Gendler, Sandra

In gene-targeted mouse models for cystic fibrosis (CF), the disease is mainly manifested by mucus obstruction in the intestine. To explore the mucus composition, mucins insoluble and soluble in 6M guanidinium chloride were purified by three rounds of isopycnic ultracentrifugation from the small and large intestines of CF mice (Cftrm1UNC/Cftrm1UNC) and compared with wild-type mice. The amino acid composition was typical of that for mucins and showed increased amounts of the insoluble (2.5-fold increase) and soluble (7-fold increase) mucins in the small intestine of the CF mice compared with wild-type mice. Mucins from the large intestine of both wild-type and CF mice showed a high but constant level of fucosylation. In contrast, the insoluble and soluble mucins of the small intestine in CF mice revealed a large increase in fucose, whereas those of wild-type mice contained only small amounts of fucose. This increased fucosylation was analysed by releasing the O-linked oligosaccharides followed by GC-MS. NMR spectroscopy revealed that the increased fucosylation was due to an increased expression of blood group H epitopes (Fucα1-2Gal-). Northern-blot analysis, using a probe for the murine Fucα1-2 fucosyltransferase (Fut2), showed an up-regulation of this mRNA in the small intestine of the CF mice, suggesting that this enzyme is responsible for the observed increase in blood group H-type glycosylation. The reason for this up-regulation could be a direct or indirect effect of a non-functional CF transmembrane conductance regulator (CFTR) caused by the absence of CFTR channel.

Immunological unresponsiveness established by the elimination or anergy of self-reactive lymphocyte clones is of importance to immunization against tumor-associated antigens. In this study, we have investigated induction of immunity against the human MUC1 carcinoma-associated antigen in MUC1 transgenic mice unresponsive to MUC1 antigen. Immunization of adult MUC1 transgenic mice with irradiated MUC1-positive tumor cells was unsuccessful in reversing unresponsiveness to MUC1. By contrast, fusions of dendritic cells with MUC1-positive tumor cells induced cellular and humoral immunity against MUC1. Immunization with the dendritic cell fusions that express MUC1 resulted in the rejection of established metastases and no apparent autoimmunity against normal tissues. These findings demonstrate that unresponsiveness to the MUC1 tumor-associated antigen is reversible by immunization with heterokaryons of dendritic cells and MUC1-positive carcinoma cells.