamma chain (gamma(c)), which is shared among receptors for multiple cytokines such as IL-2, IL-4, IL-7, IL-9 and IL-15. METHOD OF STUDY: Regularities of estrous cycles were observed by vaginal smear. Ovaries stimulated with postmenopausal serum gonadotropin (PMSG) were examined for the ovarian capacities. The uteri at 13 days of gestation were used for histological analysis of the maternal-fetal interface. RESULTS: The estrous cycles in gamma(c) knockout (gamma(c) KO) mice were irregular compared with wild-type mice, although, the mutants could become pregnant. No uterine natural killer (uNK) cell was found in the uterus at 13 days of pregnancy, and poor decidual formation and thickness of blood vessel walls were observed. Apparent differences were not seen in the numbers and weight of the fetuses between wild type and mutant animals, and fetuses were not compromised throughout pregnancy. CONCLUSIONS: The gamma(c) KO mice showed irregular estrous cycle but they could carry out normal pregnancy despite lacking uNK and cytokines actions of IL-2, 4, 7, 9 and 15.     

T<Superscript>+</Superscript> NK<Superscript>+</Superscript> IL-2 Receptor γ Chain Mutation: a Challenging Diagnosis of Atypical Severe Combined Immunodeficiency

Purpose

All reported patients with hypomorphic X-linked severe combined immunodeficiency (X-SCID) due to c.664C>T (p.R222C) mutations in the gene (IL2RG) encoding the common γ chain (γc) have presented with opportunistic infections within the first year of life, despite the presence of nearly normal NK and T cell numbers. Reporting five children of one extended family with hemizygous mutations in IL2RG, we explore potential diagnostic clues and extend our comprehension of the functional impact of this mutation.

Methods

Whole exome sequencing (WES); detailed immune phenotyping; cytokine-induced STAT phosphorylation; B, T, and NK cell activation; and quantification of sjTRECs in five Arab children with c.664C>T (p.R222C) IL2RG mutation.

Results

The mean age at clinical presentation with respiratory tract infection or diarrhea was 6.8 (range: 2–12) months. None of the children presented with opportunistic infections. Diagnostic clues were early onset in the first year of life, and a suggestive family history associated with reduced naïve CD4 T cells and absent switched memory B cells. Number and phenotype of NK cells and innate-like lymphocytes were normal. The diagnosis was made by WES and corroborated by absent STAT phosphorylation and reduced functional response after IL-2 and IL-21 stimulation. Four patients underwent successful hematopoietic stem cell transplantation.

Conclusions

As early diagnosis and treatment are important, a high index of suspicion in the diagnosis of c.664C>T (p.R222C) X-SCID is needed. This requires prompt genetic testing by next generation sequencing in order to avoid unnecessary delays in the definite diagnosis since immunological work up may not be discriminating. Assays directly testing cytokine signaling or cytokine-dependent functions are helpful in confirming the functional impact of the identified hypomorphic variants.

     

gamma(c) cytokines provide multiple homeostatic signals to naive CD4(+) T cells

Cytokines signaling through receptors sharing the common gamma chain (gamma(c)), including IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21, are critical for the generation and peripheral homeostasis of B, T and NK cells. To identify unique or redundant roles for gamma(c) cytokines in naive CD4(+) T cells, we compared monoclonal populations of CD4(+) T cells from TCR-Tg mice that were gamma(c) (+), gamma(c) (-), CD127(-/-) or CD122(-/-). We found that gamma(c) (-) naive CD4(+) T cells failed to accumulate in the peripheral lymphoid organs and the few remaining cells were characterized by small size, decreased expression of MHC class I and enhanced apoptosis. By over-expressing human Bcl-2, peripheral naive CD4(+) T cells that lack gamma(c) could be rescued. Bcl-2(+) gamma(c) (-) CD4(+) T cells demonstrated enhanced survival characteristics in vivo and in vitro, and could proliferate normally in vitro in response to antigen. Nevertheless, Bcl-2(+) gamma(c) (-) CD4(+) T cells remained small in size, and this phenotype was not corrected by enforced expression of an activated protein kinase B. We conclude that gamma(c) cytokines (primarily but not exclusively IL-7) provide Bcl-2-dependent as well as Bcl-2-independent signals to maintain the phenotype and homeostasis of the peripheral naive CD4(+) T cell pool.     

鸟氨酸氨甲酰基转移酶缺陷症三例临床和基因突变分析

目的 分析鸟氨酸氨甲酰基转移酶缺陷症(ornithine carbamoyltransferase deficiency,OTCD)的临床表现、遗传学特点,从基因水平了解OTCD的致病因素,达到基因诊断和遗传咨询的目的.方法 应用聚合酶链反应扩增3例OTCD患者的鸟氨酸氨甲酰转移酶(ornithine carbamoyltransferase,OTC)基因各个外显子所在片段,并进行直接测序,以检测突变.结果 例1在生后6月以呕吐起病,为错义突变T262I,其母亲表型正常,为T262I杂合突变;例2在2岁时以烦躁不安起病,为错义突变R277W,例2父母未行基因检测;例3以嗜睡在新生儿期起病,为错义突变I172M,其母表型正常,为I172M杂合突变.结论 基因分析是诊断OTCD有效可行的方法.T262I突变及R277W突变是症状较轻的温和突变,I172M突变是起病年龄早及症状重的突变.对致病基因进行突变检测不仅可以诊断OTCD,而且可以发现无症状的基因携带者,为遗传咨询及产前诊断提供依据.

Abstract：

Objective To analyze the clinical and genetic characteristics of three children with ornithine carbamoyltransferase deficiency(OTCD), and to provide a practical method for gene diagnosis and genetic counseling of the disease. Methods All exons of the ornithine carbamoyltransferase (OTC) gene were screened by polymerase chain reaction-DNA direct sequencing in the three OTCD patients. Results One patient firstly presented as vomiting at 6 month of age. A missense mutation of T262I was detected. His mother had the same mutation without any clinical symptoms. The second patient presented as restlessness, and had a missense mutation of R277W. Gene analysis of his parents was not available. The third patient presented as neonatal lethargy, harbored a missense mutation of I172M. His mother had the same mutation without any clinical symptoms. Conclusion Gene mutation analysis is a feasible way for diagnosing OTCD. Patients with I172M mutation present symptom early, while those with T262I and R277W mutations manifest symptoms later. Gene mutation analysis will be important for asymptomatic and prenatal diagnosis and genetic counseling.     

Human lung myofibroblasts as effectors of the inflammatory process: the common receptor gamma chain is induced by Th2 cytokines,and CD40 ligand is induced by lipopolysaccharide,thrombin and TNF-alpha

The common gamma (gamma c) chain, shared by Th1 and Th2 cytokines, is fundamental for the activation of hematopoietic cells, but its role in non-hematopoietic tissues has not been explored. Here we show that in normal lung fibroblasts IL-4 and IL-13 induce the expression of the gamma c chain and its association with Janus kinase (JAK) 3, while lung myofibroblasts constitutively express a gamma c chain displaying a limited association with JAK3. In the latter cells, without exogenous cytokines, gamma c/JAK3 controls, through autocrine loops, tyrosine kinase (TYK) 2 phosphorylation and the balance between functional (IL-4Ralpha, IL-13Ralpha 1) and decoy (IL-13Ralpha 2) high-affinity receptors. Moreover, JAK3 is also associated with a pre-phosphorylated IL-4Ralpha and CD40. This novel "heterotrimer" (p-IL-4Ralpha, CD40/JAK3) is functional and controls STAT3 phosphorylation and CD40 expression, as shown by use of the specific JAK3 inhibitor WHI-P31. In basal culture conditions, CD40 signaling could be induced by the transient establishment of inter-fibroblastic CD40/CD40 ligand (CD40L) functional bridges. Indeed, powerful pro-inflammatory stimuli such as lipopolysaccharide and thrombin can rapidly mobilize CD40L at the surface of lung myofibroblasts. These interactions are modified by IL-13, which triggers the formation of a new type of functional receptor (p-IL-4Ralpha /IL-13Ralpha 1/gamma c) and also the recruitment and the phosphorylation of JAK3. Treatment with JAK3 inhibitors blocks IL-13-induced phosphorylation of JAK2, TYK2 and STAT3, but not of JAK1 and STAT6. These data underline (1) the pivotal role of the gamma c chain, CD40/CD40L, JAK3 and IL-13 in the inflammatory-like activation of lung myofibroblasts, (2) the cell-type restraint effects of IL-13 on these cells, and (3) the potential usefulness of JAK3 inhibitors in the treatment of asthma.     

Diminished responses to IL-13 by human monocytes differentiated in vitro: role of the IL-13Ralpha1 chain and STAT6.

The primary IL-13 receptor complex on human monocytes is believed to be a heterodimer comprised of the IL-4R alpha chain and the IL-2R gamma chain (gamma(c))-like molecule, IL-13R alpha1. mRNA levels for IL-13R alpha1, but not IL-4R alpha, were markedly decreased in in vitro monocyte-derived macrophages (MDMac), and with increasing time of monocytes in culture correlated with the loss of IL-13 regulation of lipopolysaccharide-induced TNF-alpha production. Analysis of cell lines Daudi and THP-1 that differentially express gamma(c) and IL-13R alpha1 showed that IL-13 can activate STAT6 in IL-13R alpha1-positive THP-1 cells but not in gamma(c)-positive, IL-13R alpha1-negative Daudi cells. IL-13 activation of STAT6 was reduced in MDMac which was associated with diminished IL-13-induced expression of CD23 and MHC class II. However, with reduced IL-13R alpha1 expression and low nuclear STAT6 activity, some IL-13-induced responses were unaltered in magnitude in MDMac. In the absence of functional IL-13R alpha1 and gamma(c), IL-13 must signal through an alternative receptor complex on MDMac. Experiments with a blocking antibody to IL-4R alpha showed that this chain remains an essential component of the IL-13 receptor complex on MDMac.     

IL2RGbase: a database of γc-chain defects causing human X-SCID

X-linked severe combined immunodeficiency (X-SCID) is an immune disorder caused by mutations in the X-linked gene IL2RG, which encodes the common γ chain of the lymphocyte receptors for interleukin 2 (IL-2) and many other cytokines. A database of human X-SCID mutations (IL2RGbase) has been assembled, and this article summarizes the first 136 entries from unrelated patients.     

眼皮肤白化病Ⅳ型产前基因诊断及一种MATP基因新突变

目的 对3例眼皮肤白化病(oculocutaneous albinism,OCA)患儿进行分型诊断,并在此基础上开展OCA4产前基因诊断研究,为临床OCA遗传咨询和产前诊断提供指导.方法 应用聚合酶链反应及DNA序列测定技术,确定先证者及其父母的基因型后,取绒毛或羊水进行产前基因诊断.结果 3例患儿均为OCA4.家系1患儿母亲后来两次怀孕,第1次诊断为患儿,已选择流产,再次怀孕时诊断为父源G349R致病基因携带者.家系2产前诊断结果显示胎儿既未获得父源突变,也未获得母源突变.家系3产前诊断结果显示胎儿仅获得父源G349R突变.结论 检出MATP基因3种已报道的OCA4致病性突变G349R、D160H和P419L,发现1种致病性新突变c,870delC.

Abstract：

Objective To provide guidance for clinical genetic counseling and prenatal diagnosis of oculocutaneous albinism (OCA) in China. Methods PCR and automatic DNA sequencing were applied to obtain the genotypes of the patients and their parents in three Chinese albinism families. Prenatal gene diagnoses were performed at early pregnancy by chorionic villus sampling (CVS) or by amniocentesis at midpregnancy. Results The three patients were all OCA4, whose genotypes were G349R/c. 870delC, G349R/P419L, G349R/D160H, respectively. The three couples had been diagnosed as carriers. In family 1, the first fetus was diagnosed as affected. Termination of pregnancy was opted following genetic counseling. The second fetus (monozygotic twin) was heterozygous only with the paternal G349R mutation. The fetus in family 2 did not get either one of the two mutations. The fetus in family 3 was heterozygous only with the paternal G349R mutation. Conclusion This study detected three reported pathogenic mutations of the membrane associated transporter protein gene (MATP), including G349R, D160H and P419L, and identified a novel pathogenic mutation c. 870delC. The prenatal gene diagnosis of OCA4 will be important to prevent the birth of affected child.     

IL-7 receptor deficient SCID with a unique intronic mutation and post-transplant autoimmunity due to chronic GVHD

Severe combined immunodeficiency (SCID) may result from a variety of genetic defects that impair the development of T cells. Signaling mediated by the cytokine interleukin-7 is essential for the differentiation of T cells from lymphoid progenitors, and mutations of either the interleukin-7 receptor alpha chain (IL-7Ralpha) or its associated cytokine receptor chain, the common gamma chain (gammac), result in SCID. Here we report a case of SCID due to heterozygous mutations of the IL7R gene encoding IL-7Ralpha. A previously unrecognized mutation found within intron 3 created a new exon between exons 3 and 4 in the mRNA transcribed from this allele, producing a truncated, unstable mRNA. This mutation illustrates the necessity of evaluating both coding and non-coding regions of genes when searching for pathogenic mutations. Following hematopoietic stem cell transplantation of our patient, immune reconstitution was accompanied by two unusual complications, immune-mediated myositis and myasthenia gravis.     

A novel IL2RG mutation associated with maternal T lymphocyte engraftment in a patient with severe combined immunodeficiency

Severe combined immunodeficiency (SCID) represents a genetically heterogeneous group of primary immunodeficiency disorders. Irrespective of the genetic defect, patients with SCID may be engrafted with transplacentally derived maternal T-lymphocytes that in a subset of cases may be responsive to phytohemagglutinin. Here, we present, from a genetic perspective, an SCID patient who not only harbored a novel mutation in the gene encoding the common chain (c) of the IL-2 receptor (IL2RG), but also carried reactive maternal T lymphocytes that produced a karyotype that was initially perplexing.     

Clonally expanded CD3+, CD4-, CD8- cells bearing the alpha/beta or the gamma/delta T-cell receptor in patients with the lymphoproliferative disease of granular lymphocytes.

Among 60 retrospectively assessed patients with the lymphoproliferative disease of granular lymphocytes (LDGL), lymphocytes from only 2 patients had the CD3+, CD4-, CD8- phenotype, rarely observed in normal peripheral blood lymphocytes (about 3%). In this paper we report a detailed study of lymphocytes isolated from these two patients. The cells from patients 1 had the CD3+, CD4-, CD8-, WT31-, beta F1-, TCR delta 1+, Ti gamma A-, BB3+, CD7+, CD16-, CD57+ phenotype, while cells from patient 2 had a phenotype even more rarely observed on normal lymphocytes: CD3+, CD4-, CD8-, WT31+, beta F1+, TCR delta 1-, CD7+, CD16-, CD57+. Thus, in only the first case the cells expressed the gamma/delta T-cell receptor (TCR) on the membrane, while the cells from the second case had the alpha/beta TCR. Genetic studies showed that in case 1 the TCR gamma gene was rearranged and the beta chain gene configuration was germline; the TCR mRNA was of normal size for the gamma chain, while that of the beta chain was truncated. Case 2 had the beta and the gamma genes of the TCR rearranged, but only the alpha and beta mRNA were expressed. In agreement with these findings, the delta chain gene of the TCR was rearranged in case 1 and was deleted in case 2. Cytotoxic activity was absent in cells from case 1 and low in case 2; in the latter, the lytic activity could be up-regulated following incubation with IL-2 or an anti-CD3 monoclonal antibody. Our study indicates that CD3+, CD4-, CD8- lymphocytes are rarely expanded in patients with LDGL. The detection of a lymphoproliferative disease of a CD3+, CD4-, CD8-, alpha/beta + cell may contribute to a better characterization of this novel lymphocytic subpopulation.