Two independent techniques, in situ hybridization on frozen sections and reassociation kinetics, have been used to localize Epstein-Barr virus genomes in tissue samples from healthy human adults. Whereas specimens taken from the palatine tonsils were invariably negative, all samples from the parotid gland were positive when tested with either technique. This observation suggests that the parotid gland is, besides the peripheral lymphocytes, a site of lifelong persistence of Epstein-Barr virus and probably the site of low-level virus production which may be the source of virus found in the oropharynx.

The present morphological study was designed to investigate the expression of HLA class II subregion gene products on human trachea. Frozen sections from the tracheas of 20 cadavers not suffering from ear, nose or throat diseases were studied immunohistochemically using monoclonal antibodies which recognize monomorphic determinants of HLA-DR, -DP and -DQ molecules. Positive reactions could be detected in the airway epithelium and mixed glands. HLA-DR and -DP showed a stronger presence than HLA-DQ. Our results indicate that tracheal mucosa may be the major antigenic structure of the trachea and therefore responsible for the immunogenic action of allogenic tracheal transplants.

It is postulated that class II positive chondrocytes may be actively involved in the destruction or rejection of vital transplanted cartilage grafts. To investigate whether human nasal chondrocytes may also function as accessory cells in ongoing immune reactions with cartilage destruction, mixed leukocyte-chondrocyte cultures and antigen presentation assays were performed. Freshly isolated HLA class II antigen negative chondrocytes obtained from nasal septa were not stimulatory to autologous resting T lymphocytes. HLA class II positive chondrocytes treated with gamma-interferon were able to present antigens to autologous activated T cells derived from an antigen (tetanus) specific T cell line. Upon incubation with activated T cells, initially class II negative changed their phenotype resulting in the expression of class II antigens and enabling them to effectively present antigen. These results suggest an active role of chondrocytes in the rejection of cartilage grafts.

In the field of reconstructive surgery, autologous cartilage grafting is commonly performed to reconstruct skeletal defects. Because of the limited supply of fresh autologous cartilage many investigators concentrate on in vitro production of cartilage tissue. Several growth factors regulate the metabolism and activation of cartilage cells. In order to enhance the culture conditions for cartilage cells, the aim of our investigations was to characterize the influence of transforming growth factor (TGF)-beta, epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) on the proliferation of differentiated human nasal septal chondrocytes. The isolated cells were cultured in monolayer using DMEM with and without 10% FCS. The cell proliferation was assessed using tritiated thymidine. We measured an increase of the proliferation rates when the different growth factors were added. The most important stimulatory effect was due to bFGF and the less to EGF. If all growth factors were added together a fivefold increase in the proliferative activity of the cells was achieved. The effects were further enhanced by factors present in fetal calf serum. We conclude that the culture conditions for cell expansion for cartilage engineering can be optimized employing growth factors.

Reconstructive surgery of multiple areas of the body may require replacement bone or cartilage transplants to repair defects or lesions of skeletal tissue. Advances in cell and tissue culture techniques now permit synthesis of autologous human cartilage in vitro. Several growth factors regulate the metabolism and activation of cartilage cells. To enhance culture conditions and effectiveness for in vitro cartilage engineering, the aim of our investigations was to characterize the influence of transforming growth factor (TGF)-beta and basic fibroblast growth factor (bFGF) on human nasal septal chondrocytes. The isolated cells were cultured as monolayers on plastic and in soft agar. The biological effects of the growth factors were assessed by determining synthesis of total protein and proteoglycan. TGF-beta caused a dose-dependent stimulation of total protein as well as glycosaminoglycan synthesis by all chondrocytes cultured. This stimulatory effect of TGF-beta was greater for chondrocytes cultured in soft agar than for chondrocytes cultured on plastic. No stimulatory effects of matrix synthesis was observed for bFGF in either culture condition. Our results show that TGF-beta can be employed to enhance in vitro production of cartilage grafts for reconstructive surgery.