Chimerism in women with end stage renal diseases: Who's who?

Many sources of foreign or semi foreign cells, known as microchimerism (Mc), can be found in healthy individuals. We have recently shown in women with end stage renal disease (ESRD) that Mc frequencies and levels are exacerbated prior to kidney transplantation. Is Mc arising from pregnancy a protective factor for renal diseases explaining lower incidence in women? Is Mc helpful in slowing down disease progression? However, natural Mc is not the only actor as post blood transfusion Mc is also found at high levels in women with ESRD. The difficulty is therefore to distinguish the different types of Mc and this is made even more complicated when the recipient receives a potentially chimeric organ. What part does each source of chimerism play in disease and transplant fate, and can one decipher each role knowing that one chimerism may hide another?

Comparing HLA shared epitopes in French Caucasian patients with scleroderma.

Although many studies have analyzed HLA allele frequencies in several ethnic groups in patients with scleroderma (SSc), none has been done in French Caucasian patients and none has evaluated which one of the common amino acid sequences, (67)FLEDR(71), shared by HLA-DRB susceptibility alleles, or (71)TRAELDT(77), shared by HLA-DQB1 susceptibility alleles in SSc, was the most important to develop the disease. HLA-DRB and DQB typing was performed for a total of 468 healthy controls and 282 patients with SSc allowing FLEDR and TRAELDT analyses. Results were stratified according to patient's clinical subtypes and autoantibody status. Moreover, standardized HLA-DRß1 and DRß5 reverse transcriptase Taqman PCR assays were developed to quantify ß1 and ß5 mRNA in 20 subjects with HLA-DRB1*15 and/or DRB1*11 haplotypes. FLEDR motif is highly associated with diffuse SSc (χ(2) = 28.4, p<10-6) and with anti-topoisomerase antibody (ATA) production (χ(2) = 43.9, p<10-9) whereas TRAELDT association is weaker in both subgroups (χ(2) = 7.2, p = 0.027 and χ(2) = 14.6, p = 0.0007 respectively). Moreover, FLEDR motif- association among patients with diffuse SSc remains significant only in ATA subgroup. The risk to develop ATA positive SSc is higher with double dose FLEDR than single dose with respectively, adjusted standardised residuals of 5.1 and 2.6. The increase in FLEDR motif is mostly due to the higher frequency of HLA-DRB1*11 and DRB1*15 haplotypes. Furthermore, FLEDR is always carried by the most abundantly expressed ß chain: ß1 in HLA DRB1*11 haplotypes and ß5 in HLA-DRB1*15 haplotypes.In French Caucasian patients with SSc, FLEDR is the main presenting motif influencing ATA production in dcSSc. These results open a new field of potential therapeutic applications to interact with the FLEDR peptide binding groove and prevent ATA production, a hallmark of severity in SSc.

Male microchimerism at high levels in peripheral blood mononuclear cells from women with end stage renal disease before kidney transplantation.

Patients with end stage renal diseases (ESRD) are generally tested for donor chimerism after kidney transplantation for tolerance mechanism purposes. But, to our knowledge, no data are available on natural and/or iatrogenic microchimerism (Mc), deriving from pregnancy and/or blood transfusion, acquired prior to transplantation. In this context, we tested the prevalence of male Mc using a real time PCR assay for DYS14, a Y-chromosome specific sequence, in peripheral blood mononuclear cells (PBMC) from 55 women with ESRD, prior to their first kidney transplantation, and compared them with results from 82 healthy women. Male Mc was also quantified in 5 native kidney biopsies obtained two to four years prior to blood testing and in PBMC from 8 women collected after female kidney transplantation, several years after the initial blood testing. Women with ESRD showed statistically higher frequencies (62%) and quantities (98 genome equivalent cells per million of host cells, gEq/M) of male Mc in their PBMC than healthy women (16% and 0.3 gEq/M, p<0.00001 and p = 0.0005 respectively). Male Mc was increased in women with ESRD whether they had or not a history of male pregnancy and/or of blood transfusion. Three out of five renal biopsies obtained a few years prior to the blood test also contained Mc, but no correlation could be established between earlier Mc in a kidney and later presence in PBMC. Finally, several years after female kidney transplantation, male Mc was totally cleared from PBMC in all women tested but one. This intriguing and striking initial result of natural and iatrogenic male Mc persistence in peripheral blood from women with ESRD raises several hypotheses for the possible role of these cells in renal diseases. Further studies are needed to elucidate mechanisms of recruitment and persistence of Mc in women with ESRD.

Cells from a vanished twin as a source of microchimerism 40 years later.

We report the case of a 40-year-old man diagnosed with a scleroderma-like disease. Clinical similarities with graft versus host disease prompted initial testing for chimerism employing fluorescence in situ hybridization (FISH). Female cells were observed within peripheral blood mononuclear cells from the patient.Because maternal cells have been detected in healthy immunologically competent adults and patients with autoimmune conditions, we hypothesized that these cells were of maternal origin. Contrary to our expectations, HLA-specific quantitative PCR (QPCR) ruled out maternal microchimerism. However, HLA-specific QPCR testing was positive for the paternal HLA haplotype that the patient did not inherit. We reasoned that the most likely origin of chimerism with non-inherited paternal HLA alleles was from an unrecognized "vanished" twin. The patient had never received a blood transfusion.This report suggests that cells from a vanished twin are a possible source of chimerism. The frequency of chimerism from this source is not yet known and whether the scleroderma-like disease observed in the patient is anecdotal or implies a potential association with autoimmune disease remains to be elucidated.

How microchimerism can impart HLA susceptibility in patients with rheumatoid arthritis.

Rheumatoid arthritis, a chronic inflammatory joint disease, is strongly associated with HLA-DRB1*01 and *04 alleles that have in common similar 5-amino acid motifs in the third hypervariable region of DRB1 (QKRAA, QRRAA, RRRAA), the so called shared epitope (SE). Most patients with RA carry 1 or 2 doses of the SE, with particular genetic combinations at higher risk. In recent work we provided evidence that patients who lack HLA-DRB1*01 and/or *04 alleles can acquire RA susceptibility through fetal, maternal or iatrogenic microchimerism. We also discuss how Mc carrying HLA-DRB1*04 alleles is more likely to be present in the peripheral blood of RA patients compared to Mc carrying HLA-DRB1*01 alleles. We further analyze our results in light of the hierarchy for RA risk with different combinations of the SE. How Mc could contribute to RA susceptibility and whether it also contributes to the hierarchy of risk observed with particular combinations of SE-containing alleles is certainly the beginning of an intriguing story and may offer hope for future therapeutic and/or preventative interventions.

Male microchimerism and HLA compatibility in French women with sclerodema: a different profile in limited and diffuse subset.

OBJECTIVES: Male microchimerism (Mc) persisting from pregnancy has been found at greater frequencies and/or higher quantities in women with scleroderma (SSc) compared with controls, suggesting a possible role in disease development. Moreover, women with an HLA-compatible child have a higher risk to develop SSc. We tested the hypothesis, on our French SSc cohort, that women with lcSSc and dcSSc, two distinct clinical subsets, have a different profile in terms of Mc and HLA compatibility in families. METHODS: We studied 98 women (52 lcSSc and 46 dcSSc) for male Mc, by real-time PCR, in their whole blood and/or peripheral blood mononuclear cells (PBMC). Similarly, 91 matched healthy women were analysed. Complete HLA-DRB1 typing was obtained for 58 SSc and 68 control families (proband/children). RESULTS: Women with lcSSc (N = 50) had male Mc more often in their whole blood than women with dcSSc (N = 40, 20 vs 5%, P = 0.038), but not significantly more than controls. By contrast, women with dcSSc (N = 36) hold Mc more often in PBMC (25 vs 9%), but not significantly and have greater quantities than controls (N = 82, P = 0.048). This contrast is also visible in feto-maternal HLA-DRB1 compatibility, which was increased only among women with lcSSc (N = 33) compared with controls (N = 68, P = 0.003). CONCLUSION: For the first time, we showed that women with lcSSc and dcSSc hold male Mc in different blood compartments. Furthermore, a distinct pattern between the two SSc subtypes is observed for feto-maternal HLA-DRB1 compatibility. These results suggest a different mechanism behind each type of disease.