Resetting the Adaptive Immune System After Autologous Stem Cell Transplantation: Lessons from Responses to Vaccines

Abstract Abstract 4071 Introduction. Emerging trends emphasize the importance of both innate and adaptive immune system in the response against infections, and in the pathogenesis of autoimmune and graft-versus-host (GVHD) diseases. Pattern recognition receptors such as Toll-like receptors (TLRs) play a key role in the cross-talk between innate and adaptive immune system. TLRs belong to type I transmembrane glycoprotein receptor family and recognize pathogen-associated molecular patterns (PAMPs), such as common protein, carbohydrate or DNA/RNA pattern motifs. TLRs are also receptors for endogenous ligands and damaged tissue, suggesting that both pathogen-derived molecules and products of damaged tissue can trigger signals which are responsible for the regulation of innate and adaptive immune responses. Extracellular ligands are recognized by surface TLRs (TLR1,TLR2,TLR4,TLR5, and TLR6). Intracellular TLRs (TLR3,TLR7,TLR8 and TLR9) bind mainly to foreign nucleic acids and sometimes detect self DNA/RNA. Aim of the study. Very little is known about expression and function of TLRs in vivo in patients who underwent allogeneic stem cell transplantation (SCT). The aim of this study was to evaluate the expression of TLRs on lymphocytes and monocytes in relation to the onset of acute GVHD. Methods. The expression of TLRs on lymphocytes and monocytes was analysed by flow cytometry as mean fluorescence intensity at day +30 and at the onset of GVHD. Functional data were obtained by ELISA assay after TLRs activation. The cell supernatants were collected and assayed for TNF-alpha, IFN-gamma and MCP-1. Relative induction of these cytokines was calculated in relation with unstimulated controls. Results. We analyzed 17 healthy donors and 34 patients. Median age was 46 years (range, 22–64) and 22 patients were male. Acute GVHD developed in 19 patients (12 with grade >=2). Clinical and transplant characteristics did not differ in patients with and without GVHD. Lymphocytes and monocytes of patients with acute GVHD showed higher levels of TLR5 (3,5±2,3 vs1,9±1,6 p=0,03; 25,8±25,9 vs 9,0±5,0 p=0,02) and a decreased expression of TLR1 (2,5±2,8 vs 4,3±2,8 p=0,02; 21,4±21,9 vs 54,9±37,4 p=0,005) and TLR9 (63,8±30,4 vs 111,1±62,9 p=0,03; 85,3±73,9 vs 164,2±90,6 p=0,01). IFN-gamma relative induction post-stimulation of TLR2,3,4 and 9 was significantly decreased in patients with acute GVHD (p< 0,04). Conclusions. TLRs show a different profile of expression in patients with acute GVHD in comparison with patients without it. These results suggest that the innate immune response via TLRs activation could be involved in the development of GVHD. In particular, a decreased expression of TLR-9 (receptor of hypomethylated DNA) on lymphocytes and monocytes can promote TLR-7 activation, inducing type I interferons and other pro-inflammatory cytokines. TLR-1 and −5, which are ligands for bacterial cell wall, could also be involved in the pathogenesis of GVHD. Moreover, acute GVHD negatively correlates with IFN-gamma production upon TLR2,3,4 and 9 activation. The assessment of a larger number of patients could be useful to understand the complex interplay among pathogens, self or non-self DNA and RNA, and the immune system. Disclosures: No relevant conflicts of interest to declare.

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The Maternal Immune Response to in Utero Hematopoietic Stem Cell Transplantation.

Blood ◽

10.1182/blood.v114.22.64.64 ◽

2009 ◽

Vol 114 (22) ◽

pp. 64-64

Author(s):

Tippi MacKenzie ◽

Erin Jarvis ◽

Amar Nijagal ◽

Tom Le ◽

Marta Wegorzewska ◽

...

Keyword(s):

Immune Response ◽

Stem Cell ◽

Immune System ◽

B Cells ◽

Stem Cell Transplantation ◽

Cell Transplantation ◽

In Utero ◽

Wild Type ◽

Hematopoietic Stem ◽

Adaptive Immune

Abstract Abstract 64 In utero hematopoietic stem cell transplantation (IUHSCTx) is a promising treatment strategy for many congenital hematopoietic disorders such as immunodeficiencies. However, clinical applications have been hampered by lack of engraftment, possibly secondary to a host immune response. This has been a conundrum in the field, since the fetus can also be tolerized to allogeneic cells in some circumstances. We hypothesized that it is the maternal immune response which limits engraftment of in utero transplanted cells. Methods: Fetal BALB/c mice at 14 days' gestation were transplanted with age-matched fetal liver (FL) cells (2.5 × 106 cells/fetus) from allogeneic C57B6 mice and levels of circulating donor cell chimerism were determined serially starting at 4 weeks after in utero transplantation. Rates of engraftment (number of chimeric pups/number of surviving pups) and levels of chimerism (donor CD45 cells/total CD45 cells) were compared to controls in which animals were transplanted with congenic cells (C57B6 (CD45.2) fetal hosts transplanted with C57B6 (CD45.1) FL). In order to determine the role of the maternal adaptive immune system, immunodeficient BALB/c.Rag−/− mothers (deficient in T and B cells) were bred to wild type BALB/c males, such that the fetuses (BALB/c.Rag+/−) would be immunocompetent. These fetuses were transplanted with C57B6 FL and rates of engraftment and levels of chimerism in these transplants were compared to those in wild type allogeneic transplants. In order to determine whether the maternal influence is caused by maternal lymphocytes trafficking into the fetus, C57B6 (CD45.2) females were bred to C57B6 (CD45.1) males, such that the fetal cells (CD45.1+/CD45.2+) could be distinguished from maternal cells (CD45.1−/CD45.2+). Fetal blood and tissues were examined for the presence of maternal cells by flow cytometry at various gestational ages. Results: The rate of engraftment after IUHSCTx in control animals transplanted with congenic cells was 14/16 (88%) and average levels of chimerism were 9.9±8.4%. In contrast, the rate of engraftment in wild-type BALB/c fetuses transplanted with allogeneic B6 cells was 11/25 (44%; p<0.05 compared to congenic), and levels of chimerism were 21±19 (p=NS), confirming there is an adaptive immune response to fetal stem cell transplantation. As expected, chimeric animals were tolerant to the donor strain by mixed lymphocyte reaction while injected, non-chimeric animals were sensitized. However, in the absence of a maternal adaptive immune system, rates of chimerism (in immunocompetent BALB/c.Rag+/− pups) increased to 100% (n=10, p<0.05 compared to wild type allogeneic) and levels of chimerism were significantly higher (44±18, p<0.05). Levels of chimerism in engrafted animals declined over time after allogeneic transplantation but not after congenic transplantation, indicating there is a second, late phase immune response to allogeneic cells. However, chimerism levels did not decline in the BALB/c.Rag+/− recipients, suggesting that the maternal immune system has long-lasting effects on the success of fetal transplantation, perhaps by priming the host immune system. In our analysis of maternal/fetal cellular trafficking, we detected maternal lymphocytes in the blood of midgestation fetuses (14±7% at E12.5–E14.5, n=9) which declined gradually and was undetectable after birth. Lineage analysis demonstrated that 45±15 % of maternal cells are Gr-1+ granulocytes and 21±15% are B cells. Trafficking of maternal cells into the fetus was increased following fetal manipulation (injection of PBS < injection of allogeneic HSC). Conclusions: There is an adaptive immune response which limits early engraftment after in utero transplantation of allogeneic cells and leads to a gradual decline in levels of chimerism in engrafted animals. However, in the selective absence of maternal T and B cells, all fetuses transplanted with allogeneic FL cells show long-term, multilineage engraftment and demonstrate donor-specific tolerance. These results indicate that the maternal immune system plays a significant role in the success of fetal HSC transplantation. Cellular trafficking between the mother and fetus may be a mechanism by which maternal lymphocytes encounter cells transplanted into the fetus. Our findings have clinical implications in that the success of IUHSCTx may be improved by harvesting cells from the mother or HLA-matching cells to the mother. Disclosures: No relevant conflicts of interest to declare.

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Depletion of autoreactive immunologic memory followed by autologous hematopoietic stem cell transplantation in patients with refractory SLE induces long-term remission through de novo generation of a juvenile and tolerant immune system

Blood ◽

10.1182/blood-2008-07-168286 ◽

2009 ◽

Vol 113 (1) ◽

pp. 214-223 ◽

Cited By ~ 184

Author(s):

Tobias Alexander ◽

Andreas Thiel ◽

Oliver Rosen ◽

Gero Massenkeil ◽

Arne Sattler ◽

...

Keyword(s):

T Cells ◽

Stem Cell ◽

Immune System ◽

Hematopoietic Stem Cell Transplantation ◽

Stem Cell Transplantation ◽

Adaptive Immune System ◽

Immunologic Memory ◽

Hematopoietic Stem ◽

Adaptive Immune

Abstract Clinical trials have indicated that immunoablation followed by autologous hematopoietic stem cell transplantation (ASCT) has the potential to induce clinical remission in patients with refractory systemic lupus erythematosus (SLE), but the mechanisms have remained unclear. We now report the results of a single-center prospective study of long-term immune reconstitution after ASCT in 7 patients with SLE. The clinical remissions observed in these patients are accompanied by the depletion of autoreactive immunologic memory, reflected by the disappearance of pathogenic anti–double-stranded DNA (dsDNA) antibodies and protective antibodies in serum and a fundamental resetting of the adaptive immune system. The latter comprises recurrence of CD31+CD45RA+CD4+ T cells (recent thymic emigrants) with a doubling in absolute numbers compared with age-matched healthy controls at the 3-year follow-up (P = .016), the regeneration of thymic-derived FoxP3+ regulatory T cells, and normalization of peripheral T-cell receptor (TCR) repertoire usage. Likewise, responders exhibited normalization of the previously disturbed B-cell homeostasis with numeric recovery of the naive B-cell compartment within 1 year after ASCT. These data are the first to demonstrate that both depletion of the autoreactive immunologic memory and a profound resetting of the adaptive immune system are required to reestablish self-tolerance in SLE. This trial was registered at www.clinicaltrials.gov as #NCT00742300.

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