MUC1 is expressed at the apical surface of ductal epithelia of tissues, including breast, pancreas, airway, and the gastrointestinal tract, where its functions include lubrication and protection of the epithelia. In addition, roles for MUC1 have been suggested in both adhesive and antiadhesive properties of tumor cells, and extensive O-glycosylation of the MUC1 tandem repeat domain may contribute to these functions. Little information is available on the specific O-glycosylation of MUC1. One problem in identifying different MUC1 glycoforms has been that monoclonal antibodies raised against the MUC1 core protein recognize epitopes in the tandem repeat domain, which is often glycosylated to an extent that obscures these epitopes. We developed an epitope-tagged form of MUC1 that allowed the detection of multiple MUC1 glycoforms and established the presence of a number of important blood group and tumorassociated carbohydrate antigens on MUC1 expressed by two pancreatic tumor cell lines (Panc-1 and S2-013) and two colon tumor cell lines (Caco-2 and HT-29). Antigens detected include sialyl-Lewis a , sialyl-Lewis c , sialyl-Lewis x , and sialyl-Tn.The human epithelial mucin MUC1 (1-4) is a type 1 membrane-bound glycoprotein expressed by ductal epithelia of a number of organs including breast, pancreas, airway, and gastrointestinal tract (reviewed by Gum (5)). Its functions in these tissues include lubrication and protection of the epithelia, and roles in cell adhesion have been suggested (6 -8). There is great diversity in the post-translational processing of MUC1 by epithelial cells in different organs. Moreover, MUC1 is aberrantly expressed by tumors (9) with patterns of post-translational modifications that are different from corresponding normal cell types (10); several different glycoforms of MUC1 were originally described as "tumor-associated antigens." Although MUC1 has been the subject of a number of lines of research, little is known about the mechanisms that direct its diverse post-translational processing.Until recently, there has been little precise information available on the O-glycosylation of MUC1 with respect to blood group antigens. One report demonstrated sLe a 1 and sLe x epitopes on MUC1 core protein expressed in a pancreatic tumor cell line (11), and two reports showed that MUC1 was one of the proteins associated with SLEX antigen secreted by colon carcinoma cells (12,13). In addition, the glycosylation of MUC1 purified from a human mammary tumor cell line (T47D), solid tumor, and human breast milk has been described (14). A major problem in detecting and purifying different glycoforms of the MUC1 core protein is that monoclonal antibodies raised against the core protein bind epitopes in the tandem repeat domain. Many forms of MUC1 that are secreted by different adenocarcinomas are heavily glycosylated in this domain, which obscures the protein epitopes recognized by these anti-MUC1 antibodies. Polyclonal antibodies generated against the cytoplasmic tail (15) do not bind the secreted forms of the...

Mucin glycoproteins play a key role in the normal function of the airway epithelium. We examined the expression of mucin genes, MUC3, 4, 5AC, 5B, 6, 7, and 8 in human fetal tissues to establish the localization and age of onset of expression of each mucin gene during human development. We detected expression of MUC4, 5AC, 5B, and 7 in the mid-trimester airway epithelium but did not detect expression of MUC3, 6, or 8. MUC4 was expressed in the trachea and large airways in the majority of cells in the airway epithelium. Expression of MUC5AC was only seen in individual goblet cells in the trachea, while MUC5B was expressed in the surface epithelium of the trachea at 13 wk but was largely restricted to submucosal glands by 23 wk of gestation.

Box 228, Reading RG6 ZAJ, UK On the basis of enzyme assays, myo-inositol appears to be catabolized via 2-keto-myo-inositol and ~-2,3-diketo-4-deoxy epi-inositol in Rhizobium leguminosarum bv. viciae, as occurs in Klebsiella aerogenes. The first two enzymes of the pathway, myo-inositol dehydrogenase and 2-keto-myo-inositol dehydratase were increased 7-and 77-fold, respectively, after growth of R. leguminosarum on myo-inositol compared to glucose. Cells of R. leguminosarum grown on glucose as the carbon source and then resuspended in myo-inositol, increased myo-inositol-dependent 0, consumption by sixfold in 3 h, confirming this to be an inducible pathway. Succinate, malate and glucose exhibited strong catabolite repression of the myo-inositol catabolic pathway with myo-inositol dehydrogenase and 2-keto-myo-inositol dehydratase being repressed by a t least 68% and 8O%, respectively, in all cases. A dicarboxylate transport mutant (dctA) was unable to repress either enzyme when grown on myo-inositol and succinate. There was no repression of the first two enzymes of the myo-inositol catabolic pathway in the background of constitutive expression of the dicarboxylate transport system, indicating a dicarboxylate must be present to cause repression. The data imply that dicarboxylates are required intra-cellularly to repress these enzymes. Three transposon mutants were isolated that cannot grow on myo-inositol as the sole carbon source and were unable to induce either myo-inositol dehydrogenase or 2-keto-myo-inositol dehydratase. The mutants were unaffected in the ability to nodulate peas and vetch. Furthermore, vetch plants infected with one mutant (RU360) reduced acetylene a t the same rate as plants infected with the wild type. Bacteroids did not oxidize myo-inositol, nor were the catabolic enzymes detected, confirming myo-inositol is not important as an energy source in bacteroids. The possible role of myo-inositol in the rhizosphere is considered.

Aims-A series of patients with myeloma were investigated to assess whether immunological risk factors predisposing to serious infection could be identified. Methods-Patients (n = 102) with predominantly plateau phase myeloma were monitored prospectively for infections. Immunological parameters including total non-paraprotein immunoglobulins and specific antibody titres were measured in all patients and compared with a control population ofhealthy individuals of a similar age; response to immunisation with Pneumovax II, tetanus and diphtheria toxoids and IgG subclasses were measured in a subgroup of 41 patients. Other characteristics investigated for any association with infection included age, sex, paraprotein type, disease stage, and chemotherapy. Results-Specific antibody titres to pneumococcal capsular polysaccharides and tetanus and diphtheria toxoids were significantly reduced compared with the control population. Low antipneumococcal and anti Escherichia coli titres correlated with risk of serious infection and low antipneumococcal titres with severity of nonparaprotein immunosuppression. In 41 immunised patients responses to Pneumovax II, tetanus and diphtheria toxoids were poor; IgG subclass levels were significantly reduced and a poor IgG response to Pneumovax II immunisation was associated with an increased risk of septicaemia and low IgG2 levels. The overall serious infection rate was 0'92 infections per patient year and was four times higher during periods of active disease (1.90) compared with plateau phase myeloma (0.49). The predominant site of infection was the respiratory tract. Clinical and laboratory parameters showed only male sex and reduced non-paraprotein IgG and IgA levels to be significantly associated with at least one serious infection. Conclusions-A subgroup of patients with myeloma with poor IgG responses to exogenous antigens, who are at increased risk of serious infection, can be identified and may benefit from replacement immunoglobulin therapy to reduce the risk of infection. (J Clin Pathol 1995;48:260-266)