We have reported that lung allograft rejection involves an immune response to a native protein in the lung, type V collagen (col(V)), and that col(V)-induced oral tolerance prevented acute and chronic rejection. In support of these findings col(V) fragments were detected in allografts during rejection, but not in normal lungs. The purpose of the current study was to isolate and characterize col(V)-specific allograft-infiltrating T cells and to determine their contribution to the rejection response in vivo. Two col(V)-specific T cell lines, LT1 and LT3, were isolated from F344 (RT1^lv1) rat lung allografts during rejection that occurred after transplantation into WKY (RT1^l) recipients. Both cell lines, but not normal lung lymphocytes, proliferated in response to col(V). Neither LT1 nor LT3 proliferated in response to alloantigens. LT1 and LT3 were CD4⁺CD25⁻ and produced IFN-γ in response to col(V). Compared with normal CD4⁺ T cells, both cell lines expressed a limited V-β TCR repertoire. Each cell strongly expressed V-β 9 and 16, but differed in expression of other V-βs. Adoptive transfer of each cell line did not induce pathology in lungs of normal WKY rats. In contrast, adoptive transfer of LT1, but not LT3, caused marked peribronchiolar and perivascular inflammation in isograft (WKY) lungs and abrogated col(V)-induced oral tolerance to allograft (F344) lungs. Collectively, these data show that lung allograft rejection involves both allo- and autoimmune responses, and graft destruction that occurs during the rejection response may expose allograft-infiltrating T cells to potentially antigenic epitopes in col(V).

Immunity to collagen V [col(V)] contributes to lung ‘rejection.’ We hypothesized that ischemia reperfusion injury (IRI) associated with lung transplantation unmasks antigenic col(V) such that fresh and well-healed lung grafts have differential susceptibility to anti-col(V)-mediated injury; and expression of the autoimmune cytokines, IL-17 and IL-23, are associated with this process. Adoptive transfer of col(V)-reactive lymphocytes to WKY rats induced grade 2 rejection in fresh isografts, but induced worse pathology (grade 3) when transferred to isograft recipients 30 days post-transplantation. Immunhistochemistry detected col(V) in fresh and well-healed isografts but not native lungs. Hen egg lysozyme-reactive lymphocytes (HEL, control) did not induce lung disease in any group. Col(V), but not HEL, immunization induced transcripts for IL-17 and IL-23 (p19) in the cells utilized for adoptive transfer. Transcripts for IL-17 were upregulated in fresh, but not well-healed isografts after transfer of col(V)-reactive cells. These data show that IRI predisposes to anti-col(V)-mediated pathology; col(V)-reactive lymphocytes express IL-17 and IL-23; and anti-col(V)-mediated lung disease is associated with local expression of IL-17. Finally, because of similar histologic patterns, the pathology of clinical rejection may reflect the activity of autoimmunity to col(V) and/or alloimmunity.

Interactions between antigen-presenting cells and T cells can result in T cell activation or suppression. With the use of RNA analysis, high-performance liquid chromatography, mixed leukocyte reactions (MLRs), and animal models, the current study reports that lung interstitial antigen-presenting cells (iAPCs, CDllc+) suppress T cell responses in vitro and in vivo by production of indoleamine 2,3-dioxygenase (IDO), an enzyme that catabolizes tryptophan to its byproduct, kynurenine. IDO mRNA expression was unique to lung iAPCs, as cells similarly isolated from the liver and spleen did not express IDO constitutively, or in response to interferon-gamma. Lung iAPCs suppressed proliferation of allogeneic T cells, correlating with increased kynurenine levels; and blockade of IDO activity with 1-methyl-DL-tryptohan (1-MT) or addition of exogenous tryptophan recovered T cell proliferation in MLRs. In contrast, liver and splenic iAPCs were potent stimulators of T cells in MLRs, and IDO inhibition had no effect on T cell responses. In vivo studies showed that systemic blockade of IDO resulted in spontaneous proliferation in lung T cells and pulmonary inflammation. Finally, overexpressing IDO in lung transplants abrogated acute allograft rejection, a T cell-mediated disease. Collectively these data show that lung iAPCs contribute to local regulation of cellular immune responses by production of IDO.

A precise preoperative diagnosis of ‘very early’ lung carcinoma may identify patients who can undergo curative surgery with limited resections. Data from a multi-institutional project were collected on 1737 patients who had undergone limited resections (segmentectomy or wedge resection) for T1N0M0 non-small-cell carcinomas. As it was expected, this study was predominantly including ground glass nodules. Computed tomography was used to obtain the ratio of consolidation to the maximal tumour diameter to determine invasive potential of the tumours. Overall and disease-free survivals and recurrence-free proportions were analysed. Median age was 64 years. Mean maximal diameter of the tumours was 1.4 ± 0.5 cm. Overall and recurrence-free survivals after limited lung resection were 94.0 and 91.1% at 5 years, respectively. Recurrence-free proportions were 93.7% at 5 years. Unfavourable prognostic factors in overall survival were lymph node metastasis, interstitial pneumonia, male gender, older age, comorbidities (cardiac disease, diabetes etc.) and consolidation/tumour ratio (C/T) ≤ 0.25. C/T ≤ 0.25 predicted good outcomes especially in cT1aN0M0 disease. In a subclass analysis of cT1N0M0 squamous cell carcinomas, wedge resection was the only unfavourable prognostic factor in both overall and disease-free survivals. If the patient was 75 years old or younger and was judged fit for lobectomy, limited resection for cStage I non-small-cell lung cancer (NSCLC) showed excellent outcomes and was not inferior to the reported results of lobectomy for small-sized NSCLC. The carcinomas with C/T ≤ 0.25 rarely recur and are especially good candidates for limited resection.

Regulatory T cells (Tregs) induced by oral tolerance may suppress immunity by production of TGF-β that could also enhance Treg activity. However, all cells that are phenotypically Tregs in rats (CD4⁺CD45RC^high-RC^high) may not have regulatory function. Because Smad7 expression in T cells is associated with inflammation and autoimmunity, then lack of Smad7 may identify those cells that function as Tregs. We reported that feeding type V collagen (col(V)) to WKY rats (RT1^l) induces oral tolerance to lung allografts (F344-RT1^lvl) by T cells that produce TGF-β. The purpose of the current study was to identify the Tregs that mediate col(V)-induced tolerance, and determine Smad7 expression in these cells. RC^high cells from tolerant rats were unresponsive to allogeneic stimulation and abrogated rejection after adoptive transfer. In contrast, CD4⁺CD45RC^low (RC^low) cells from tolerant rats and RC^high or RC^low cells from normal rats or untreated allograft recipients proliferated vigorously in response to donor Ags, and did not suppress rejection after adoptive transfer. TGF-β enhanced proliferation in response to col(V) presented to tolerant RC^high, but not other cells. In contrast to other cells, only RC^high cells from tolerant rats did not express Smad7. Collectively, these data show that the Tregs that mediate col(V)-induced tolerance to lung allografts do not express SMAD7 and, therefore, are permissive to TGF-β-mediated signaling.