[Natural cycle for frozen-thawed embryo transfer: Spontaneous ovulation or triggering by HCG]

OBJECTIVE

To compare frozen-thawed embryo transfer (FET) outcomes in natural cycles according to ovulation induction: spontaneous versus recombinant human chorionic gonadotrophin (r-hCG) triggering.

METHODS

This retrospective study included all patients monitored for natural cycle FET during one year. When serial monitoring were performed until spontaneous LH rise, patients were included in group A (n=38) whereas those receiving r-hCG for ovulation triggering formed group B (n=43). All embryos had been cryopreserved by a vitrification method following a previous IVF cycle. No luteal phase support had been given. We compared outcomes between the 2 groups.

RESULTS

After checking groups comparability, we didn't find significant difference for the implantation rate, clinical pregnancy rate and live birth (31% vs 45%, 32% vs 51% et 21% vs 32%, respectively for group A and B). The number of monitoring was significantly lower in group B (1,9±0,8 versus 2,5±1, P=0,006).

DISCUSSION

Although no consensus has been yet established, natural cycle seems indicated for normo-ovulating patients but the question of ovulation induction is still debated. In our study, triggering ovulation by r-hCG, respecting strict criteria, seems provide good results while reducing both protocol's constraints and cost.

Lack of evidence of a specific role for C4A gene deficiency in determining disease susceptibility among C4-deficient patients with systemic lupus erythematosus (SLE)

The aim of the present study was to investigate the prevalence of C4 and C2 deficiencies and to characterize genomic alterations in C4 genes in a large cohort of 125 unselected patients with SLE. We determined the protein concentration and functional activity of C2 and C4, as well as the C4 phenotype. C4 genotyping included Taq 1 restricted fragment lengh polymorphism (RFLP) analysis and polymerase chain reaction using sequence-specific primers (SSP-PCR). Type I C2 deficiency was diagnosed by PCR. Overall, 79.2% of the patients exhibited abnormalities of the C4 genes including deletion, non-expression, gene conversion and duplication. Among C4-deficient patients (n = 66, 52.8% prevalence), 41.0% of the patients exhibited a C4A deficiency and 59.0% a C4B deficiency. Half of the C4 deficiencies were due to a gene deletion. There was a strong association between C4A and C4B gene deletion and the presence of the DRB1*03 allele. Among the silent C4A genes, only two cases were related to a 2-bp insertion in exon 29 of the C4A gene. A gene conversion was demonstrated in eight patients (6.4%). One patient had a homozygous C4A deficiency. Three (2.4%) patients presented with a heterozygous type I C2 deficiency and none with homozygous deficiency. Our results argue against a specific role for C4A gene deficiency in determining disease susceptibility among patients with SLE that are C4-deficient.

Langerhans-like dendritic cells generated from cord blood progenitors internalize pollen allergens by macropinocytosis, and part of the molecules are processed and can activate autologous naive T lymphocytes

BACKGROUND

The safety and efficacy of sublingual immunotherapy have been demonstrated in moderate allergic asthma and seasonal rhinitis. However, not much is known about the precise mechanism of action of the allergen when it crosses the oral mucosa.

OBJECTIVE

To define this mechanism, we investigated the role of Langerhans' cells in the capture and internalization of allergens.

METHODS

We generated dendritic cells in vitro with the phenotypic characteristics of Langerhans-like dendritic cells (LLDCs) from cord blood CD34(+) progenitors. We used two recombinant major allergens: Bet v 1 and Phl p 1 labeled with FITC.

RESULTS

Internalization of allergens and control proteins was dose- and time-dependent and related to the immature state of the cells. LLDCs internalized allergens with a high efficiency in comparison with control molecules. Allergens were only internalized by macropinocytosis, as demonstrated by the use of various inhibitors. Addition of intracellular pH-modifying molecules indicated that only a part of the allergens was accumulated in acidic vesicles, whereas the majority remained in other cytoplasmic structures. Pulse-chase experiments calculated a half-life of 4 hours, suggesting that part of the molecules were not metabolized in the lysosome. Allergen internalization by LLDCs might be followed by processing in some experiments, as demonstrated by activation of autologous T lymphocytes in 4 of 9 experiments.

CONCLUSION

These elements showed that Langerhans' cells present in mucosa might play an active role in immune responses to allergens.

In vitro evaluation of the sensitization potential of weak contact allergens using langerhans-like dendritic cells and autologous T cells

Contact hypersensitivity is a major public health concern in most industrial countries, which is why predictive tests which could identify potential allergens are needed. We have established an in vitro approach for the detection of primary immune response. This model uses Langerhans-like dendritic cells (LLDC) derived from cord blood progenitors and autologous T lymphocytes, isolated from the same blood sample. Treatment of day 12-14 LLDC, with strong haptens trinitrobenzene sulfonic acid (TNP), fluorescein isothiocyanate (FITC) or Bandrowski's base (BB), results in the proliferation of T lymphocytes, whereas weak allergens and irritants, such as sodium dodecyl sulfate (SDS) are ineffective. The use of immature (day 8) LLDC and the addition of a 48 h stage of incubation after hapten contact, result in phenotypic maturation of LLDC in addition to lymphocyte activation in all the cultures with strong haptens. The 48 h stage of incubation, results in sensitization and in some cases the induction of T cell proliferation to citronellal (1/8), coumarine (1/8) and to a prohapten p-phenylenediamine (pPDA; 2/8). The phenotype of DC after 48 h of contact with a strong hapten, becomes that of mature DC (CD83(+), CD86(+) and HLA-DR(++)). With fragrance molecules, weak haptens and prohaptens, a comparable phenotype is observed only when T lymphocytes are activated. These data suggest that the unresponsiveness observed with weak haptens, may be the consequence on an incomplete maturation of LLDC.

Presence of circulating abnormal CD34+ progenitors in adult Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is related to the proliferation of cells, which are similar to Langerhans cells (LC) but possess many abnormal characteristics. Lesions are widespread and this fact suggests that LCH cells or their precursors are present in the blood of patients. In five adult patients, we have isolated and cultured CD34+ blood progenitors of dendritic cells. We studied their phenotype by flow cytometry and their functional properties in mixed culture with heterologous lymphocytes and with autologous lymphocytes in the presence of tri-nitro-phenyl antigen (TNP). The amount of CD34+ precursors was dramatically higher than controls but a high mortality occurred during the in vitro differentiation. The phenotype of surviving cells was similar to LC phenotype (CD1a+, CD83+, Lag+) but some of them expressed CD2. These cells were able to induce T cell proliferation in mixed culture. They could not initiate primary response to TNP, except in a patient treated with thalidomide. In our hands, these CD34+ cells may be precursors of LCH cells.

Human complement factor H deficiency associated with hemolytic uremic syndrome

This study reports on six cases of deficiency in the human complement regulatory protein Factor H (FH) in the context of an acute renal disease. Five of the cases were observed in children presenting with idiopathic hemolytic uremic syndrome (HUS). Two of the children exhibited a homozygous deficiency characterized by the absence of the 150-kD form of Factor H and the presence, upon immunoblotting, of the 42-kD Factor H-like protein 1 (FHL-1) and other FH-related protein (FHR) bands. Southern blot and PCR analysis of DNA of one patient with homozygous deficiency ruled out the presence of a large deletion of the FH gene as the underlying defect for the deficiency. The other four children presented with heterozygous deficiency and exhibited a normal immunoblotting pattern of proteins of the FH family. Factor H deficiency is the only complement deficiency associated with HUS. These observations suggest a role for FH and/or FH receptors in the pathogenesis of idiopathic HUS.

Chromosome methylation patterns during mammalian preimplantation development

DNA methylation patterns were evaluated during preimplantation mouse development by analyzing the binding of monoclonal antibody to 5-methylcytosine (5-MeC) on metaphase chromosomes. Specific chromosome patterns were observed in each cell stage. A banding pattern predominated in chromosomes at the one-cell stage. Banding was replaced at the two-cell stage by an asymmetrical labeling of the sister chromatids. Then, the proportion of asymmetrical chromosomes decreased by one-half at each cell division until the blastocyst stage, and chromosomes became progressively symmetrical and weakly labeled. Our results indicate that chromosome demethylation is associated with each DNA replication and suggest that a passive mechanism predominates during early development.

Evaluation of the capacity of dendritic cells derived from cord blood CD34+ precursors to present haptens to unsensitized autologous T cells in vitro

Langerhans cells play a key role in contact hypersensitivity reactions. The application of haptens on the skin leads to many modifications of these cells, including the increase of major histocompatibility complex II expression, allogeneic stimulation potency, and migration towards lymph nodes to activate T cells. Moreover, it has been shown that Langerhans cells cultured in vitro are able to prime naive T cells in response to hapten contact. From CD34+ progenitors present in cord blood, we generated dendritic cells of which some presented the phenotypic markers of Langerhans cells. We show that these cells are able to sensitize syngeneic naive (CD45RA+) T cells to haptens such as trinitrophenyl conjugate of trinitrobenzene sulfonic acid (TNP) and fluoroscein isothiocyanate. The response to TNP is higher than to fluoroscein isothiocyanate, whereas sodium dodecyl sulfate, an irritant molecule used as a control, never caused this effect. Phenotypic analysis of cellular suspensions and experiments of cell sorting lead to the conclusion that only CD1a+ cells are able to induce a primary response of syngeneic T cells to TNP or fluoroscein isothiocyanate. Furthermore, we have shown a close relationship between the differentiation state of dendritic cells and their ability to prime T lymphocytes. Dendritic cells are able to present haptens in an efficient manner between day 10 and 14 of culturing CD34+ progenitors, whereas they were efficient in presenting alloantigens from day 6 until after day 20. This dissociation suggests the need of an active metabolic process for hapten presentation in the direct treatment of dendritic cells with haptens. This model of hapten presentation was used for a panel of fragrance molecules and other molecules considered as weaker haptens than TNP and fluoroscein isothiocyanate.

IL-4 addition during differentiation of CD34 progenitors delays maturation of dendritic cells while promoting their survival

Dendritic cells (DC) are the most effective cells for antigen presentation in primary immune responses. Human cord blood CD34+ progenitors cultured in the presence of GM-CSF and TNF alpha generate a heterogeneous population of DC including Langerhans-like DC (LLDC) and monocytes. We describe here that IL-4 exerts different effecs in such culture according to the cells considered. Thus, IL-4 favors DC components at the expense of monocytic development, and permits long-time persistence of DC which can be maintained up to one month in culture. These results show an IL-4-dependent inhibition of proliferation and emergence of CD14+ cells. Notably, however, IL-4 also acts on the DC precursors. Thus, IL-4 enhances survival and delays maturation of LLDC from CD1a+ CD14- precursors. In addition, IL-4 also favors orientation of CD14+ CD1a- DC/monocyte precursors towards dermal-type CD1a+ DC. DC recovered from IL-4 treated cultures display reduced allostimulatory capacity, but this function is restored upon IL-4 weaning. Finally, a short (48h) IL-4 pulse is sufficient to favor DC development. The present study demonstrates that IL-4 positively regulates DC development at several levels on distinct precursor cells.