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We have studied immunological reconstitution following partially HLA-incompatible T cell depleted bone marrow transplantation, compared with reconstitution following HLA identical T cell depleted and HLA identical untreated bone marrow transplantation. We often observed an early emergence of E-rosette forming cells that were T3 negative and displayed strong natural killer activity in the first group of patients. This activity was shown with fresh leucocytes as well as interleukin 2 grown cells. The appearance of T3+ cells was delayed in this situation compared to that observed in HLA Identical bone marrow transplantation. The delay in T3+ cell differentiation and in cellular immune function development probably explains why NK rosette forming cells are early detected within 3-4 months following HLA mismatched bone marrow transplantation. This NK subset is likely to be present at an early stage in all types of bone marrow transplantation, but is most commonly observed simultaneously with the T3+ cells in HLA identical untreated bone marrow transplantation. The respective role of T cell depletion and HLA incompatibility in this phenomenon are discussed while patients' conditioning, cyclosporine A and graft-versus-host disease have been shown to be irrelevant for the dissociation between NK E-rosette forming cells and T3+ subset onsets. [ABSTRACT FROM AUTHOR]

Abstract Background Adverse reactions induced by BCG vaccination are rare, disseminated mycobacterial BCG infection in particular, which is often fatal and results from impaired immunity. The aim of this study is to determine the nature of the immunodeficiences in patients with disseminated BCG infection in northwest region of Iran. Materials and methods Through 2 years all infants with BCG adenitis or other complications of this vaccine that had suspicious BCG infection were referred to children's hospital and health centers of Tabriz. Evaluation of immune system and in some cases genetic survey was performed in infants with evidence of histopathologic demonstration of acid-fast bacilli. Then frequency of infants who had disseminated BCG infection with immunodeficiency was defined. Results From 48 selected infants with complications of BCG vaccine in the range of 2 to 62 months, 28 infants (58.3%) were male and 20 infants (41.7%) were female. Disseminated BCG infection was diagnosed in 11 cases, almost all of whom had immunodeficiency as follows: Seven cases had severe combined immunodeficiency and one cases had chronic granulomatous disease. MSMD in two cases and IL12 R deficiency in another one was diagnosed. Overall, the mortality rate was 72.8% (8 cases) which 7 cases of them were SCID and another one CGD Consanguineous was found in more than half (7 cases) of patients and family history of disseminated BCG infection or immunodeficiency was found in nearly one third (3 cases) of patients. Discussion BCG vaccine is administered world wide to prevent tuberculosis and is considered to have excellent safety profile. However in some immunodeficient patients it can cause severe and fatal complications, like in our region, where all cases of disseminated BCG infection with severe immunodeficiency died. Conclusion BCG vaccination is necessary in some countries such as Iran, so it seems that development of a more safer vaccine and change of vaccine program in the families with history of inherited immunodeficiency can be identifies such high risk infants and prophylaxis of severe complications or dead in such patients.

Background: DNA-dependent protein kinase catalytic subunit (DNA-PKcs) has an essential role in the non-homologous end-joining pathway that repairs DNA double-strand breaks in V(D)J recombination involved in the expression of T- and B-cell receptors. Whereas homozygous mutations in PRKDC define the scid mouse, a model that has been widely used in biology, human mutations in PRKDC are extremely rare and the disease spectrum has not been described so far., Objective: To provide an update on the genetics, clinical spectrum, immunological profile, and therapy of DNA-PKcs deficiency in human., Methods: The clinical, biological, and treatment data from the 6 cases published to date and from 1 new patient were obtained and analyzed. Rubella PCR was performed on available granuloma material., Results: We report on 7 patients; Six patients displayed the autosomal recessive p.L3062R mutation in PRKDC gene encoding DNA-PKcs. Atypical severe combined immunodeficiency with inflammatory lesions, granulomas, and autoimmunity was the predominant clinical manifestation (n=5/7). Rubella viral strain was detected in the granuloma of 1 patient over the 2 tested. T-cell counts, including naïve CD4 + CD45RA + T cells and T-cell function were low at diagnosis for 6 patients. For most patients with available values naïve CD4 + CD45RA + T cells decreased over time (n=5/6). Hematopoietic stem cell transplantation (HSCT) was performed in 5 patients, of whom 4 are still alive without transplant-related morbidity. Sustained T- and B-cell reconstitution was respectively observed for 4 and 3 patients, after a median follow-up of 8 years (range 3-16 y)., Conclusion: DNA-PKcs deficiency mainly manifests as an inflammatory disease with granuloma and autoimmune features, along with severe infections., (Copyright © 2024. Published by Elsevier Inc.)

Genetic heterogeneity in Nijmegen breakage syndrome (NBS) is highlighted by patients showing clinical and cellular features of NBS but with no mutations in NBS1 and normal levels of nibrin. NBS is an autosomal recessive disorder, whose clinical cellular signs include growth and developmental defects, dysmorphic facies, immunodeficiency, cancer predisposition, chromosomal instability and radiosensitivity. NBS is caused by mutations in the NBS1 gene, whose product is part of the MRE11/RAD50/NBS1 complex involved in the DNA double-strand break (DSB) response pathway. Since the identification of the NBS1 gene, patients with NBS clinical signs, particularly severe congenital microcephaly, are screened for mutations in the NBS1 gene. Further analyses include X-ray-induced chromosome aberrations, telomere analysis, kinetics of DSBs repair, levels of a panel of proteins involved in the maintenance of genetic stability, radiation-induced phosphorylation of various substrates and cell cycle analysis. We describe a patient with a NBS clinical phenotype, chromosomal sensitivity to X-rays but without mutations in the whole NBS1 or in the Cernunnos gene. Enhanced response to irradiation was mediated neither by DSBs rejoining defects nor by the NBS/AT-dependent DNA-damage response pathway. Notably, we found that primary fibroblasts from this patient displayed telomere length alterations. Cross-talk between pathways controlling response to DSBs and those involved in maintaining telomeres has been shown in the present patient. Dissecting the cellular phenotype of radiosensitive NBS-like patients represents a useful tool for the research of new genes involved in the cellular response to DSBs.

Both TCRA alleles are rearranged in mature T lymphocytes, as a result of a lack of allelic exclusion at the TRCA locus. We show in a series of T cell clones that the two TCRJA segments are not randomly, but rather coincidentally, rearranged in a given T cell. The TCRJA coincidence relies, in part, on the presence of "T early alpha" (TEA), a cis-regulatory genetic element located upstream of the TCRJA cluster. TEA promotes specific recombinational accessibility that targets primary TCRVAJA rearrangements on the 5' side of the TCRA locus. In a model of multiple waves of TCRVAJA recombination, this cis-regulatory effect of TEA allows for the scanning of the entire TCRJA cluster, thereby increasing the TCR alpha/beta diversity potential.

Omenn syndrome (OS) is an inherited disorder characterized by an absence of circulating B cells and an infiltration of the skin and the intestine by activated oligoclonal T lymphocytes, indicating that a profound defect in the lymphoid developmental program could be accountable for this condition. Inherited mutations in either the recombination activating genes RAG1 or RAG2, resulting in partial V(D)J recombinase activity, were shown to be responsible for OS. This study reports on the characterization of new RAG1/2 gene mutations in a series of 9 patients with OS. Given the occurrence of the same mutations in patients with T-B-severe combined immune deficiency or OS on 3 separate occasions, the proposal is made that an additional factor may be required in certain circumstances for the development of the Omenn phenotype. The nature of this factor is discussed.

The V(D)J recombination process insures the somatic diversification of immunoglobulin and antigen T cell receptor encoding genes. This reaction is initiated by a DNA double-strand break (dsb), which is resolved by the ubiquitously expressed DNA repair machinery. Human T-B-severe combined immunodeficiency associated with increased cellular radiosensitivity (RS-SCID) is characterized by a defect in the V(D)J recombination leading to an early arrest of both B and T cell maturation. We previously mapped the disease-related locus to the short arm of chromosome 10. We herein describe the cloning of the gene encoding a novel protein involved in V(D)J recombination/DNA repair, Artemis, whose mutations cause human RS-SCID. Protein sequence analysis strongly suggests that Artemis belongs to the metallo-beta-lactamase superfamily.

V(D)J recombination, accountable for the diversity of T cell receptor- and immunoglobulin-encoding genes, is initiated by a lymphoid-specific DNA double-strand break. The general DNA repair machinery is responsible for the resolution of this break. Any defect in one of the known components of the DNA repair/V(D)J recombination machinery (Ku70, Ku80, DNA-PKcs, XRCC4 and DNA ligase IV) leads to abortion of the V(D)J rearrangement process, early block in both T and B cell maturation, and ultimately to severe combined immune deficiency (SCID) in several animal models. A human SCID condition is also characterized by an absence of mature T and B lymphocytes, and is associated with an increase in sensitivity to DNA-damaging agents (RS-SCID). None of the above-mentioned genes are defective in these patients, arguing for the likelihood of the existence of yet another unknown component of the V(D)J recombination/DNA repair apparatus. Athabascan-speaking (SCIDA) Navajo and Apache Native Americans have a very high incidence of T(-)B(-)SCID. The SCIDA locus is highly linked with markers on chromosome 10p, although the exact molecular defect has not been recognized in these patients. We show here that cells with the SCIDA defect are impaired in the DNA repair phase of V(D)J recombination similarly to RS-SCID, precisely an absence of V(D)J coding joint formation. Moreover, genotyping analysis in several RS-SCID families corroborates a linkage of the RS-SCID locus to the SCIDA region on chromosome 10p. These results demonstrate the presence of a new essential DNA repair/V(D)J recombination gene in this region, the mutation of which causes RS-SCID in humans.

Gene therapy offers an attractive option to the most severe forms of primary immunodeficiency diseases. Identification of disease associated genes as well as advances in the technology of gene transfer into hematopoietic progenitor cells have set the basis for the first clinical trials. Settings characterized by the potential for a selective advantage provided to transduced cells are the first diseases to target. The recent example of successful treatment of Severe Combined Immunodeficiency-X1 (gamma c deficiency) illustrates this potential.

TEA (T early alpha) is a genetic element located upstream of the TCR-Jalpha cluster. Thymocytes from mice carrying a targeted deletion of TEA do not rearrange their TCRalpha locus on a window spanning the first nine Jalpha segments. This led us to the hypothesis of TEA having a "rearrangement focusing" activity on the 5' side of the TCR-Jalpha region. We analyzed DNAseI and "phylogenetic" footprints within the TEA promoter in an attempt to identify trans-acting factors that could account for its regulatory function on DNA accessibility. One of these footprints corresponded to a putative DNA-binding site for an orphan nuclear receptor of the ROR / RZR family. The RORgammaT cDNA clone was isolated from a thymus library using a probe corresponding to the DNA-binding domain of RORgamma / TOR. RORgammaT is a thymus-specific isoform of RORgamma, expressed almost exclusively in immature double-positive thymocytes. RORgammaT binds, to the TEA promoter in vitro. Lastly, the expression of RORgammaT is stimulated in two situations that mimic activation through the pre-TCR and in which the thymocytes have their TCR-alpha locus in an "open", yet unrearranged DNA configuration. We propose that the expression of RORgammaT may be part of the pre-TCR activation cascade leading to the maturation of alpha / beta T cells and may participate in the regulation of DNA accessibility in the TCR-Jalpha locus.

Fas (CD95/Apo-1) mutations were previously reported as the genetic defect responsible for human lymphoproliferative syndrome associated with autoimmune manifestations (also known as autoimmune lymphoproliferative syndrome or Canale-Smith syndrome). We have identified 14 new heterozygous Fas mutations. Analysis of patients and families allow us to further dissect this syndrome with regards to the relationship between Fas mutations, inheritance pattern, and phenotype as observed on long-term follow-up. In vitro studies show that lymphocytes from all Fas mutant carriers exhibit a Fas-antibody-induced apoptosis defect. However, among the 8 inherited mutations, 4 of 4 Fas missense mutations were associated with high clinical penetrance, whereas 3 of 4 mutations leading to a truncated Fas product were associated with variable clinical penetrance. This suggests that a second defect, in another yet undefined factor involved in apoptosis and/or lymphoproliferation control, is necessary to induce full clinical expression of the disease. These results also indicate that the currently available antibody-mediated in vitro apoptosis assay does not necessarily reflect the in vivo ability of abnormal Fas molecules to trigger lymphocyte death. In addition, we found that lymphoproliferative manifestations resolved with age, whereas immunological disorders [ie, hypergammaglobulinemia and detection of TcR alphabeta(+) CD4(-) CD8(-) lymphocytes] persisted. This observation suggests that Fas-mediated apoptosis plays a more important role in lymphocyte homeostasis in early childhood than later on in life.

Severe immunodeficiency characterized by lymphopenia was found in two siblings, one of whom was examined in detail. The calcium flux, pattern of tyrosine phosphorylation of proteins, and interleukin 2 (IL-2) production and proliferation in response to mitogens suggested that the peripheral blood T cells activated normally. The peripheral blood T cells were shown to have an activated phenotype with increased expression of CD45RO+ and CD95/Fas. Increased spontaneous apoptosis occurred in unstimulated lymphocyte cultures. The elevated apoptosis was not due to alterations in expression or to mutations in Bcl-2, Bcl-X(L), or Flip, nor could the spontaneous apoptosis be prevented by blocking Fas, suggesting that it was independent of Fas signaling. This is the first inherited combined immunodeficiency associated with impaired lymphocyte survival. Fibroblasts derived from the patient showed appreciable radiosensitivity in clonal assays, but apoptosis was not elevated. Our results show that the fibroblasts represent a new radiosensitive phenotype not associated with cell cycle checkpoint defects, V(D)J recombination defects, or elevated chromosome breakage. We suggest that the affected gene plays a role in an undetermined damage response mechanism that results in elevated spontaneous apoptosis in lymphoid cells and radiosensitivity in fibroblasts.

The products of recombination activating gene (RAG)1 and RAG2 initiate the lymphoid-specific phase of the V(D)J recombination by creating a DNA double-strand break (dsb), leaving hairpin-sealed coding ends. The next step uses the general DNA repair machinery of the cells to resolve this dsb. Several genes involved in both V(D)J recombination and DNA repair have been identified through the analysis of in vitro mutants (Chinese hamster ovary cells) and in vivo situations of murine and equine severe combined immunodeficiency (scid). These studies lead to the description of the Ku-DNA-dependent protein kinase complex and the XRCC4 factor. A human SCID condition is characterized by an absence of B and T lymphocytes. One subset of these patients also demonstrates an increased sensitivity to the ionizing radiation of their fibroblasts and bone marrow precursor cells. This phenotype is accompanied by a profound defect in V(D)J recombination with a lack of coding joint formation, whereas signal joints are normal. Functional and genetic analyses distinguish these patients from the other recombination/repair mutants, and thus define a new group of mutants whose affected gene(s) is involved in sensitivity to ionizing radiation and V(D)J recombination.