Expression of the a1-proteinase inhibitor (a1PI) gene was studied in human mononuclear cells. Using RNA blot and dot hybridization, a1PI mRNA was detected in human peripheral blood monocytes, bronchoalveolar and breast milk macrophages, but not in B or T lymphocytes. Using incorporation of a radiolabeled amino acid precursor, synthesis and secretion of a1PI were demonstrated in human monocytes and macrophages, but not in lymphocytes. In addition, a1PI was secreted in functionally active form as shown by complexing with serine proteases. Biosynthesis of a1PI by mononuclear phagocytes was greatest during the first 24 hr in culture and progressively decreased over the next 10 days. The reduction in a1PI biosynthesis in vitro involved a mechanism acting at the pretranslational level as a1PI mRNA content also progressively declined over 10 days in culture. The ease of sampling human monocytes and macrophages now permits examination of the biochemical defect in homozygous PiZ and PiS a1PI deficiencies and study of the functional significance of locally produced aIPI in normal tissues and sites of injury or inflammation.a1-proteinase inhibitor (a1PI), a single-chain 55-kDa glycoprotein, is a major serine proteinase inhibitor in human plasma. It is characterized by a remarkable degree of polymorphic variition. Two of the variants, PiZ a1PI and PiS a1PI, are associated with moderately to severely diminished plasma levels and, in many cases, the development of chronic disease in liver and/or lung (1-3).Although it is generally considered a tissue-specific product of the liver, several recent studies have suggested that a1PI is also produced by human mononuclear cells (4-8).Other plasma proteins, including many of the complement proteins, a-2-macroglobulin, lysozyme, and plasminogen activator, that are predominantly synthesized by the liver are also synthesized by monocytes and macrophages, and the products are thought to have important functions in regulation of local tissue injury (9-13). Unfortunately, technical limitations in separation of mononuclear cell subpopulations, biosynthetic labeling, and analytical methods in previous reports (4-8) have prevented definitive identification of a1PI biosynthesis in human mononuclear cells. In the present study, we provide evidence for transcription of the aPI gene and translation, postsynthetic processing, and secretion of a1PI in a functionally active form in human peripheral blood monocytes, bronchoalveolar and breast milk macrophages, but not in B or T lymphocytes. MATERIALSDulbecco's modified Eagle's medium (DME medium), DME medium lacking methionine, RPMI 1640 medium, RPMI 1640 lacking methionine, Hanks' balanced salt solution, and fetal bovine serum were purchased from GIBCO and medium 199 was from M. A. Bioproducts (Walkersville, MD).[35S]Methionine (specific radioactivity, -1000 Ci/mmol; 1 Ci = 37 GBq) and [32P]deoxycytidine triphosphate (specific radioactivity, =3000 Ci/mmol) were obtained from New England Nuclear and 14C-methylated protein standards were from ...

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Genetic deficiency of the second component of complement (C2) is the most common complement-deficiency state among Western Europeans and is frequently associated with autoimmune diseases. To examine the molecular basis of this deficiency, we established cultures of blood monocytes from four families with C2-deficient members. Using a hemolytic-plaque assay, [35S]methionine metabolic labeling of proteins in tissue culture and immunoprecipitation, RNA extraction and Northern blot analysis, and DNA restriction-enzyme digestion and Southern blot analysis, we found that C2 deficiency is not due to a major gene deletion or rearrangement but is the result of a specific and selective pretranslational regulatory defect in C2 gene expression. This leads to a lack of detectable C2 mRNA and a lack of synthesis of C2 protein. The approach used in this study should prove useful in examination of other plasma protein deficiencies, especially those in which the deficient gene is normally expressed in peripheral-blood monocytes or tissue macrophages and in which ethical considerations preclude the use of liver or other tissue for study.

From 1980-1986 intestinal mucosal lymphangiectasia was diagnosed histologically in eight patients (6 weeks to 16 years; four males/four females; seven white). The presenting features were diarrhea (six/eight), vomiting (four/eight), and growth deficit (seven/eight). Additional conditions in these patients included asthma, urinary tract infection, esophageal atresia, hydrops fetalis, inflammatory bowel disease, malabsorption syndrome, and thymic hypoplasia. Hypoalbuminemia and edema (four/eight) were more prominent in those patients under 5 years of age. Two had systemic lymphangiectasia and lymphopenia. The patients responded variably to hyperalimentation and dietary supplements, depending on the extent of their lymphangiectasia and the age at onset of symptoms. Dilated lymphatics were seen in the small intestinal mucosa under the surface epithelium. Lesions were often focal, requiring several biopsies or serial sections for detection. Other common findings were mild to moderate lymphoplasmacytic inflammation and mild to moderate villous injury with blunting and edema. Mild inflammation without lymphangiectasia was also present in esophageal, gastric, or colonic biopsies. Diagnosis should be made on the basis of endoscopic findings or in small-intestinal inflammatory conditions even in the absence of a classic clinical picture. Histologic confirmation may require more than one serially sectioned biopsy. This study confirms the diversity of disorders that may be associated with intestinal lymphangiectasia and shows that the disease in infants is more severe and generalized.