Immune reconstitution after hematopoietic stem cell transplantation: gaining experience without losing naivety

In addition to lymphocyte phenotyping and functional assays, new tools are now available to monitor specific aspects of the immune response in the follow-up of hematopoietic stem cell transplantation: reconstitution of T-cell diversity (spectratyping or immunoscope), ex vivo thymic function by measuring "T-cell receptor rearrangement excision DNA circles" and antigen-specific T-cell responses (HLA tetramers). Combining these methods should contribute to improve our current knowledge of how the immune system is reconstituted in different settings of hematopoietic stem cell transplantation and how we could improve this recovery process.     

Intermethod discordance for alpha-fetoprotein measurements in Fanconi anemia

BACKGROUND: The significantly higher serum alpha-fetoprotein (AFP) in patients with Fanconi anemia (FA) than in non-FA aplastic patients has potential diagnostic utility, but the increase is method-dependent. The aim of this study was to compare five AFP assays on FA and non-FA samples and to investigate possible explanations for FA-specific discrepancies. METHODS: Two methods available in our laboratory (Kryptor and IMx) were compared on 59 FA and 27 non-FA patient samples. Kryptor, Immulite, Elecsys, Immuno-I, and Elsa-2 methods were then compared on 14 FA and 14 non-FA patient samples. The AFP glycosylation profile was analyzed by electrophoretic separation in a lectin-containing gel. RESULTS: With all six methods, AFP values were significantly higher in FA than in non-FA patients, but the diagnostic precision and optimal cutoff values varied. Indeed, two methods reached 100% sensitivity and specificity, but in other methods, one or both of these parameters were significantly <100%. Neither heterophilic antibodies nor a specific glycosylation profile was detected in FA samples. CONCLUSIONS: AFP results are method-dependent in FA. New methods must be evaluated before use in differential diagnosis of aplastic patients.     

A new HLA-Cw allele (Cw*1510), identified in a French Caucasian individual

A novel HLA-Cw*15 allele, Cw*1510, found in a French Caucasian bone marrow recipient is described. Nucleotide sequence of the new variant is identical to the common Cw*15021 DNA sequences except nucleotides at positions 32 and 61 of exon 2. While the first difference is silent, the second cause substitution of an Histidine by an Arginine at amino acid position 21 of the alpha1 heavy chain domain.     

Soluble MICA-NKG2D interaction upregulates IFN-γ production by activated CD3CD56 NK cells: Potential impact on chronic graft versus host disease

A soluble isoform of MHC class I chain-related molecule A (soluble MICA), generated by proteolytic shedding from the membrane-bound MICA of various tumor cells, has been shown to downregulate both the expression of natural killer group 2-member D receptor and the cytotoxic function of effectors cells and was postulated as a mechanism for tumor immune evasion. Its effect on the expression of cytokines by the effector cells remained unexplored. Here we demonstrate that the sMICA molecules upregulate interferon gamma expression by interleukin-12/interleukin-18-activated CD3⁻CD56⁺ natural killer cells, witnessing the pro-inflammatory effect of soluble MICA. Overall, these data are in line with our previous observations that the raised serum levels of soluble MICA, following allogeneic hematopoietic stem cell transplantation, confer susceptibility to and the presence of pre-transplantation anti-MICA antibodies in the patient’s serum confer protection against chronic graft versus host disease.     

Acute myeloid leukemia impairs natural killer cells through the formation of a deficient cytotoxic immunological synapse

Acute myeloid leukemia (AML) cells are killed by allogeneic NK cells. However, autologous NK cells from AML patients express decreased levels of activating receptors, and show reduced cytotoxicity. Here, we investigated how interactions between NK and AML cells might cause loss of NK‐cell activity in patients. Our results show that AML cell lines and primary blasts alter the NK‐cell phenotype, reducing their cytotoxic potential upon prolonged contact. Downregulation of NK‐cell‐activating receptors was contact‐dependent and correlated with conjugate formation. Time‐lapse imaging of HL60 AML cell line and NK‐cell interactions showed a high proportion of noncytolytic contacts. Studies of NK‐cell immunological synapses revealed a defect in lytic synapse formation. Namely, despite correct F‐actin and LFA‐1 recruitment, polarization of lytic granules toward primary blasts or AML cell lines was reduced. The NK–AML cell line synapses showed impairment of CD3ζ recruitment. Attempts to correct these synapse defects by cytokine stimulation of NK cells improved conjugate formation, but not granule polarization. Pretreatment of AML cell lines with the immunomodulating molecule lenalidomide significantly enhanced granule polarization. We speculate that combining immunomodulatory drugs and cytokines could increase AML cell sensitivity to autologous NK cells and reinforce the activity of allogeneic NK cells in adoptive immunotherapy.     

Cervicomediastinal magnetic resonance imaging in persistent or recurrent papillary thyroid carcinoma: clinical use and limits.

Cervicomediastinal magnetic resonance imaging (MRI) was evaluated in 13 consecutive persistent or recurrent papillary thyroid carcinoma (PTC) patients, previously treated by total thyroidectomy and radioiodine ablation. All had elevated thyroglobulin (Tg) levels and were therefore submitted to a new therapeutic radioiodine dose followed by a posttherapeutic whole-body scan (131I-WBS) and subsequent MRI. Patients with known distant metastases were excluded from the study. Group 1 included 7 patients with a negative 131I-WBS, whereas cervical and/or mediastinal 131I-uptake was evidenced in the other 6 patients (group 2). MRI was thus compared to 131I-WBS, and additionally in 8 reoperated cases, to histology. MRI was positive in 11 of 13 (85%) patients, corresponding to 23 of 55 (41.8%) histologically confirmed sites. In group 1, MRI was positive in 5 of 7 patients, with a sensitivity of 47% (15/32 histologically positive sites), allowing appropriate indication of surgery: 4 neck surgery, and 1 mediastinal dissection because of too distant lymph node foci. In group 2, MRI always showed more localization than 131I-WBS; histology was obtained in 3. Because all the foci located in the mediastinal area (0.8 to 1.8 cm) were histologically confirmed (7/7 sites), MRI avoided underestimation of surgery in the 8 reoperated patients. However, additional images were also observed corresponding to a normal thymus, a small neuroma or inflammatory lymph nodes, but pretracheal and very small nodes (less than 0.5 cm) were missed. In conclusion, although less specific than radioiodine scintigraphy, MRI can detect local persistent or recurrent PTC, and seems particularly effective for evaluation of mediastinal involvement.     

Epitope mapping of human monoclonal antibodies to HLA-B27 by using natural and mutated antigenic variants

The epitopes defined by three human monoclonal antibodies (mAbs) (Tr3B6, TrCG10, TrBH12) against HLA-B27 have been mapped by flow cytometry. For this purpose we used murine transfected cells expressing at their surface hybrid antigens between HLA-B7 and -B27 and, in addition, Epstein-Barr virus cells lines expressing the six HLA-B27 alleles B^*2701 to B^*2706. The results indicated that the mAbs are domain specific. TrBH12 recognizes the first external (alpha-1) domain. Residues critical for the TrBH12 epitope are located in the alpha-1 helix and include the polypeptide stretch 63–76 plus a critical amino acid at position 77. Tr3B6 binds the second external (alpha-2) domain, and one mutation (VAL¹⁵²→GLU¹⁵²) destroyed its epitope. TrCG10 also binds the alpha-2 domain.