Synergistic interaction of two independent genetic loci causes extreme elevation of serum IgA in mice.

Understanding the molecular regulation of immunoglobulin A (IgA) expression is important as it plays an essential role in the first-line defence through mucosal secretions. Using inbred mouse strains, we identified two independent and dominant acting genetic loci that synergistically cause a 40-fold upregulation in serum IgA levels when introduced into the murine strain C57Bl/6J (B6). The first locus on chromosome 12 appears to be mainly responsible for the natural four-fold higher IgA levels in C3HeB/FeJ (C3H) compared to B6 mice. A second independent, chemically induced mutation on chromosome 5 caused a two-fold elevation when transferred from C3H into B6 mice. Both loci in concert effect a 40-fold elevation against the B6 genetic background. We determined the chromosomal localization of the two loci simultaneously by a one-step mapping process. The chemically induced mutation was identified within the immunoglobulin joining chain (IgJ) gene on chromosome 5. The major serum IgA modifier between the C3H and B6 was located on chromosome 12. This modifier region was mapped to a 350 kb region containing several immunoglobulin heavy-chain genes and the Ig alpha germline switch gene. We speculate that by interfering with both IgA expression and distribution, synergistic regulation of IgA is achieved.

Ultrastructural co-localization of TFF3-peptide and oxytocin in the neural lobe of the porcine pituitary.

TFF-peptides (formerly P-domain peptides, trefoil factors) are typical secretory products of many mucous epithelial cells. TFF3 is also synthesized in oxytocinergic neurons in the paraventricular and supraoptic nuclei of the human hypothalamus. Here, TFF3 and oxytocin are shown to be co-localized within the same secretory vesicles in the neural (posterior) lobe of the procine pituitary by means of immunoelectron microscopy. Relatively large amounts of TFF3, but not TFF1 and TFF2, are present in the neural lobe of the porcine pituitary, where it is probably released into the bloodstream.

Molecular medicine of TFF-peptides: from gut to brain.

TFF-peptides (i.e. TFF1, TFF2, TFF3; formerly P-domain peptides, trefoil factors) have been established as secretory products typical of the gastrointestinal tract. Their synthesis has recently been recognized in a number of mucin-producing epithelial cells, for example, of the respiratory tract, the salivary glands, the uterus and of the conjunctiva. They have a pivotal role in maintaining the surface integrity of these delicate epithelia as constituents of mucus gels as well as by their anti-apoptotic properties and their motogenic activity modulating cell migratory processes. The latter is important for rapid healing in particular of gastrointestinal and respiratory epithelia by a process termed "restitution". On the other hand, one of these peptides--namely TFF3--has been detected as a new neuropeptide of the human hypothalamo-pituitary axis where it is synthesized in oxytocinergic neurons of the paraventricular and supraoptic nuclei. From there it is transported to the posterior pituitary where it is released into the blood stream. Synthesis of TFF-peptides also occurs pathologically as result to chronic inflammatory diseases, for example of the gastrointestinal tract. Aberrant synthesis of TFF-peptides is observed in many tumors.

Co-localization of TFF3 peptide and oxytocin in the human hypothalamus.

TFF-peptides (formerly P domain peptides, trefoil factors) are typical secretory products of many mucous epithelial cells. TFF3 is also synthesized in the hypothalamus and has anxiolytic or anxiogenic activities when injected into the rat amygdala. Here we show by immunohistochemistry that TFF3 is localized to a distinct population of neurons of the human hypothalamic paraventricular and supraoptic nuclei. Generally, TFF3-positive cells are co-localized in oxytocin-producing cells and not in vasopressin-producing cells. Relatively large amounts of TFF3-but not TFF1 and TFF2-are present in the posterior lobe of the human pituitary, where it is probably released into the bloodstream. Furthermore, TFF3 was also detectable in human postmortem cerebrospinal fluid.

Secretion of TFF-peptides by human salivary glands.

TFF-peptides (formerly P-domain peptides, trefoil factors) are typical secretory products of mucin-producing cells and seem to influence the rheological properties of mucous gels. Here, localization studies of TFF-peptides in human salivary glands are presented. Expression studies (polymerase chain reaction) revealed mainly TFF3 transcripts in submandibular and sublingual glands and trace amounts in parotid glands. Only low levels of expression of TFF1 could be monitored in submandibular and sublingual glands, and TFF2 transcripts were hardly detectable in all three major salivary glands. This result was partly confirmed by Western blot analysis, which only detected TFF3 in submandibular glands, but not in sublingual and parotid glands. TFF3 was also shown to be a constituent of human saliva. Immunofluorescence localized TFF3 solely in the secretory granules of serous cells of submandibular glands but not in mucous cells. This localization is remarkably similar to that of the unique low-molecular-weight mucin MUC7, which interacts with a number of oral microorganisms.

Secretory peptides TFF1 and TFF3 synthesized in human conjunctival goblet cells.

PURPOSE: The objective of this study was to determine whether human conjunctival epithelium synthesizes TFF-peptides (formerly P-domain peptides, trefoil factors), a family of mucin-associated secretory peptides of the gastrointestinal tract. METHODS: Expression of TFF-peptides in human conjunctiva was monitored by reverse transcription-polymerase chain reaction analysis. Antisera specific for TFF-peptides were used for immunohistochemistry to determine the presence and distribution of TFF-peptides in human conjunctiva. RESULTS: mRNA expression of TFF1 and TFF3, but not TFF2, was detected in human conjunctiva. TFF1 and TFF3 but not TFF2 are stored in conjunctival goblet cells only as revealed by immunofluorescence. CONCLUSIONS: Goblet cells of the human conjunctiva synthesize TFF1 and TFF3. These peptides, together with the secretory ocular mucin MUC5AC, may contribute to the rheological properties of the tear film. They also may influence healing of corneal wounds due to their motogenic properties.

Localization of TFF3 peptide to porcine conjunctival goblet cells.

TFF-peptides (formerly P-domain peptides, trefoil factors) form a new family of mucin-associated peptides mainly in the gastrointestinal tract. TFF3 is a typical secretory product of intestinal goblet cells and occurs also in the respiratory tract. Here, polyclonal antisera specific for TFF3 were used in Western blot analysis and immunofluorescence to determine the presence and distribution of TFF3 in the porcine conjunctiva, which is the primary source for ocular mucins. Significant accumulation of TFF3 was detected in conjunctival goblet cells but not in the lacrimal glands. This peptide, together with ocular mucins, may play a role in the rheological function of the tear film.

Localization of TFF3, a new mucus-associated peptide of the human respiratory tract.

Trefoil factor family (TFF)-domain peptides (formerly P-domain peptides, trefoil factors) represent major mucin-associated peptides of the gastrointestinal tract. Here, the first localization studies on TFF3 in the lower respiratory tract of human material are presented. Immunohistochemistry revealed significant accumulation of TFF3 to mucous cells in the acini of submucosal glands and varying amounts in goblet cells at the ductular portions and the surface epithelium. TFF3 appears also as a component of the mucus, for example from patients with chronic bronchitis. Expression of TFF3 was also shown by use of the polymerase chain reaction. In contrast, TFF1 and TFF2 transcripts were hardly detectable in the human respiratory tract. Thus, a structural function of TFF3 for the airway mucus is discussed, possibly together with the mucins MUC5B and MUC5AC.

Differential expression of the TFF-peptides xP1 and xP4 in the gastrointestinal tract of Xenopus laevis.

TFF-peptides (formerly P-domain peptides, trefoil factors) represent major secretory products of the mammalian gastrointestinal tract. A molecular cloning approach revealed the existence of two TFF-peptides, xP1 and xP4, also in the stomach of Xenopus laevis. Here, the localization of these two peptides by Western blot analysis as well as immunohistochemistry is presented. xP1 is found predominantly in the surface mucous cells of the stomach, whereas xP4 is mainly localized to a specific population of goblet cells in the esophagus, to mucous neck cells of the stomach, and to closely resembling cells in antral glands. xP4 in the esophagus and in the stomach differ by their N-glycosylation patterns. Compared to mammalian TFF-peptides, xP1 obviously represents the frog homologue of human TFF1 (formerly pS2) and xP4 seems to be the amphibian equivalent of human TFF2 (formerly hSP).