R Shirakura

Preoperative left ventricular function: minimal requirement for successful late results of valve replacement for aortic regurgitation

Postoperative survival and left ventricular function were studied in 62 patients who underwent aortic valve replacement for isolated, chronic aortic regurgitation between 1978 and 1985. The average follow-up period was 3.8 years. There were three in-hospital and six late deaths. Five (56%) of the nine postoperative deaths were of cardiac-related causes. The mean 7 year survival rate was 83 +/- 5%. Preoperative left ventricular end-systolic volume index was the most important indicator (p less than 0.001) for subsequent cardiac death. The 6.5 year survival rate was 92 +/- 4% for patients with an end-systolic volume index less than 200 ml/m2 compared with 51 +/- 16% for those whose index was greater than 200 ml/m2. None of the 48 patients with an end-systolic volume index less than 200 ml/m2 died of cardiac-related causes. Twenty-three of the 48 patients with an end-systolic volume index less than 200 ml/m2 (Group 1) and 6 of the 12 patients with a higher index (Group 2) underwent repeat catheterization 26 months postoperatively. Preoperative afterload, assessed by end-systolic wall stress, was elevated in both groups, but decreased postoperatively, becoming identical to the afterload in 20 normal control subjects. Although the preoperative ejection fraction was depressed in both groups, the great majority of patients in Group 1, compared with none in Group 2, exhibited normal ejection fraction postoperatively. Thus, in patients who recently underwent surgery for aortic regurgitation, satisfactory late results in both long-term survival and reversal of left ventricular dysfunction were obtained when the preoperative end-systolic volume index was less than 200 ml/m2.

Prolonging discordant xenograft survival with anticomplement reagents K76COOH and FUT175.

The guinea pig heart, when transplanted into the rat heterotopically, is rejected within 30 min via activation of the alternative complement pathway. Natural antibody does not contribute to rejection. This xenotransplantation model was used to assess the effect of anti-complement reagents on discordant xenograft survival. In vivo administration of K76COOH (K76) to rats induced only slight suppression of factors B and D and a marked decrease of C3, leading to the depression of ACH50 (reflecting the potency of the alternative pathway). On the other hand, FUT175 (FUT) reduced C3 activity by about 80% and inhibited factor B activity nearly 100% < 1 hr after the administration, but inhibited factor D activity only marginally. FUT abrogated ACH50 for > 6 hr. Of note, the xenograft beating time was prolonged approximately 3 times by FUT but not by K76, suggesting that direct inhibition of plasma serine protease factor B results in the complete suppression of ACH50 and graft survival. The administration of both K76 and FUT resulted in the longest graft survival, but the effects of these reagents were abolished by additional antigraft antibody. Anticomplement reagents that block factor B and C3 are therefore effective for prolongation of discordant xenograft survival when the graft rejection is associated with the complement alternative pathway.

Altered T cell development in human thymoma is related to impairment of MHC class II transactivator expression induced by interferon-gamma (IFN-γ)

Thymoma is known to contain CD4+CD8+ T cells, indicating that neoplastic epithelial cells of thymoma have a function as thymic cortical epithelium. However, it has been shown that there is an impairment of CD4+ T cell development in thymoma and that IFN‐γ‐induced HLA‐DR expression on cultured thymic epithelial cells (TEC) derived from thymoma is decreased when compared with the normal thymus. MHC class II transactivator (CIITA) is known to play a critical role in IFN‐γ‐induced MHC II expression. In this study, we attempted to elucidate whether CIITA is responsible for the impaired up‐regulation of MHC II molecules in response to IFN‐γ in thymoma TEC. A quantitative reverse transriptase‐polymerase chain reaction examination revealed that the induced level of CIITA was significantly lower in thymoma TEC than in normal TEC. The induced levels of invariant chain (Ii) and HLA‐DR in thymoma TEC were correlated with CIITA expression. The proportion of CD3+ cells in the CD4+CD8− subset in thymoma was also correlated with CIITA expression. A gel mobility shift assay however, revealed translocation of STAT1 to the nucleus in thymoma as well as normal TEC. Intercellular adhesion molecule‐1 was up‐regulated in the thymoma TEC to a level similar to normal TEC in response to IFN‐γ. These results indicate that impaired up‐regulation of HLA‐DR in response to IFN‐γ results from insufficient induction of CIITA, but not from the signal from IFN‐γ receptor to the nucleus. The abnormal regulation of HLA‐DR expression caused by impaired induction of CIITA may affect CD4+ T cell development in thymoma.

The possible use of HLA-G1 and G3 in the inhibition of NK cell-mediated swine endothelial cell lysis

The splicing isoform of HLA‐G that is expressed in xenogeneic cells, and its effect on NK‐mediated direct cytotoxicity was examined, using stable Chinese hamster ovary (CHO) cell or swine endothelial cell (SEC) transfectants. cDNAs of HLA‐G (G1 and G3) and human β2‐microglobulin were prepared and subcloned into the expression vector, pCXN. The transfected HLA‐G1 was easily expressed on SEC, and co‐transfection with human β2‐microglobulin led to an enhanced level of HLA‐G1 expression, as evidenced by flow cytometry. The expressed HLA‐G1 significantly suppressed NK‐mediated SEC cell lysis, which is an in vitro delayed‐type rejection model of a xenograft. On the other hand, the swine leucocyte antigen (SLA) class I molecules could be up‐regulated as the result of the transfection of human β2‐microglobulin, but did not down‐regulate human NK‐mediated SEC lysis. The HLA‐G3 was not expressed on CHO and SEC in contrast to HLA‐G1, as the result of the transfection. The gene introduction of HLA‐G3 in SEC showed no protective effect from human NK cells. However, indirect evidence demonstrated that HLA‐G3 transfection resulted in HLA‐E expression, but not itself, when transfected to the human cell line, 721.221, thus providing some insight into its natural function in human cells. The present findings suggest that the expression of HLA‐G1 on the cell surface could serve as a new approach to overcoming NK‐mediated immunity to xenografts.

Long-term results of direct-current cardioversion after open commissurotomy for mitral stenosis

For a 7-year period, cardiac rhythm before and after surgery was determined in 106 patients with mitral stenosis presenting with atrial fibrillation (AF) who had undergone open mitral commissurotomy. Forty-three of the patients reverted to sinus rhythm (SR) after primary or secondary direct-current (DC) cardioversion after surgery and maintained it until discharge from hospital. Thirty patients maintained SR for 3 months to 7.2 years (mean 2.5 years) after surgery. The actuarial maintenance rate of SR was 50% 7 years after surgery in these 43 patients. The duration of AF, preoperative left atrial dimension by M-mode echocardiogram and pathologic classification of the mitral valve were factors supposedly influencing the maintenance of SR for a long period after DC cardioversion. In 30 patients who reverted back to SR and maintained SR late postoperatively, the preoperative duration of AF was up to 5 years, and 35% of the patients had had AF for more than 1 year. Also, in 40% of these 30 patients, the preoperative cardiothoracic ratio was more than 60%. It is concluded that if sinus rhythm is restored by DC cardioversion before discharge from hospital after open mitral commissurotomy, it has a 50% chance of being maintained for 7 years after surgery. Long duration of AF and large cardiothoracic ratio should probably not dissuade one from attempting secondary DC cardioversion in these patients.

Impaired expression of MHC class II molecules in response to interferon-gamma (IFN-γ) on human thymoma neoplastic epithelial cells

A human thymoma is a neoplasm derived from the thymic epithelial cell, and is well known for its association with autoimmune diseases, especially myasthenia gravis. The neoplastic epithelial cells of thymoma clearly retain thymic epithelial functions, but the development of T cells in thymoma is somewhat impaired. In this study, we quantified by flow cytometry the in vitro expression of MHC molecules on neoplastic epithelial cells precultured with IFN‐γ. While MHC class I expression was comparable with that on normal thymic epithelial cells, the level of MHC class II molecules on neoplastic epithelial cells was lower than in controls, and also varied greatly from case to case. Additionally, there was a significant positive correlation between the expression level of MHC class II and the proportion of mature CD3+ cells in the CD4+CD8− subset. Thus, accumulation of CD3−CD4+CD8− cells in thymoma may result from impaired expression of the MHC class II molecules, suggesting that the function of the neoplastic epithelial cells might determine the maturation and the positively selected repertoire of T cells in thymomas.

Increased nitric oxide levels in exhaled air of rat lung allografts

In organ transplantation nitric oxide has been reported to be involved in allograft rejection. We examined in a rat lung transplantation model whether nitric oxide is overproduced in acute rejection and can be detected in exhaled air. Thirteen rat right lung transplants were separated into three groups: group 1 (n = 5), untreated allografts (Brown-Norway [RT1n] to Lewis [RT1l]); group 2 (n = 4), cyclosporine-treated allografts; and group 3 (n = 4), isografts (Lewis to Lewis). We examined exhaled nitric oxide levels with a chemiluminescence analyzer and chest roentgenograms on days 2 through 5. Histologic samples were obtained on days 3 and 5. On day 5, the recipients were killed and we measured exhaled nitric oxide from the right and left lungs separately. Blood samples were also obtained for measurement of serum nitrite/nitrate. The exhaled nitric oxide level in untreated allografts increased significantly from day 5 (63.9 +/- 39.2 ppb, p = 0.0095) and was significantly higher than that in treated allografts (9.1 +/- 1.6 ppb) (p = 0.0085) and isografts (6.9 +/- 0.5 ppb) (p = 0.0068). The nitric oxide level in untreated allografts (826.5 +/- 416.1 ppb) was 75 times as high as that from the contralateral normal left lungs (11.2 +/- 2.6 ppb) (p = 0.0118). The level of exhaled nitric oxide correlated significantly with the histologic rejection grade (p = 0.0001). There was no significant difference in the serum nitrite/nitrate levels between allografts and isografts. These data suggest that increased exhaled nitric oxide levels might reflect acute rejection in lung transplants.

C5b-8 Step Lysis of Swine Endothelial Cells by Human Complement and Functional Feature of Transfected CD59

The authors established several swine endothelial cell (SEC) lines expressing human CD59 by transfection of cDNA, and assessed the function of the transfectant molecules in comparison with those of membrane cofactor protein (MCP) and decay‐accelerating factor (DAF) in an in vitro hyperacute rejection model of swine to human discordant xenograft. At the usual expression rate, DAF and MCP protected SEC from human complement mediated cell lysis, but CD59 did not block human complement attack on SEC. However, CD59 protects SEC from cell lysis when sufficiently expressed as in human umbilical vein (HUVEC). The authors examined why CD59 needed so many molecules to protect human complement‐mediated SEC lysis and found that SEC underwent lysis by human C5b‐8. The degree of C5b‐8 step lysis of SEC was approximately 70% of the total activity (C5b‐9). Additionally, CD59 protected human complement activation less efficiently at the C5b‐8 step than at the C9‐step. Therefore, to overcome human complement mediated SEC lysis, C8 activity must be inhibited by dense expression of CD59.

A surface-bound form of human C1 esterase inhibitor on xenografts: the complement regulatory function.

THE PURPOSE of the present study was to investigate the effect of the C1 esterase inhibitor (C1-INH), on a swine endothelial cell (SEC) membrane against human complement attack. Human C1-INH functions as an inhibitor for the complement reaction at the first step of the classical pathway in the fluid phase. The basic function of the transfected molecules on the xenosurface was investigated using Chinese hamster ovary (CHO) transfectants for the sake of convenience. The efficacy of C1-INH-mediated protection of SEC from human complement was then assessed as an in vitro hyperacute rejection model of a swine to human discordant xenograft.

Analysis of the elephant trunk method in patients with extensive thoracic aortic aneurysm

We assessed the appropriate length of an elephant trunk prosthesis based on our experience with 9 patients experiencing extensive thoracic aneurysms. There were 3 patients with a true aneurysm, 5 patients with a dissecting aortic aneurysm, and 1 patient with a true plus dissecting aortic aneurysm. The subjects were 4 men and 5 women and, at the time of operation, were from 38 to 74 years old. The second-stage operations were performed on 6 patients from 9 days to 6 months after the first-stage operation. In the first-stage operation, one patient died of pneumonia during the hospital stay and another died of multi-organ infarction after 15 months. In the second-stage operation, two patients died of brain hemorrhage in the chronic stage after the operation. The length of the elephant trunk prosthesis was 3 cm in the three early patients, and in one of them the elephant trunk could not be utilized due to its insufficient length. In the next three patients, the length was extended to 5 cm, but one of patient experienced an expansion of the aneurysm in the descending aorta due to a graft of insufficient length which could not decompress the aneurysmal wall. Therefore, in the last three patients, the length was further extended to 10 cm, and the second-stage operation was performed uneventfully on the 64th, 9th and 45th day, respectively after the first-stage operation within a continuous hospital stay. Neither expansion of the aneurysm nor thromboembolism was found during the waiting period for any of the second-stage operations. Accordingly, we recommend using a 10 cm elephant trunk prosthesis.