Wedge-shaped applicator for additional light delivery and dosimetry in the diaphragmal sinus during photodynamic therapy for malignant pleural mesothelioma.

In situ light dosimetry during photodynamic therapy (PDT) of malignant pleural mesothelioma (MPM) after tumour resection facilitates the delivery of a controlled light distribution to the inner thoracic surface. Illumination of the diaphragm-induced sinus, however, remains difficult. Our aim was to develop a wedge-shaped light applicator with incorporated light dosimetry to deliver an additional fluence limited to the sinus. The wedge-shaped applicator contains a cylindrical diffuser for light delivery and two isotropic detectors for simultaneous light dosimetry. These detectors were placed at strategic positions where the fluence rate is maximal or minimal (middle and edge). Prior to its clinical use, the performance of the sinus light applicator was tested in several optical tissue phantoms with different optical properties. The fluence rate distribution over the surface of the applicator showed little change when the wedge was submerged in four different optical phantoms. During clinical PDT of MPM the applicator had to be re-located manually four times in order to give an additional fluence of approximately 2 J cm(-2) to the entire sinus. The light applicator enables dosimetry-controlled light delivery for additional illumination of the sinus region that is often under-illuminated during thoracic integral illumination of MPM.

Involvement of the omental lymphoid organ in the induction of peritoneal immunity against tumor cells.

The omental lymphoid organ (OLO) is a part of the greater omentum composed of vascularized spots containing lymphocytes, plasma cells and macrophages located in a regular pattern between fat cells. To gain insight in the involvement of the OLO in the induction of immunity against tumor cells in the peritoneal cavity, we studied the penetration of tumor cells into the OLO after intraperitoneal, subcutaneous and intravenous injection. Furthermore we analyzed the tumoricidal activity of macrophages isolated from the OLO. Our results indicate that the OLO is only infiltrated by tumor cells directly from the peritoneal cavity, but not by subcutaneously or intravenously injected tumor cells unless they have reached the peritoneal cavity. Bromodeoxy-uridine labelled tumor cells can be detected in the OLO within 10 min after i.p. injection. The penetration is facilitated by the induction of fenestrations between the mesothelial cells (lining the OLO) after intraperitoneal injection of the tumor cells. These fenestrations can also be seen after nonspecific stimulation of the peritoneal cavity. Macrophages isolated from the OLO of mice immunized against syngeneic as well as allogeneic tumor cells express a significant cytotoxicity, which (at least in the syngeneic situation) precedes the cytotoxicity of the macrophages isolated from the peritoneal cavity. In conclusion, our data support the hypothesis that immune reactions against intraperitoneally injected tumor cells are initiated in the OLO leading to 'peritoneal immunity' against these tumor cells.

The thymus in acquired immune deficiency syndrome. Comparison with other types of immunodeficiency diseases, and presence of components of human immunodeficiency virus type 1.

The authors studied thymus specimens taken at autopsy from eight acquired immune deficiency syndrome (AIDS) patients and compared these with those taken from four patients with congenital immunodeficiency (unrelated to an intrinsic thymus defect) and seven patients after allogeneic bone marrow transplantation. In all cases, histology showed a severely involuted architecture, compatible with a debilitating disease before death. There were no major differences between thymus tissue in AIDS patients and in the other patients studied. This argues against the claim expressed in the literature that the epithelial microenvironment incurs particular HIV-1-induced injury in AIDS. This conclusion is substantiated by immunohistochemistry for HIV-1 gag and env proteins, and by hybridohistochemistry for gag/pol and env mRNA of HIV-1. Positive cells were observed only in low numbers, both inside the epithelial parenchyma and in the (expanded) perivascular areas. An interesting finding was the labeling of subcapsular/medullary epithelium in normal uninvoluted thymus by a number of antibodies to HIV-1 gag p17 and p24 proteins. Compatible with this labeling was the staining of epithelial stalks in hyperinvoluted thymuses irrespective of disease category. The previously reported cross-reactivity between HIV-1 core protein and thymosin alpha 1 cannot fully explain this observation, because the epithelium in the hyperinvoluted state is negative for thymosin alpha 1. This study confirms and extends previous reports on the endogenous presence of epitopes of retroviral antigens in thymic epithelium.