ICOS Gene Research Articles

Cytotoxic CD8+ Temra cells show loss of chromatin accessibility at genes associated with T cell activation.

As humans age, their memory T cell compartment expands due to the lifelong exposure to antigens. This expansion is characterized by terminally differentiated CD8+ T cells (Temra), which possess NK cell-like phenotype and are associated with chronic inflammatory conditions. Temra cells are predominantly driven by the sporadic reactivation of cytomegalovirus (CMV), yet their epigenomic patterns and cellular heterogeneity remain understudied. To address this gap, we correlated their gene expression profiles with chromatin openness and conducted single-cell transcriptome analysis, comparing them to other CD8+ subsets and CMV-responses. We confirmed that Temra cells exhibit high expression of genes associated with cytotoxicity and lower expression of costimulatory and chemokine genes. The data revealed that CMV-responsive CD8+ T cells (Tcmv) were predominantly derived from a mixed population of Temra and memory cells (Tcm/em) and shared their transcriptomic profiles. Using ATAC-seq analysis, we identified 1449 differentially accessible chromatin regions between CD8+ Temra and Tcm/em cells, of which only 127 sites gained chromatin accessibility in Temra cells. We further identified 51 gene loci, including costimulatory CD27, CD28, and ICOS genes, whose chromatin accessibility correlated with their gene expression. The differential chromatin regions Tcm/em cells were enriched in motifs that bind multiple transcriptional activators, such as Jun/Fos, NFkappaB, and STAT, whereas the open regions in Temra cells mainly contained binding sites of T-box transcription factors. Our single-cell analysis of CD8+CCR7loCD45RAhi sorted Temra population showed several subsets of Temra and NKT-like cells and CMC1+ Temra populations in older individuals that were shifted towards decreased cytotoxicity. Among CD8+CCR7loCD45RAhi sorted cells, we found a decreased proportion of IL7R+ Tcm/em-like and MAIT cells in individuals with high levels of CMV antibodies (CMVhi). These results shed new light on the molecular and cellular heterogeneity of CD8+ Temra cells and their relationship to aging and CMV infection.

CTLA-4 Haploinsufficiency Presenting as Extensive Enteropathy in a Patient With Very Early Onset Inflammatory Bowel Disease

Patients with very early onset inflammatory bowel disease (VEO-IBD) have a higher incidence of monogenic disease compared to older age groups. Age, alone, is a strong predictor for monogenic disease. We discuss a case of VEO-IBD in which the patient presented with severe and refractory enteropathy, leading to diagnosis of CTLA-4 haploinsufficiency. Genetic workup showed de novo heterozygous deletions of the CTLA-4 and ICOS genes. This case was unique, as the patient did not have the other manifestations commonly present with the disease. We advocate for early and routine genetic workup of VEO-IBD, as patients with monogenic IBD have high morbidity and mortality, if inadequately treated. Our patient did not respond to conventional treatment modalities and required targeted treatment with Abatacept, a CTLA-4 agonist.

Chromosome 2q33genetic polymorphisms in Tunisian endemic pemphigus foliaceus.

BackgroundSeveral studies have suggested that polymorphisms within genes encoding T‐lymphocyte immune regulating molecules: CD28, CTLA‐4, and ICOS, may alter the signaling process and subsequently could be involved in susceptibility to a broad spectrum of autoimmune diseases.MethodsThis study aimed to replicate associations between common polymorphisms in the 2q33.2 cluster and susceptibility to pemphigus foliaceus (PF) in the Tunisian population. We investigated seven polymorphisms: rs3116496 and rs1879877 (CD28), rs231775, rs3087243, and (AT)n repeat (CTLA4); rs11889031 and rs10932029 (ICOS) in a case–control study which enrolled 106 Tunisian PF patients and 205 matched healthy controls.ResultsWe confirmed the associations with CTLA4((AT)13, p = 0.00137, OR = 3.96 and (AT)20, p = 0.008, OR = 5.22; respectively) and ICOS genes (rs10932029>CT, p = 0.034, OR = 2.12 and rs10932029>TT, p = 0.04 and OR = 0.41).ConclusionOur results indicate that susceptibility to PF is located in the proximal and the distal 3′ flanking region of the CTLA4/ICOS promoter. These findings may open avenues to the treatment of patients with biological drugs targeting CTLA4/ICOS molecules, in a personalized manner to achieve more effective treatment.

Genetic diversity of CD14, CD28, CTLA-4 and ICOS gene promoter polymorphism in African and American sickle cell disease

Variable immune response to external stimuli remains a major concern in sickle cell disease (SCD), with such responses predicted to be contributors to disease pathogenesis. Elucidating the diversity of host genes contributing to immune response would assist to clarify differing outcomes among and between disease groups. We hypothesize that there is a significant interethnic diversity in the CD14 (rs2569190), CD28 (rs35593994), CTLA-4 (rs5742909) and ICOS (rs4404254) gene polymorphisms among and between SCD groups. We genotyped single nucleotide polymorphisms of the 4 loci among African and African American SCD and control groups and between SCD groups. In all, 375 individuals from Mali (145 SCD and 230 controls) and 700 DNA samples from the United States (321 SCD and 379 controls) were subjected to a PCR-RFLP assay. We found no intraethnic difference in genotypic and allelic frequencies of the 4 loci among Africans and African Americans, potentially significant in disease association studies, including a similar observation for interethnic frequencies of CD28, CTLA-4 and ICOS genes, but not CD14. The CD14 (rs2569190) gene promoter demonstrated a significant difference (p < 0.02) between African and African American SCD groups, with the mutant variant (−159 T/T) more frequent (p < 0.0002) in African American SCD (38.9% versus 26.2%). The higher frequency of CD14 mutants among African Americans without an accompanying defect in CD28, CTLA-4 and ICOS diversity possibly indicates a defective innate response, driven by CD14, is untethered to downstream T cell differentiation or effector function. Additionally, we show that CD28 (rs35593994) mutant variants have no impact on T cell differentiation, as the ICOS gene provides an alternative pathway to override this impairment. We conclude that in spite of the defect in CD14, T cell selection and differentiation is unimpeded and a robust adaptive immune response initiated.

Genetic variations within the CD40L immune stimulating gene predict outcome for mCRC patients treated with first-line FOLFIRI/bevacizumab: Data from FIRE-3 and TRIBE.

558 Background: The introduction of immunotherapy has significantly improved outcome in various tumors. Immune stimulating proteins exert an anti-tumor effect mainly through enhancing T-cell mediated immune response. Additionally, preliminary data suggest a major role of immune stimulating proteins in modulating angiogenesis. We therefore hypothesize that variations in genes involved in the immune activation pathway may predict outcome in pts with mCRC treated with first-line FOLFIRI/ bevacizumab (bev). Methods: The impact of 4 functional SNPs within the CD40L, Light, OX40L and ICOS genes on outcome was evaluated in 322 pts with mCRC treated with first-line FOLFIRI/bev in two randomized phase III trials. We used TRIBE as a discovery (n = 215) and FIRE-3 as a validation set (n = 107). One hundred twenty-nine pts treated with FOLFIRI/cetuximab (cet) served as a control cohort (FIRE-3). OncoArray, a custom array manufactured by Illumina was used for data extraction. Genomic DNA was extracted from blood. Results: Baseline characteristics: FOLFIRI/bev, discovery set (TRIBE), median PFS/OS/FU 9.7/26.2/48.9 mo; FOLFIRI/bev, validation set (FIRE-3), PFS/OS/FU 11.5/32.4/71.1 mo; FOLFIRI/cet, control set (FIRE-3) PFS/OS/FU 12.8//23.9/70.7 mo. The CD40L rs1126535 SNP showed significant association with OS. Pts in the discovery cohort harboring any T allele and treated with FOLFIRI/bev had a longer median OS compared to C/C carriers (27.9 vs. 20.0 mo) in both univariate (HR 1.83, 95% CI 1.19-2.81, p = 0.005) and multivariate analyses (HR 1.62, 95% CI 1.03-2.56, p = 0.038). Similarly, any T allele carriers in the validation cohort had a significantly longer median OS than those harboring a C/C genotype (40 vs. 19.0 mo) in the multivariate analysis (HR 2.80, 95% CI 1.05-7.50, p = 0.040). However, this association could not be shown in pts receiving FOLFIRI/cet (HR 0.60, 95% CI, 0.18-1.94, p = 0.38). Conclusions: We show for the first time that the CD40L polymorphism rs1126535 might serve as a predictive marker in pts with mCRC treated with FOLFIRI/bev. Targeting CD40L might be promising to further improve treatment against mCRC and to overcome resistance to anti-angiogenic therapy.

Abstract 2792: The combination of immune checkpoint blockers with the anti-ICOS KY1044 antibody results in a strong tumor response

Abstract The last few years have shown a strong paradigm shift in cancer therapies with the approval of antibodies targeting immune checkpoints (CTLA-4, PD-1 and PD-L1). These immune checkpoint blockers (ICBs) are associated with a strong and long-lasting response in patients suffering from different malignancies. However, there is still a high proportion of patients showing intrinsic or acquired resistance to ICBs. Although the mechanisms associated with the lack of immune response are multiple, the presence of highly anti-inflammatory regulatory T cells (TRegs) in the tumour microenvironment (TME) is known to negatively affect the response to these therapies. Similarly, high TReg levels in the TME have been associated with poor prognosis in several cancers. Together, this highlights the potential of targeting and depleting TRegs to enhance anti-tumour responses. The Inducible T-cell costimulator (ICOS/CD278) is related to the CD28 superfamily and is induced when T cells get activated. ICOS expression levels vary in different immune cell subtypes and in different tissues. In preclinical mouse tumour models, TRegs (CD4+/FOXP3+) constitutively express ICOS on their surface and the expression of ICOS on TRegs is significantly higher than that on effector T cells (TEffs). In addition, ICOS expression on TRegs is higher in the TME than in the blood or spleen, which makes it a strong candidate for preferential depletion of TRegs in tumours. By immunizing Kymice™ in which the endogenous Icos gene has been knocked out, we identified a novel, fully human antibody called KY1044 that cross-reacts with mouse ICOS. KY1044 is an anti-ICOS subclass G1 kappa monoclonal antibody that selectively binds to dimeric ICOS (Fc fusion) with an affinity of less than 2nM. Using in vitro and in vivo approaches we demonstrate that KY1044 has a dual mechanism of action: (1) it promotes the preferential depletion of intratumoural ICOShigh TRegs resulting in an increase in the TEff:TReg ratio in the TME; and (2) it stimulates ICOSLow TEff cells. Using the mouse effector enabled version of KY1044 (mIgG2a) we confirm, using syngeneic models, a strong anti-tumour efficacy as monotherapy or in combination with surrogates of ICBs. We also demonstrated a tumour antigen specific immunity, as highlighted by the rejection of the original tumour cells in animals cured of the disease and re-challenged by the same cell line. Noteworthy, Pharmacodynamic studies demonstrate long-term depletion of TRegs and a significant increase in the TEff:TReg ratio in response to KY1044. In summary, our data demonstrate that targeting ICOS with KY1044 is a valid approach for manipulating the immune system and for inducing a strong anti-tumour response in several indications. The data presented here also warrant the assessment of KY1044 in cancer patients in a clinical trial. Citation Format: Richard C. Sainson, Matthew McCourt, Anil Thotakura, Nahida Parveen, Miha Kismac, Gwenoline Borhis, Joana Carvalho, Tracey Myers, Robert Rowlands, Hanif Ali, Hannah Craig, Vivian Wong, Qi Liang, Volker Germaschewski. The combination of immune checkpoint blockers with the anti-ICOS KY1044 antibody results in a strong tumor response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2792.

Genetic Variation of Costimulatory Molecules, Including Cytotoxic T-Lymphocyte Antigen 4, Inducible T-Cell Costimulator, Cluster Differentiation 28, and Programmed Cell Death 1 Genes, in Iranian Patients With Leukemia.

There are limited studies about the possible relationship between genetic variations of costimulatory genes and susceptibility to hematologic malignancies like leukemia and lymphoma. This cross-sectional study included 59 leukemia patients. The polymorphisms of costimulatory molecules, including the CTLA-4 gene (-318 C/T, -1722 T/C, -1661 A/G, +49 A/G), PD-1 gene (1.3 A/G, 1.9 C/T), ICOS gene (1720 C/T), and CD28 gene (17 C/T), were analyzed by polymerase chain reaction-restriction fragment length polymorphism methods. Our results showed that the TT genotype and T allele of the CTLA-4 -318 T/C polymorphism, the AA genotype of CTLA-4 +49 A/G polymorphism, and the CT genotype of PD-1 1.9 C/T polymorphism were significantly higher in healthy controls (P < .05). However, the AG genotype of the CTLA-4 +49 A/G, the CC genotype of the PD-1 1.9 C/T, and the CT genotype of the CD28 +17C/T polymorphism were significantly increased in patients with leukemia (P < .05). When the genotype frequency of costimulatory genes was compared between different leukemia groups, we observed that the A allele of the CTLA-4 +49 A/G and the CC genotype and C allele of the CD28 +17 C/T polymorphism were significantly higher in patients with acute leukemia than in those with chronic leukemia (P < .05). Among leukemia patients, the AA genotype of CTLA-4 +49A/G polymorphism was significantly increased in patients with acute myeloid leukemia, whereas the AG genotype was more prevalent in patients with acute lymphoblastic leukemia (P < .05). We show for the first time that genetic variations of costimulatory molecules CTLA-4, CD28, and PD-1 may be associated with susceptibility of Iranian patients to leukemia.

CD28/CTLA-4/ICOS haplotypes confers susceptibility to Graves\u2019 disease and modulates clinical phenotype of disease

Graves’ disease, an autoimmune disease with heterogeneous symptoms including Graves’ orbitopathy, has a combined genetic/environmental background, where variations within CD28/CTLA-4/ICOS genes are considered as disease markers.Association of CD28c.17+3T>C(rs3116496), CTLA-4g.319C>T(rs5742909), CTLA-4c.49A>G(rs231775), CTLA-4g.*642AT(8_33), CT60(rs3087243), Jo31(rs11571302), ICOSc.1554+4GT(8_15) polymorphisms with susceptibility to Graves’ disease and clinical outcome was investigated. The study group comprised of 561 Polish Caucasians, including 172 unrelated Graves’ disease patients. CTLA-4c.49A>G, CTLA-4g.319C>T, and CT60 were genotyped by PCR–RFLP; Jo31 and CD28c.17+3C>T by minisequencing; CTLA-4g.*642AT(8_33) and ICOSc.1554+4GT(8_15)—PCR and fluorescence-based technique. CD28c.17+3T>C(rs3116496)T/CTLA-4g.319C>T(rs5742909)C/CTLA-4c.49A>G(rs231775)G/CTLA-4g.*642AT(8_33)(AT16–21)/CT60(rs3087243)G/Jo31(rs11571302)G/ICOSc.1554+4GT(8_15)(m) and TCA(AT<16)GT(m) haplotypes increased risk of Graves’ disease, especially in males, as well as overall Graves’ orbitopathy development with severe outcome. TCG(AT16–21)GG(l) haplotype increased risk of Graves’ disease and reduced the chance of successful medical treatment. Although this haplotype was mainly observed in patients without signs of Graves’ orbitopathy, if Graves’ orbitopathy developed it favored a Graves’ orbitopathy outcome. Haplotype TCA(AT>21)GT(m) increased Graves’ disease risk in women and, in all patients, was linked to Graves’ disease without Graves’ orbitopathy. TCG(AT<16)GG(m) haplotype was predominantly observed in patients without Graves’ orbitopathy, whereas TCA(AT16–21)GG(m) was absent in those patients. TCA(AT16–21)GG(m) occurred in patients with a mild Graves’ orbitopathy outcome. The marker CTLA-4g.*642AT(8_33) was the only independent Graves’ disease risk factor, whereas CT60 was an independent factor for disease progression. Sporadic Graves’ disease was related to presence of CTLA-4c.49A>G[A] and the rare CTLA-4g.319C>T[T] allele variant. Familial background of the disease was exclusively associated with CTLA-4g.*642AT(8_33)[AT>21]/[AT>21] genotype. CD28/CTLA-4/ICOS loci may confer inherited susceptibility to Graves’ disease or may be involved in susceptibility to Graves’ disease and play a pathogenetic role.

ICOS-dependent PI3K signaling in regulatory T cell development and function

Abstract Foxp3+ regulatory T cells (TR) are critical for maintaining immune tolerance and preventing inflammatory disease. Given their immunosuppressive capabilities, manipulation of TR function and/or abundance is a promising therapeutic strategy to either augment or inhibit immune responses in the context of disease. A detailed understanding of the key factors that control TR development, homeostasis, and function is essential for the successful application of TR-based therapies. Recent work suggests that inducible T cell costimulator (ICOS) signaling is required for maintenance of effector TR (eTR) cells, which migrate to peripheral sites of inflammation. ICOS ligation is most notably a potent activator of phosphatidylinositol 3-kinase (PI3K), however the key signaling pathways downstream of ICOS that support eTR have not been investigated. In order to study the role of ICOS-dependent PI3K signaling, we obtained mice that carry a knock-in mutation in the Icos gene that alters the cytoplasmic tail motif of the ICOS protein, thereby specifically abolishing ICOS-mediated PI3K activation (IcosY181F mice). The frequency of TR is reduced in these mice, as is the proliferation of ICOShi TR in secondary lymphoid organs. CD4+ IcosY181F cells have impaired regulation of downstream PI3K targets, including p-AKT, p-S6, and CD62L. IcosY181F mice develop more severe disease earlier than WT controls using a model of experimental autoimmune encephalomyelitis and have lower eTR frequencies at effector sites. Taken together, data from our lab suggest an important role for ICOS-mediated PI3K activation in the development, maintenance, and function of TR.

&lt;i&gt;ICOS&lt;/i&gt; gene polymorphisms in B-cell chronic lymphocytic leukemia in the Polish population

There is strong evidence that altered immunological function entails an increased risk of B-cell chronic lymphocytic leukemia (B-CLL). The main mechanism of an anti-tumor response depends on T-cell activation. Unlike the constitutively expressed CD28, inducible costimulatory molecule (ICOS) is expressed on the T-cell surface after activation. ICOS enhances all the basic T-cell responses to a foreign antigen, namely proliferation, secretion of lymphokines, the upregulation of molecules that mediate cell-cell interaction, and effective help for antibody secretion by B cells. ICOS is essential for both efficient interaction between T and B cells and normal antibody responses to T cell-dependent antigens. It does not upregulate the production of interleukin-2, but superinduces the synthesis of interleukin-10. Our previous results indicated the ICOS gene has a role as a susceptibility locus to B-CLL. Therefore an extended study was undertaken to evaluate the association between four ICOS polymorphisms (which were recently described as functional ones) and susceptibility to B-CLL in the Polish population. A case-control study of 296 individuals, including 146 B-CLL patients, was conducted on four polymorphisms in the ICOS gene. Genotyping of the polymorphisms ICOS ISV1+173T>C (rs10932029), ICOSc.1624C>T (rs10932037), ICOSc.2373G>C (rs4675379), and ICOSc.602A>C (rs10183087) was carried out using allelic discrimination methods with the TaqMan SNP Genotyping Assay. There were no statistically significant differences in the allele, genotype, or haplotype distributions between B-CLL patients and healthy controls for any of the investigated polymorphic markers in the ICOS gene. However, we noted that patients carrying genotype ICOS ISV1+173T>C [TT], ICOSc.602A>C [AA], ICOSc.1624C>T [CC], and ICOSc.2373G>C [GG] have a decreased frequency of progression to a higher Rai stage during 60-month follow-up (21.35% vs. 40.8%, p = 0.013) compared to other individuals. This indicates that the investigated polymorphisms do not modulate the risk of B-CLL in the Polish population, but are associated with disease dynamics, in particular with the time to Rai stage progression.

ICOS Gene Polymorphisms In B-Cell Chronic Lymphocytic Leukemia In a Polish Population.

AbstractAbstract 4614 Introduction:There is strong evidence that altered immunological function entails an increased risk of B-cell chronic lymphocytic leukemia (B-CLL). The main mechanism of an antitumor response depends on T-cell activation. Unlike the constitutively expressed CD28, inducible costimulatory molecule (ICOS) is expressed on the T-cell surface after activation. ICOS enhances all the basic T-cell responses to a foreign antigen, namely proliferation, secretion of lymphokines, the up-regulation of molecules that mediate cell-cell interaction, and effective help for antibody secretion by B cells. ICOS is essential for both efficient interaction between T and B cells and normal antibody responses to T cell-dependent antigens. It does not up-regulate the production of interleukin-2, but superinduces the synthesis of interleukin-10. Our previous results indicated a role of ICOS gene as a susceptibility locus to B-CLL. Therefore an extended study was undertaken to evaluate the association between four ICOS polymorphisms (which were recently described as functional ones) and susceptibility to B-CLL in a Polish population. Methods:A case-control study of 296 individuals including 146 B-CLL patients was conducted on four polymorphisms in the ICOS gene. Genotyping of the polymorphisms ICOSISV1+173T>C (rs10932029), ICOSc.1624C>T (rs10932037), ICOSc.2373G>C (rs4675379), and ICOSc.602A>C (rs10183087) was done using allelic discrimination methods with the TaqManÒ SNP Genotyping Assay. Results:There were no statistically significant differences in the allele, genotype, and haplotype distributions between B-CLL patients and healthy controls for any of the investigated polymorphic markers in the ICOS gene. However, we noted that patients carrying genotype ISV1+173T>C [TT], ICOSc.602A>C [AA], ICOSc.1624C>T [CC], and ICOSc.2373G>C [GG] have a decreased frequency of progression to a higher Rai stage during 60-month follow-up (21.35 vs. 40.8%, p=0.013) compared with other individuals. Conclusion:This study showed that the investigated polymorphisms do not modulate the risk of B-CLL in the Polish population, but are associated with disease dynamics in particular with the time to Rai stage progression. Disclosures:No relevant conflicts of interest to declare.

Association of T Cell Costimulatory and Downregulatory Gene Polymorphisms and Susceptibility to Multiple Myeloma.

Multiple myeloma (MM) is a B-lineage malignancy characterized by an accumulation of isotype-switched, immunoglobulin-producing monoclonal plasma cells. Additionaly phenotype and functional abnormalities of T cell are observed. The implication of T cells in the development of plasmocytoma has been shown in murine model. The study was undertaken to evaluate the association between polymorphisms of the genes encoding major T cell costimulatory (CD28, ICOS) and downregulatory (CTLA-4) molecules and susceptibility to MM in a Polish population. One hundred patients with MM and 202 healthy subjects were studied. Genomic DNA was isolated from whole frozen blood using the NucleoSpinR Blood kit. Allele identification was achieved by PCR amplification. The amplified product for SNP loci was purified and minisequenced using the commercial kit SNapShot (PE Applied Biosystems). The dinucleotide repeat polymorphism was studied by PCR and fluorescence based technique. The products were analyzed on the ABI PRISM 310 Genetic Analyzer (ABI PRISM 310 capillary electrophoresis system).We found an association of 49G in exon 1 and (AT)82 alleles in 3′untranslated region in the CTLA-4 gene with MM [p=0.018, OR=1.57, 95% CI=1.08–2.29 and p=0.0013, OR=1.85, 95% CI=1.27–2.72, respectively] while no association between T/C substitution in intron 3 of the CD28 gene, the dinucleotide (GT)n repeat polymorphism in intron 4 in ICOS gene and C/T base exchange in the promoter (position −318) in the CTLA-4 gene and MM was observed. Our results indicate that the A/G substitution in exon 1 and microsatelite polymorphism in the 3′untranslated region in the CTLA-4 gene might be a susceptibility locus for MM.The present study is the largest and comprehensive to date to evaluate the association between genetic polymorphisms of genes encoding T cell costimulatory and downregulatory molecules and susceptibility to MM.

Association of T-Cell Regulatory Gene Polymorphisms With Susceptibility to Gastric Mucosa-Associated Lymphoid Tissue Lymphoma

Helicobacter pylori infection and host susceptibility interact to develop gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and activation of specific T cells might play a crucial role in this process. Recent investigations show that the CTLA4, CD28, and ICOS genes are located on chromosome 2q33 and their polymorphisms confer susceptibility to infectious and immune diseases through deregulation of T-cell stimulation. We aimed to determine the role of CTLA4, CD28, and ICOS polymorphisms in gastric MALT lymphoma. Genotyping for CTLA4 (49 A/G, -318 C/T, and CT60 A/G), CD28 (IVS3+ 17T/C), and ICOS (c.602 A/C and c.1624C/T) was performed for 62 patients with gastric MALT lymphoma and compared with 250 unrelated healthy controls. H pylori infection was significantly higher in patients with gastric MALT lymphoma (90.3%) compared with controls (66.4%; P < .001). The CTLA4 -318 C/T genotype was associated with a lower risk of developing gastric MALT lymphoma (odds ratio [OR] = 0.3; P = .022), whereas CTLA4 49 G/G genotype was linked to a higher risk (OR = 4.1; P = .044). In patients with H pylori infection, CTLA4 49 G/G genotype was associated with an even higher risk (OR = 6.4; P = .047). Carriage of the tightly linked -318C -49G haplotype conferred a four-fold higher susceptibility to MALT lymphoma (OR = 4.2; P = .042). Complete remission after H pylori eradication was related to tumor stage but not to genotypes or haplotypes. These results indicate a genetic link of CTLA4 gene polymorphisms to development of gastric MALT lymphoma and indirectly support the crucial role of host activated T cells in the MALT lymphomagenesis.

Defective Induction of CTLA-4 in the NOD Mouse Is Controlled by the NOD Allele ofIdd3/IL-2and a Novel Locus (Ctex) Telomeric on Chromosome 1

Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), or CD152, is a negative regulator of T-cell activation and has been shown to be associated with autoimmune diseases. Previous work has demonstrated a defect in the expression of this molecule in nonobese diabetic (NOD) mice upon anti-CD3 stimulation in vitro. Using a genetic approach we here demonstrate that a novel locus (Ctex) telomeric on chromosome 1 together with the Idd3 (Il-2) gene confers optimal CTLA-4 expression upon CD3 activation of T-cells. Based on these data, we provide a model for how gene interaction between Idd3 (IL-2), Ctex, and Idd5.1 (Ctla-4) could confer susceptibility to autoimmune diabetes in the NOD mouse. Additionally, we showed that the Ctex and the Idd3 regions do not influence inducible T-cell costimulator (ICOS) protein expression in NOD mice. Instead, as previously shown, higher ICOS levels in NOD mice appear to be controlled by gene(s) in the Idd5.1 region, possibly a polymorphism in the Icos gene itself.

Genetic analysis of the 2q33 region containing CD28–CTLA4–ICOS genes: association with non‐Hodgkin's lymphoma

There is strong evidence that altered immunological function entails an increased risk of lymphoma, although the current knowledge of aetiological factors for lymphomas is limited. The CTLA4 gene encodes a receptor that provides a negative signal to the T-cell once an immune response is initiated and completed. We analysed the 2q33 chromosomal region harbouring CD28, CTLA4 and ICOS genes, which are closely linked and have related functions in immune regulation, for association in 100 non-Hodgkin's lymphoma (NHL) patients and in 128 healthy controls; both groups originated from Sardinia. There was a strong association of the CTLA4 49A and the 3'-untranslated region (AT)(82) alleles with NHL [odds ratio (OR) = 2, 95% confidence interval (CI) = 1.2-3.2, and OR = 1.6, 95% CI = 1.1-2.4 respectively]. CTLA4-318C:49A:(AT)(82) was the most represented haplotype in the studied population and was associated with NHL (P = 0.0029, OR = 1.76, 95% CI = 1.2-2.5). Strong linkage disequilibrium was detected between CD28, CTLA4 and ICOS and a 'common' haplotype was found very frequently among NHLs. However, no independent association between CD28, ICOS, D2S72 markers and NHL was observed. Our findings enable CTLA4 from adjacent functionally related genes as the true causative risk gene for NHL susceptibility at least in Sardinian patients.

The diabetes susceptibility locus Idd5.1 on mouse chromosome 1 regulates ICOS expression and modulates murine experimental autoimmune encephalomyelitis.

Linkage analysis and congenic mapping in NOD mice have identified a susceptibility locus for type 1 diabetes, Idd5.1 on mouse chromosome 1, which includes the Ctla4 and Icos genes. Besides type 1 diabetes, numerous autoimmune diseases have been mapped to a syntenic region on human chromosome 2q33. In this study we determined how the costimulatory molecules encoded by these genes contribute to the immunopathogenesis of experimental autoimmune encephalomyelitis (EAE). When we compared levels of expression of costimulatory molecules on T cells, we found higher ICOS and lower full-length CTLA-4 expression on activated NOD T cells compared with C57BL/6 (B6) and C57BL/10 (B10) T cells. Using NOD.B10 Idd5 congenic strains, we determined that a 2.1-Mb region controls the observed expression differences of ICOS. Although Idd5.1 congenic mice are resistant to diabetes, we found them more susceptible to myelin oligodendrocyte glycoprotein 35-55-induced EAE compared with NOD mice. Our data demonstrate that higher ICOS expression correlates with more IL-10 production by NOD-derived T cells, and this may be responsible for the less severe EAE in NOD mice compared with Idd5.1 congenic mice. Paradoxically, alleles at the Idd5.1 locus have opposite effects on two autoimmune diseases, diabetes and EAE. This may reflect differential roles for costimulatory pathways in inducing autoimmune responses depending upon the origin (tissue) of the target Ag.

Homozygous loss of ICOS is associated with adult-onset common variable immunodeficiency.

No genetic defect is known to cause common variable immunodeficiency (CVID), a heterogeneous human disorder leading to adult-onset panhypogammaglobulinemia. In a search for CVID candidate proteins, we found four of 32 patients to lack ICOS, the "inducible costimulator" on activated T cells, due to an inherited homozygous deletion in the ICOS gene. T cells from these individuals were normal with regard to subset distribution, activation, cytokine production and proliferation. In contrast, naive, switched and memory B cells were reduced. The phenotype of human ICOS deficiency, which differs in key aspects from that of the ICOS-/- mouse, suggests a critical involvement of ICOS in T cell help for late B cell differentiation, class-switching and memory B cell generation.