Lynn D. Haynes

IL-17–dependent cellular immunity to collagen type V predisposes to obliterative bronchiolitis in human lung transplants

Bronchiolitis obliterans syndrome (BOS), a process of fibro-obliterative occlusion of the small airways in the transplanted lung, is the most common cause of lung transplant failure. We tested the role of cell-mediated immunity to collagen type V [col(V)] in this process. PBMC responses to col(II) and col(V) were monitored prospectively over a 7-year period. PBMCs from lung transplant recipients, but not from healthy controls or col(IV)-reactive Goodpastures syndrome patients after renal transplant, were frequently col(V) reactive. Col(V)-specific responses were dependent on both CD4+ T cells and monocytes and required both IL-17 and the monokines TNF-alpha and IL-1beta. Strong col(V)-specific responses were associated with substantially increased incidence and severity of BOS. Incidences of acute rejection, HLA-DR mismatched transplants, and induction of HLA-specific antibodies in the transplant recipient were not as strongly associated with a risk of BOS. These data suggest that while alloimmunity initiates lung transplant rejection, de novo autoimmunity mediated by col(V)-specific Th17 cells and monocyte/macrophage accessory cells ultimately causes progressive airway obliteration.

Tolerance to Noninherited Maternal MHC Antigens in Mice

The phenomenon of tolerance to noninherited maternal Ags (NIMA) is poorly understood. To analyze the NIMA effect C57BL/6 (H-2b/b) males were mated with B6D2F1 (H-2b/d) females, whereby 50% of the offspring are H-2b/b mice that have been exposed to maternal H-2d alloantigens. Controls were H-2b/b offspring of C57BL/6 mothers, either inbred C57BL/6 mice or F1 backcross mice from breedings with H-2b/d fathers. We found that 57% of the H-2b/b offspring of semiallogeneic (H-2b/d) mothers accepted fully allogeneic DBA/2 (H-2d/d) heart grafts for >180 days, while similar transplants were all rejected by day 11 in controls (p < 0.0004). Foster nursing studies showed that both oral and in utero exposure to NIMA are required for this tolerogenic effect. An effect of NIMA was also found to extend the survival of skin grafts from a semiallogeneic donor (p < 0.02). Pretransplant analysis of splenocytes showed a 40–90% reduction of IL-2-, IL-5-, and IFN-γ-producing T cells responding to H-2d-expressing APC in NIMAd-exposed vs control mice. Injection of pregnant BALB/c-dm2 (H-2Ld-negative) female mice i.v. with H-2Ld61–80 peptide profoundly suppressed the offspring’s indirect pathway alloreactive CD4+ T cell response to H-2Ld. These results suggest that the natural exposure of the fetus and newborn to maternal cells and/or soluble MHC Ags suppresses NIMA-allospecific T cells of the offspring, predisposing to organ transplant tolerance in adult mice.

Th-17, Monokines, Collagen Type V, and Primary Graft Dysfunction in Lung Transplantation

RATIONALE The pathogenesis of primary graft dysfunction (PGD), a serious complication of lung transplantation, is poorly understood. Human studies and rodent models have shown that collagen type V (col[V]), stimulates IL-17-dependent cellular immunity after lung transplantation. OBJECTIVES To determine whether patients with end-stage lung disease develop pretransplant col(V)-specific cellular immunity, and if so, the impact of this response on PGD. METHODS Trans-vivo delayed-type hypersensitivity (TV-DTH) assays were used to evaluate memory T-cell responses to col(V) in 55 patients awaiting lung transplantation. Pa(O(2))/Fi(O(2)) index data were used to assess PGD. Univariate risk factor analysis was performed to identify variables associated with PGD. Rats immunized with col(V) or irrelevant antigen underwent lung isografting to determine if prior anti-col(V) immunity triggers PGD in the absence of alloreactivity. MEASUREMENTS AND MAIN RESULTS We found that 58.8% (10/17) of patients with idiopathic pulmonary fibrosis, and 15.8% (6/38) of patients without idiopathic pulmonary fibrosis tested while on the wait list for a lung transplant were col(V) DTH positive. Col(V) reactivity was CD4(+) T-cell and monocyte mediated, and dependent on IL-17, IL-1beta, and tumor necrosis factor (TNF)-alpha. Pa(O(2))/Fi(O(2)) indices were impaired significantly 6-72 hours after transplantation in col(V)-reactive versus nonreactive patients. Univariate risk factor analysis identified only preoperative TV-DTH to col(V) and ischemic time as predictors of PGD. Finally, in a rat lung isograft model, col(V) sensitization resulted in significantly lower Pa(O(2))/Fi(O(2)), increased local TNF-alpha and IL-1beta production, and a moderate-to-severe bronchiolitis/vasculitis when compared with control isografts. CONCLUSIONS The data suggest that activation of innate immunity by col(V)-specific Th-17 memory cells represents a novel pathway to PGD after lung transplantation.

Developmental Exposure to Noninherited Maternal Antigens Induces CD4+ T Regulatory Cells: Relevance to Mechanism of Heart Allograft Tolerance

We hypothesize that developmental exposure to noninherited maternal Ags (NIMA) results in alloantigen-specific natural and adaptive T regulatory (TR) cells. We compared offspring exposed to maternal H-2d (NIMAd) with nonexposed controls. In vitro assays did not reveal any differences in T cell responses pretransplant. Adoptive transfer assays revealed lower lymphoproliferation and greater cell surface TGF-β expression on CD4+ T cells of NIMAd-exposed vs control splenocytes. NIMAd-exposed splenocytes exhibited bystander suppression of tetanus-specific delayed-type hypersensitivity responses, which was reversed with Abs to TGF-β and IL-10. Allospecific T effector cells were induced in all mice upon i.v. challenge with B6D2F1 splenocytes or a DBA/2 heart transplant, but were controlled in NIMAd-exposed mice by TR cells to varying degrees. Some (40%) NIMAd-exposed mice accepted a DBA/2 allograft while others (60%) rejected in delayed fashion. Rejector and acceptor NIMAd-exposed mice had reduced T effector responses and increased Foxp3+ TR cells (CD4+CD25+Foxp3+ TR) in spleen and lymph nodes compared with controls. The key features distinguishing NIMAd-exposed acceptors from all other mice were: 1) higher frequency of IL-10- and TGF-β-producing cells primarily in the CD4+CD25+ T cell subset within lymph nodes and allografts, 2) a suppressed delayed-type hypersensitivity response to B6D2F1 Ags, and 3) allografts enriched in LAP+, Foxp3+, and CD4+ T cells, with few CD8+ T cells. We conclude that the beneficial NIMA effect is due to induction of NIMA-specific TR cells during ontogeny. Their persistence in the adult, and the ability of the host to mobilize them to the graft, may determine whether NIMA-specific tolerance is achieved.

Human CD4+CD25low Adaptive T Regulatory Cells Suppress Delayed-Type Hypersensitivity during Transplant Tolerance

Adaptive T regulatory (TR) cells mediate the suppression of donor-specific, delayed-type hypersensitivity (DTH) in tolerant organ transplant recipients. We hypothesized that cells belonging to the CD4+CD25+ T cell subset but distinct from natural TR cells may fulfill this role. To test this hypothesis, PBMC and biopsy samples from two tolerant kidney transplant recipients (K1 and K2) were analyzed. When transferred with recipient APC into a SCID mouse footpad, CD4+ T cells were hyporesponsive in DTH to donor type HLA-B Ags and derivative allopeptides. However, anti-human TGF–β1 Ab revealed a response to immunodominant allopeptides in both patients, suggesting that CD4+ T effector (TE) cells coexisted with suppressive, TGF–β1-producing CD4+ TR cells. During in vitro culture, allopeptide stimulation induced both IFN-γ-producing and surface TGF–β1+ T cells. The relative strength of the latter response in patient K1 was inversely correlated with the level of systemic anti-donor DTH, which varied over a 6-year interval. Allopeptide-induced surface TGF–β1 expression was found primarily in Forkhead box P3 (FoxP3)–negative CD4+CD25low T cells, which could adoptively transfer suppression of donor-specific DTH. Biopsy samples contained numerous surface TGF-β1+ mononuclear cells that costained for CD4 and, less frequently CD25, but were negative for FoxP3. The CD4+TGF-β1+ T cells were localized primarily to the tubulointerstitium, whereas TGF-β1−FoxP3+CD25+ cells were found mainly in lymphoid aggregates. Thus, adaptive TR cells suppressing TE cell responses to donor allopeptides in two tolerant patients appear to be functionally and phenotypically distinct from CD4+CD25highFoxP3+ T cells.

Immune regulation and graft survival in kidney transplant recipients are both enhanced by human leukocyte antigen matching.

We hypothesized that donor/recipient sharing of the human leukocyte antigen (HLA) involved in allopeptide presentation to the T regulatory cell increases the incidence of immune regulation, thus contributing to long‐term graft survival. Peripheral blood mononuclear cells (PBMC) were obtained from 40 living related donor (LRD) and 31 cadaver renal transplant recipients. The trans vivo delayed type hypersensitivity (DTH) assay was used to assign patients to regulator, nonregulator, and sensitized categories. In a large cohort (n = 1934 patients), primary graft survival and rejection episodes were analyzed using a log rank test for comparison with the DTH results. The highest incidence of regulated anti‐donor DTH was observed in the LRD HLA‐identical group (6/6; 100%) followed by the LRD HLA 1 haplotype matched group (18/27; 67%). Within the cadaver population, two DR‐matched recipients had a higher frequency of regulated anti‐donor DTH (6/11; 55%) than 1 & 0 DR‐matched recipients (3/18; 17%). In a multivariate model, matching for HLA‐DR alone, or for DR plus DQ was significantly (p = 0.045, p = 0.041) correlated with DTH regulation. The better HLA‐matched groups showed the highest incidence of DTH regulation and, in a larger retrospective analysis, displayed better graft survival and freedom from acute rejection (p < 0.0001). HLA matching, and HLA‐DR matching in particular, correlates with the incidence of immune regulation after kidney transplantation.

Donor-Specific Indirect Pathway Analysis Reveals a B-Cell-Independent Signature which Reflects Outcomes in Kidney Transplant Recipients

To investigate the role of donor‐specific indirect pathway T cells in renal transplant tolerance, we analyzed responses in peripheral blood of 45 patients using the trans‐vivo delayed‐type hypersensitivity assay. Subjects were enrolled into five groups—identical twin, clinically tolerant (TOL), steroid monotherapy (MONO), standard immunosuppression (SI) and chronic rejection (CR)—based on transplant type, posttransplant immunosuppression and graft function. The indirect pathway was active in all groups except twins but distinct intergroup differences were evident, corresponding to clinical status. The antidonor indirect pathway T effector response increased across patient groups (TOL < MONO < SI < CR; p < 0.0001) whereas antidonor indirect pathway T regulatory response decreased (TOL > MONO = SI > CR; p < 0.005). This pattern differed from that seen in circulating naïve B‐cell numbers and in a cross‐platform biomarker analysis, where patients on monotherapy were not ranked closest to TOL patients, but rather were indistinguishable from chronically rejecting patients. Cross‐sectional analysis of the indirect pathway revealed a spectrum in T‐regulatory:T‐effector balance, ranging from TOL patients having predominantly regulatory responses to CR patients having predominantly effector responses. Therefore, the indirect pathway measurements reflect a distinct aspect of tolerance from the recently reported elevation of circulating naïve B cells, which was apparent only in recipients off immunosuppression.

Interleukin-17-dependent autoimmunity to collagen type v in atherosclerosis

Rationale: Considerable evidence shows atherosclerosis to be a chronic inflammatory disease in which immunity to self-antigens contributes to disease progression. We recently identified the collagen type V [col(V)] &agr;1(V) chain as a key autoantigen driving the Th17-dependent cellular immunity underlying another chronic inflammatory disease, obliterative bronchiolitis. Because specific induction of &agr;1(V) chains has previously been reported in human atheromas, we postulated involvement of col(V) autoimmunity in atherosclerosis. Objective: To determine whether col(V) autoimmunity may be involved in the pathogenesis of atherosclerosis. Methods and Results: Here, we demonstrate Th17-dependent anti-col(V) immunity to be characteristic of atherosclerosis in human coronary artery disease (CAD) patients and in apolipoprotein E–null (ApoE−/−) atherosclerotic mice. Responses were &agr;1(V)-specific in CAD with variable Th1 pathway involvement. In early atherosclerosis in ApoE−/− mice, anti-col(V) immunity was tempered by an interleukin (IL)-10–dependent mechanism. In support of a causal role for col(V) autoimmunity in the pathogenesis of atherosclerosis, col(V) sensitization of ApoE−/− mice on a regular chow diet overcame IL-10–mediated inhibition of col(V) autoimmunity, leading to increased atherosclerotic burden in these mice and local accumulation of IL-17–producing cells, particularly in the col(V)-rich adventitia subjacent to the atheromas. Conclusions: These findings establish col(V) as an autoantigen in human CAD and show col(V) autoimmunity to be a consistent feature in atherosclerosis in humans and mice. Furthermore, data are consistent with a causative role for col(V) in the pathogenesis of atherosclerosis.

Tolerance Induction or Sensitization in Mice Exposed to Noninherited Maternal Antigens (NIMA)

Developmental exposure to noninherited maternal antigens (NIMA) exerts a tolerizing or sensitizing influence on clinical transplantation in humans and experimental animals. The aim of this study was to determine if strain and gender differences influence the NIMA effect. Six different mouse strain backcross matings of F1 females with homozygous males (‘NIMA backcross’) and corresponding control breedings of F1 males with homozygous females were performed. H‐2 homozygous offspring underwent heterotopic heart transplantation from fully allogeneic donors expressing noninherited H‐2 antigens. A NIMA tolerizing effect on heart allograft outcome was found in three of six breeding models. In all three cases, the tolerizing antigens were from an H‐2d+ strain. The tolerogenic effect was greatest in male as compared with female recipients. Offspring from the three breeding models in which no tolerance was seen, appeared to be sensitized based on poorer graft survival, or enhanced T‐ or B‐cell responses to the noninherited H‐2b or k antigens. Significantly higher percentages of maternal antigen+ cells were found in the peripheral blood of tolerant versus nontolerant strains of backcross mice prior to transplant. Our findings imply that transplants are predisposed to tolerance or rejection due to recipient developmental history and immunogenetic background.

Reflux-Induced Collagen Type V Sensitization: Potential Mediator of Bronchiolitis Obliterans Syndrome

BACKGROUND Lung transplantation continues to have poor long-term survival partly because of the high incidence of bronchiolitis obliterans syndrome (BOS). Gastroesophageal reflux disease (GERD) has been implicated in BOS pathogenesis. We investigated the role of collagen type V [col(V)] sensitization in this process. METHODS Only primary lung transplant recipients were included. Reflux status was assessed with pH monitoring, impedance plethysmography, and esophagogastroduodenoscopy. Sensitivity to col(V) was determined with trans vivo delayed-type hypersensitivity reaction (DTH). Kaplan-Meier analyses were performed. RESULTS Of the 54 recipients, 26 had proven GERD. There were no significant between-group differences in diagnosis; donor and recipient age; sex; ischemic time; single vs bilateral; human leukocyte antigen A, B, and DR matching cytomegalovirus status; acute rejections; or mean follow-up period. The mean DTH response in the GERD group was 25.7 x 10(-4) inches vs 18.3 x 10(-4) inches in the non-GERD group (P = .023). There was a significant reduction in BOS-free survival in the GERD group for both BOS-I (GERD+, 28.3%; GERD-, 86.6%; P = .0001) and BOS-II/III (GERD+, 66.2%; GERD-, 91.7%; P = .0374). A second cohort of 53 patients awaiting lung transplantation also was assayed. The mean DTH response in the GERD group was 24.0 x 10(-4) inches vs 13.1 x 10(-4) inches in the non-GERD group (P = .003). There were no differences in age or sex. CONCLUSIONS GERD is strongly associated with the development of BOS after primary lung transplantation. Col(V) sensitization is associated with reflux and BOS and may play an intermediary role in the pathogenesis of BOS. Trials using col(V) reactivity to assess the impact of antireflux procedures in patients with lung transplantation and idiopathic pulmonary fibrosis are warranted.