Defective production of soluble HLA-G molecules by peripheral blood monocytes in patients with asthma

BACKGROUND: HLA-G, a human nonclassic MHC class I molecule, is responsible for complex immunoinhibitory functions. HLA-G is expressed as membrane-bound and is secreted as soluble molecules by the peripheral blood CD14+ monocytes activated by IL-10. OBJECTIVE: It has been reported that LPS stimulation induces IL-10 production by PBMCs and that IL-10 levels are reduced in patients with severe asthma compared with patients with mild asthma and healthy subjects. The study was designed to investigate whether this impaired IL-10 production can affect the expression and the secretion of soluble HLA-G (sHLA-G)-1/HLA-G5 molecules. METHODS: We investigated the production of sHLA-G1/HLA-G5 and IL-10 by specific ELISAs in the culture supernatants of LPS-activated PBMCs from 24 healthy subjects and 20 patients with moderate to severe persistent asthma. RESULTS: LPS stimulation induced the secretion of IL-10 and sHLA-G1/HLA-G5 molecules in all healthy subjects, whereas in patients with asthma, the levels of IL-10 were significantly lower (P < .001) and the number of cultures exhibiting detectable sHLA-G1/HLA-G5 was reduced (7/20; P < .001). The addition of exogenous IL-10 to LPS-stimulated PBMCs from patients with asthma restored normal sHLA-G1/HLA-G5 production. CONCLUSION: Our data suggest that a specific deficit of IL-10 secretion in patients with asthma could prevent the normal production of sHLA-G1/HLA-G5 molecules. The reduction of immunosuppressive activity mediated by HLA-G could in turn contribute to the persistence of chronic airway inflammation in asthma.     

A monoclonal antibody (GF 22.1) detecting different patterns of HLA class I cross-reactivities at different dilutions

A murine cytotoxic monoclonal antibody (GF 22.1) was produced by Balb/c immunization with GRA human lymphoblastoid cells. HLA-A, B and C blanketing and SDS-PAGE analysis of the immunoprecipitate demonstrated MHC class I structures as the targets. Cytotoxic assays were performed with peripheral blood lymphocytes from 84 unrelated donors and from members of 15 families at different antibody dilutions. Statistical analysis was performed by Fisher test on each dilution separately and by Mann-Whitney U test on the dilutions taken all together. The data suggest the detection of a cross-reacting group (B15, A32, B17, B40/w41 and B21) with high affinity and the inclusion of other antigens (B12, B35, A2, B13, A11 and A24) with a lower affinity.     

Second transplantation using allogeneic peripheral blood stem cells in a β-thalassaemia major patient featuring stable mixed chimaerism

Allogeneic bone marrow transplantation (BMT) for β-thalassaemia major carries the risks of disease recurrence due to residual thalassaemic stem cells or true immune-mediated rejection. We report a thalassaemic patient who displayed stable mixed chimaerism with only 5% donor-derived cells for about 5 years after BMT. Displacement of host cells was accomplished by ambulatory non-myeloablative conditioning and allogeneic G-CSF mobilized peripheral blood stem cell transplantation from the same donor, resulting in full reconstitution. Patients featuring stable mixed chimaerism after BMT may benefit from allogeneic cell therapy with immunocompetent lymphocytes and stem cells, whilst avoiding supralethal conditioning.     

Second transplantation using allogeneic peripheral blood stem cells in a β-thalassaemia major patient featuring stable mixed chimaerism

Allogeneic bone marrow transplantation (BMT) for β-thalassaemia major carries the risks of disease recurrence due to residual thalassaemic stem cells or true immune-mediated rejection. We report a thalassaemic patient who displayed stable mixed chimaerism with only 5% donor-derived cells for about 5 years after BMT. Displacement of host cells was accomplished by ambulatory non-myeloablative conditioning and allogeneic G-CSF mobilized peripheral blood stem cell transplantation from the same donor, resulting in full reconstitution. Patients featuring stable mixed chimaerism after BMT may benefit from allogeneic cell therapy with immunocompetent lymphocytes and stem cells, whilst avoiding supralethal conditioning.     

HLA-G and inflammatory diseases

HLA-G antigens are non classical HLA-class I molecules characterized by a low allelic polymorphism, a limited tissue distribution and the presence of membrane bound and soluble isoforms. The HLA-G antigens were firstly detected in cytotrophoblast cells at the feto-maternal interface where they maintain a tolerogenic status between the mother and the semiallogenic fetus. Recently a variable expression of HLA-G molecules has been documented in several autoimmune diseases, viral infections, cancer diseases and transplantation. Overall the presence of HLA-G molecules in both membranes bound and soluble isoforms was associated with tolerogenic functions against innate and adaptative cellular responses. HLA-G antigens are able to affect the cytotoxicity of natural killer and CD8+ T cells, CD4+ T lymphocyte functions and dendritic cell maturation. In addition to the allelic polymorphism the HLA-G gene shows a deletion/insertion polymorphism of a 14 base pairs sequence (14bp) in the exon 8 at the 3' untranslated region. Several reports have associated the presence of the 14bp insertion allele (+14bp) to an unstable mRNA and a lower sHLA-G protein production, suggesting a different ability to counteract inflammation between genotypes. We reviewed the literature on the expression of HLA-G antigens in autoimmune and allergic diseases and the possible functional role of these molecules in counteracting inflammation.     

Restricted immunoglobulin VH region repertoire in chronic lymphocytic leukemia patients with autoimmune hemolytic anemia

Between 10% and 25% of chronic lymphocytic leukemia (CLL) patients have episodes of autoimmune hemolytic anemia (AIHA) during the course of their disease. The anti-erythrocyte autoantibodies in most cases are polyclonal and express a different heavy chain isotype than the malignant clone, indicating that they are secreted by normal autoreactive B lymphocytes. To further investigate the pathogenesis of the AIHA in CLL, we analyzed the lg heavy (H) chain variable region genes expressed by leukemic cells from CLL patients with and without AIHA. Two VH genes were preferentially expressed by the leukemic cells in the CLL cases with AIHA and were present in 9 of the 12 investigated cases. The 51p1/DP-10 gene was expressed in 5 of these cases and was absent in the control group of 12 consecutive CLL cases without AIHA, whereas the DP-50 gene was present in 4 CLL-AIHA cases and only once in the control CLL group. A strikingly similar H-chain CDR3 region that contained a single reading frame of the DXP4 DH gene segment, and N- encoded proline at the DH/JH boundary, and a tyrosine-rich region encoded by the JH6 gene segment was observed in four CLL-AIHA cases. The preferential expression of two VH gene segments and a particular CDR3 region by the leukemic cells of patients with AIHA suggests that the antibodies produced by the CLL cells are directly involved in the pathogenesis of the hemolytic anemia.