The binding of human milk lactoferrin to immunoglobulin A

Conjugated Nonionic Detergent Micelles: An Efficient Purification Platform for Dimeric Human Immunoglobulin A

The SARS-COV-2 virus is a deadly agent of inflammatory respiratory disease. Since 2020, studies have focused on developing new therapies based on galactose-rich IgA antibodies. Clinical surveys have also revealed that galactose-deficient IgA1 polymerizes in serum, producing IgA nephropathy, which is a common cause of kidney failure in young adults. Here we show that IgA1-IgA2 dimers are efficiently and economically purified in solution via conjugated nonionic surfactant micellar aggregates. Quantitative capture at pH 7 and extraction at pH 6.5 can avoid antibody exposure to acidic, potentially denaturing conditions. Brij-O20 aggregates lead to the highest process yields (88-91%) and purity (94%). Recovered IgA dimers preserve their native secondary structure and do not self-associate. Increasing the reaction volume has little impact on yield or purity. By introducing an efficient, inexpensive IgA purification protocol, we assist pharmaceutical firms and research laboratories in developing new IgA-based therapies as well as in increasing our understanding of IgA1 polymerization.

The acute phase protein lactoferrin is a key feature of Alzheimer's disease and predictor of Aβ burden through induction of APP amyloidogenic processing

Amyloidogenic processing of the amyloid precursor protein (APP) forms the amyloid-β peptide (Aβ) component of pathognomonic extracellular plaques of AD. Additional early cortical changes in AD include neuroinflammation and elevated iron levels. Activation of the innate immune system in the brain is a neuroprotective response to infection; however, persistent neuroinflammation is linked to AD neuropathology by uncertain mechanisms. Non-parametric machine learning analysis on transcriptomic data from a large neuropathologically characterised patient cohort revealed the acute phase protein lactoferrin (Lf) as the key predictor of amyloid pathology. In vitro studies showed that an interaction between APP and the iron-bound form of Lf secreted from activated microglia diverted neuronal APP endocytosis from the canonical clathrin-dependent pathway to one requiring ADP ribosylation factor 6 trafficking. By rerouting APP recycling to the Rab11-positive compartment for amyloidogenic processing, Lf dramatically increased neuronal Aβ production. Lf emerges as a novel pharmacological target for AD that not only modulates APP processing but provides a link between Aβ production, neuroinflammation and iron dysregulation.

Advances in lactoferrin research concerning bovine mastitis

Lactoferrin is a multifunctional, iron-binding glycoprotein found in milk and other exocrine secretions. Lactoferrin in milk plays vital roles in the healthy development of newborn mammals, and is also an innate resistance factor involved in the prevention of mammary gland infection by microorganisms. Inflammation of the udder because of bacterial infection is referred to as mastitis. There have been many investigations into the relationships between lactoferrin and mastitis, which fall into several categories. The main categories are fluctuations in the lactoferrin concentration of milk, lactoferrin activity against mastitis pathogens, elucidation of the processes underlying the onset of mastitis, participation of lactoferrin in the immune system, and utilization of lactoferrin in mastitis treatment and prevention. This minireview describes lactoferrin research concerning bovine mastitis. In the 1970s, many researchers reported that the lactoferrin concentration fluctuates in milk from cows with mastitis. From the late 1980s, many studies clarified the infection-defense mechanism in the udder and the contribution of lactoferrin to the immune system. After the year 2000, the processes underlying the onset of mastitis were elucidated in vivo and in vitro, and lactoferrin was applied for the treatment and prevention of mastitis.

The unexplored roles of human serum IgA

The roles of human serum IgA, in contrast to that of mucosal IgA, are relatively unexplored. Previous studies have shown that IgA mediates either pro- or anti-inflammatory effects in innate immune cells. Serum IgA has been shown to interact with many proteins and glycoproteins of which the functions and mechanisms are not fully characterized. Here, we present fresh perspectives into the roles of serum IgA, describing novel IgA-protein interactions, the importance of its glycosylation status in normal functions, and the plausible role of IgA as a driver and regulator of autoimmune diseases/immune overactivation. Other potential roles, including the regulation of cytokines, effector cell function, and homeostasis, are considered in view of the maintenance of immune function. We anticipate future research to uncover new anti-inflammatory or pro-inflammatory roles of human serum IgA in immune functions and dysfunctions, with implications on systemic lupus erythematosus (SLE).

DNA, oligosaccharides, and mononucleotides stimulate oligomerization of human lactoferrin

Using small-angle X-ray scattering (SAXS), light scattering (LS), and soft laser ablation we have shown that lactoferrin (LF) in solution at neutral pH is oligomerized in the absence of salt or at physiological salt concentrations. The level of oligomerization depends on the concentration of LF, KCl or NaCl, and on the duration of the protein storage in solution. At the concentrations comparable with those in human milk (1-6 mg/ml), the average radius of gyration (R(g)) values of LF can attain 400-480 A, while fresh solution of previously lyophylized LF demonstrate a lower average R(g) (50-100 A), and R(g) value characterizing the LF monomer formed at 1 M NaCl is 26.7 A. The addition of oligonucleotides, oligosaccharides, or mononucleotides to LF in the presence or in the absence of KCl with different level of initial oligomerization accelerates the oligomerization rate and increases the R(g) values up to approximately 600-700 A, which correspond to associates containing ten or more protein molecules. During gel filtration on Sepharose 4B, high-degree LF oligomers dissociate nearly completely forming different degraded complexes, but in some cases it is possible to reveal small amount of a decamer. A possible role for oligomerization of LF, a highly polyfunctional protein, for its different biological activities is discussed.

Effect of lactoferrin on oxidative features of ceruloplasmin

In our previous report we first described a complex between lactoferrin (Lf) and ceruloplasmin (Cp) with K (d) approximately 1.8 microM. The presence of this complex in colostrum that never contains more than 0.3 microM Cp questions the reliability of K (d) value. We carefully studied Lf binding to Cp and investigated the enzymatic activity of the latter in the presence of Lf, which allowed obtaining a new value for K (d) of Cp-Lf complex. Lf interacting with Cp changes its oxidizing activity with various substrates, such as Fe(2+), o-dianisidine (o-DA), p-phenylenediamine (p-PD) and dihydroxyphenylalanine (DOPA). The presence of at least two binding sites for Lf in Cp molecule is deduced from comparison of substrates' oxidation kinetics with and without Lf. When Lf binds to the first site affinity of Cp to Fe(2+) and to o-DA increases, but it decreases towards DOPA and remains unchanged towards p-PD. Oxidation rate of Fe(2+) grows, while that of o-DA, p-PD and DOPA goes down. Subsequent Lf binding to the second center has no effect on iron oxidation, hampers DOPA and o-DA oxidation, and reduces affinity towards p-PD. Scatchard plot for Lf sorbing to Cp-Sepharose allowed estimating K (d) for Lf binding to high-affinity (approximately 13.4 nM) and low-affinity (approximately 211 nM) sites. The observed effect of Lf on ferroxidase activity of Cp is likely to have physiological implications.

Structural Characterization of the Ceruloplasmin: Lactoferrin Complex in Solution

Ceruloplasmin is a copper protein found in vertebrate plasma, which belongs to the family of multicopper oxidases. Like transferrin of the blood plasma, lactoferrin, the iron-containing protein of human milk, saliva, tears, seminal plasma and of neutrophilic leukocytes tightly binds two ferric ions. Human lactoferrin and ceruloplasmin have been previously shown to interact both in vivo and in vitro forming a complex. Here we describe a study of the conformation of the human lactoferrin/ceruloplasmin complex in solution using small angle X-ray scattering. Our ab initio structural analysis shows that the complex has a 1:1 stoichiometry and suggests that complex formation occurs without major conformational rearrangements of either protein. Rigid-body modeling of the mutual arrangement of proteins in the complex essentially yields two families of solutions. Final discrimination is possible when integrating in the modeling process extra information translating into structural constraints on the interaction between the two partners.

Biological Functions of IgA

Immunoglobulin A (IgA) is the most enigmatic of immunoglobulins. It is by far the most abundant of human Igs, being present in the blood plasma at concentrations approximating 2–3mg/mL, as well as the dominant isotype in most secretions where its output amounts to some 5–8g/day in adults. Furthermore, its evolutionary origins appear to precede the synapsid– diapsid divergence in tetrapod phylogeny (>300 million years ago) because it is present in both mammals and birds and therefore possibly also in reptiles (reviewed in Peppard et al., 2005); an IgA-like molecule has now been identified in a lizard (Deza et al., 2007).

Purification, Properties and Extended Solution Structure of the Complex Formed between Human Immunoglobulin A1 and Human Serum Albumin by Scattering and Ultracentrifugation

Immunoglobulin A (IgA) is unique amongst antibodies in being able to form polymeric structures that may possess important functions in the pathology of specific diseases. IgA also forms complexes with other plasma proteins, the IgA1-human serum albumin (HSA) complex (IgA1-HSA) being typical. We have purified this complex using a novel two-step purification based on thiophilic chromatography and gel filtration, and characterised this. HSA is linked covalently to the tailpiece of IgA1 by a disulphide bond between Cys471 in IgA1 and Cys34 in HSA. IgA1-HSA binds to IgA receptors on neutrophils and monocytes, and elicits a respiratory burst that is comparable in magnitude to that of monomeric IgA1. The solution arrangement of IgA1-HSA was identified by X-ray scattering and ultracentrifugation. The radius of gyration R(G) of 7.5(+/-0.3) nm showed that IgA1-HSA is more extended in solution than IgA1 (R(G) of 6.1-6.2 nm). Its distance distribution function P(r) showed two peaks that indicated a well-separated solution structure similar to that for IgA1, and a maximum dimension of 25 nm, which is greater than that of 21 nm for IgA1. Sedimentation equilibrium showed that the IgA1:HSA stoichiometry is 1:1. Sedimentation velocity resulted in a sedimentation coefficient of 6.4S and a frictional ratio of 1.87, which is greater than that of 1.56 for IgA1. The constrained modelling of the IgA1-HSA structure using known structures for IgA1 and HSA generated 2432 conformationally randomised models of which 52 gave good scattering fits. The HSA structure was located at the base of the Fc fragment in IgA1 in an extended arrangement. Such a structure accounts for the functional activity of IgA1-HSA, and supports our previous modelling analysis of the IgA1 solution structure. The IgA1-HSA complex may suggest the potential for creating a new class of targeted therapeutic reagents based on the coupling of IgA1 to carrier proteins.

Identification and isolation from breast milk of ceruloplasmin-lactoferrin complex

The presence of a complex of the copper-containing protein ceruloplasmin (Cp) with lactoferrin (Lf) in breast milk (BM) is shown for the first time. In SDS-free polyacrylamide gel electrophoresis (PAGE), electrophoretic mobility of Cp in BM is lower than that of plasma Cp, coinciding with the mobility of the complex obtained upon mixing purified Cp and Lf. Affinity chromatography of delipidated BM on Cp-Sepharose resulted in retention of Lf. SDS-PAGE of the 0.3 M NaCl eluate revealed a single band with Mr approximately 78,000 that has the N-terminal amino acid sequence of Lf and reacts with antibodies to that protein. Synthetic peptides R-R-R-R (the N-terminal amino acid stretch 2-5 in Lf) and K-R-Y-K-Q-R-V-K-N-K (the C-terminal stretch 29-38 in PACAP 38) caused efficient elution of Lf from Cp-Sepharose. Cp-Lf complex from delipidated BM is not retained on the resins used for isolation of Cp (AE-agarose) and of Lf (CM-Sephadex). Anionic peptides from Cp--(586-597), (721-734), and (905-914)--provide an efficient elution of Cp from AE-agarose, but do not cause dissociation of Cp-Lf complex. When anti-Lf is added to BM flowed through CM-Sephadex, Cp co-precipitates with Lf. Cp-Lf complex can be isolated from BM by chromatography on CM-Sephadex, ethanol precipitation, and affinity chromatography on AE-agarose, yielding 98% pure complex. The resulting complex Cp-Lf (1 : 1) was separated into components by chromatography on heparin-Sepharose. Limited tryptic hydrolysis of Cp obtained from BM and from blood plasma revealed identical proteolytic fragments.

The antimicrobial function of milk lipids

Milk lipids serve not only as nutrients but as antimicrobial agents that constitute a defense system against microbial infections that occur at mucosal surfaces. The lipid fraction of milk develops antimicrobial activity in the gastrointestinal tract of suckling neonates as a result of lipolytic activity which converts milk triglycerides to antimicrobial fatty acids and monoglycerides. Antimicrobial milk lipids may be particularly important in protecting infants with an inadequate secretory immune response from infection. The lipid-dependent antimicrobial activity of milk is due to medium-chain saturated and long-chain unsaturated fatty acids and their respective monoglycerides released by lipases in the gastrointestinal tract. The antimicrobial activity of fatty acids and monoglycerides is additive and consequently it is their combined concentration that determines the lipid-dependent antimicrobial activity of milk. Microbial inactivation occurs rapidly by membrane destabilization. The antimicrobial activity of milk lipids can be duplicated using purified fatty acids and monoglycerides. It should be possible, therefore, to supplement banked human milk to provide lipid-dependent antimicrobial activity from the moment of ingestion (Schanler et al., 1986). This could reduce the risk of viral transmission from mother to infant through milk. Milk lipids also could be adapted for use at mucosal surfaces other than those in the gastrointestinal tract to reduce vertical transmission of pathogens during birth.

False positivity of enzyme-linked immunosorbent assay for measurement of secretory IgA antibodies directed at HIV type 1 antigens

We have determined that polymeric IgA in saliva of HIV-1-uninfected individuals binds in varying degrees to components of culture supernatants containing HIV-1 recombinant proteins when ELISA is used for the determination. This finding did not extend to salivary IgG antibodies. Further, such problems were not encountered in Western blot. Binding did not appear to be mediated by salivary proteins known to bind to IgA, including secretory component, amylase, lactoferrin, lysozyme, galactosyl transferase, or secretory leukocyte protease inhibitor, and was not influenced by blocking reagents or by changes in secondary anti-IgA antibodies. Although these findings will not likely impact on the use of saliva as a diagnostic fluid for HIV-1 infection (the HIV-1 response in saliva is mostly of the IgG isotype), they indicate that assessments of this secretion as an indicator of IgA mucosal immune responses to HIV-1 vaccines should be undertaken with caution.

Interaction of lactoferrin with ceruloplasmin

When added to human blood serum, the iron-binding protein lactoferrin (LF) purified from breast milk interacts with ceruloplasmin (CP), a copper-containing oxidase. Selective binding of LF to CP is evidenced by the results of polyacrylamide gel electrophoresis, immunodiffusion, gel filtration, and affinity chromatography. The molar stoichiometry of CP:LF in the complex is 1:2. Near-uv circular dichroism spectra of the complex showed that neither of the two proteins undergoes major structural perturbations when interacting with its counterpart. K(d) for the CP/LF complex was estimated from Scatchard plot as 1.8 x 10(-6) M. The CP/LF complex is found in various fluids of the human body. Upon injection into rat of human LF, the latter is soon revealed within the CP/LF complex of the blood plasma, from where the human protein is substantially cleared within 5 h.

Identification of lactoferrin complexes in bovine mammary secretions during mammary gland involution

Part of the antimicrobial activity of lactoferrin resides in its ability to bind to bacteria. The complexing of lactoferrin with other proteins could alter its activity. This study identified the presence of lactoferrin complexes in mammary secretions during mammary gland involution and determined the proportion of free and complexed lactoferrin in mammary secretions. Mammary secretions were collected from Holstein cows on d 7, 14, and 21 of involution. Proteins were fractionated from defatted, filtered mammary secretions by sucrose density gradient ultracentrifugation and by gel filtration chromatography. Proteins contained in separated fractions were identified by SDS-PAGE. The presence of lactoferrin was confirmed by immunoblot analysis. Lactoferrin was present as complexed forms of high molecular mass in mammary secretions at each day of involution. The majority of lactoferrin was present in complexes of higher molecular mass rather than as monomers. A majority of lactoferrin existed in fractions of approximately 250 kDa, although peaks of lactoferrin at 150, 300, and 800 kDa were also found. The presence of lactoferrin complexes may result from interactions with casein or immunoglobulins or from the formation of lactoferrin multimers in the secretions. The interaction of lactoferrin with other proteins in mammary secretions during involution may affect the antimicrobial properties of lactoferrin.

Determinant of bacterial translocation in the newborn: small bowel versus large bowel colonization

This study investigated the relationship between bacterial translocation (BT) and small and large bowel bacterial colonization in the neonatal rabbit. The authors have previously shown that spontaneous BT occurs in rabbits during the first week of life, but is less frequent before the third day of life. The authors have also shown that bacterial colonization of the small bowel, is delayed until 3 to 5 days of age, and is preceded by colonization of the large bowel. Therefore, the authors hypothesizes that BT is dependent on small bowel, not large bowel, colonization. New Zealand White rabbit pups (n = 255) were divided into four groups, formula-fed (FF), formula-fed plus antibiotic (FFAB), breast-fed (BF) and unfed controls (UC). Animals from each group were killed on day 1 to 4 of life. Small bowel (SB) and large bowel (LB) specimens, mesenteric lymph nodes (MLN), spleen (SPL), and liver (LIV) were obtained from each rabbit, incubated for 24 hours in thioglycolate broth, and plated on both MacConkey and Colistin Naladixic Acid media in an aerobic environment. After 24 hours, growth on either plate was recorded. Bacterial colonization was significantly greater in FF versus UC, BF, and FFAB rabbit groups. In addition, large bowel colonization was significantly increased compared with small bowel colonization in all feeding groups (P < .05). Bacterial translocation to MLN, SPL, and LIV ranged from 10% to 27% in all groups. Gram-negative bacteria predominated over gram-positive bacteria in translocation to the various tissues sampled.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of heat treatment and other milk proteins on the interaction of lactoferrin with monocytes

The interaction of lactoferrin from human and bovine milk with the human promonocytic cell line U937 has been studied. Both human and bovine Fe-lactoferrins bound to the cells. Binding of bovine lactoferrin was inhibited by excess bovine lactoferrin but not by human lactoferrin, suggesting that the binding mechanisms for the two proteins are different. Binding of human but not bovine lactoferrin was inhibited by bovine lactoperoxidase, while a 20-fold excess of human IgA inhibited binding of human but not bovine lactoferrin. Human and bovine alpha-lactalbumins, bovine beta-lactoglobulin, and human lysozyme had no effect on binding of lactoferrin from either species. Samples of bovine Fe- and apolactoferrin in capillary tubes were exposed to temperatures of 72 degrees C for 20 s, 85 degrees C for 20 min or 137 degrees C for 8 s. All the heated samples inhibited binding of native Fe- and apolactoferrin, though to a lesser extent than the native proteins. Both heated and native lactoferrins enhanced [3H]thymidine incorporation by U937 cells, except for Fe-lactoferrin heated at 85 degrees C for 20 min, which was inhibitory. These results suggest that heat treatment of lactoferrin under conditions used for industrial processing does not greatly affect its ability to interact with and stimulate monocytic cells, and that other milk proteins in general do not interfere with lactoferrin-monocyte interactions. It may thus be feasible to incorporate biologically active lactoferrin into infant formulas.

Agglutination of Streptococcus mutans serotype C cells but inhibition of Porphyromonas gingivalis autoaggregation by human lactoferrin

The ability of various forms of human lactoferrin (LF) to agglutinate oral Streptococcus mutans, Strep. sobrinus, Strep. rattus, Strep. sanguis, Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans cells was studied spectrophotometrically. Fe3+ saturated LF was unable to agglutinate these bacteria, whereas iron-free LF (apo LF) effectively agglutinated Strep. mutans cells but not the other bacteria. The efficiency and rate of agglutination of Strep. mutans were somewhat lower with apo LF than with human whole saliva. However, secretory IgA, phosphate and whole saliva almost totally abolished the apo LF-mediated agglutination of Strep. mutans, suggesting binding to the same target sites on bacterial cell surfaces, or to each other. The presence of exogenous iron (Fe2+, Fe3+), lactoperoxidase or serum albumin did not affect the agglutination by apo LF. Low Ca2+ (50-100 microns) slightly enhanced the agglutination by apo LF but higher concentrations (0.5-1.0 mM) totally blocked the apo LF-mediated agglutination of Strep. mutans. Both saliva and apo LF significantly delayed the rapid autoaggregation of P. gingivalis cells. Aggregation of P. gingivalis is considered a potential virulence factor and a protective mechanism against the host's cellular defences in the gingival crevice. These findings show a novel, strain-specific antibacterial mechanism for LF against Strep. mutans and P. gingivalis and adds a new compound to the group of agglutinating proteins in human saliva.

Interactions of galactosyltransferase with serum and secretory immunoglobulins and their component chains

Assay of the activity of beta-1,4-galactosyltransferase (beta-1,4-GT) revealed that in addition to serum, milk, colostrum, amniotic and cerebrospinal fluids and malignant effusions, this enzyme is present also in tears and saliva. Molecular-sieve chromatography of human colostral whey and serum and subsequent assay of beta-1,4-GT activity have shown that beta-1,4-GT was present as a free enzyme (55 kDa) and associated with components of larger molar mass. The elution pattern did not change when the chromatography was carried out in a buffer devoid of, or enriched with, Mn2+, a cofactor of beta-1,4-GT activity. However, the activity associated with the large molar mass components was absent when the chromatography was carried out in the presence of a chelating agent (EDTA). Analyses of the eluted material by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE), and by immunodiffusion indicated that the major colostral component in beta-1,4-GT activity-containing fractions was secretory IgA (S-IgA); in addition, the beta-1,4-GT activity was detected in fractions that contained lactoferrin and alpha-lactalbumin. Interactions of beta-1,4-GT with S-IgA and lactoferrin in colostrum were also demonstrated by the detection of radioactivity in precipitin lines obtained by immunoelectrophoresis and autoradiography of the colostral whey after it had been incubated with UDP-[3H]-galactose. Furthermore, radioactively labeled S-IgA and alpha-chain were detected when colostral whey incubated with UDP-[3H]-galactose was analyzed by SDS-PAGE under non-reducing and reducing conditions, respectively. In serum, the beta-1,4-GT-binding components identified in fractions after molecular-sieve chromatography were IgG, IgA, IgM and transferrin. The binding of beta-1,4-GT to immunoglobulins (Ig) was also demonstrated by assaying the beta-1,4-GT activity associated with Sepharose-4B-immobilized Ig of various isotypes and molecular forms, which were incubated with colostral beta-1,4-GT in the presence of Mn2+. Beta-1,4-GT measured by enzyme activity was bound to these Ig in order: polymeric IgA2 > monomeric IgA1 = polymeric IgA1 = secretory IgA = pentameric IgM > IgG. Immobilized component chains, namely alpha, mu and J chains, bound beta-1,4-GT more effectively than native Ig. Incubation of the IgA1 myeloma protein with crude human colostral galactosyltransferase in the presence of UDP[3H]-galactose and Mn2+ resulted in galactosylation of both N- and O-linked carbohydrate side chains.(ABSTRACT TRUNCATED AT 400 WORDS)

Mucosal defense mechanism in health and disease. Role of the mucosal immune system

The mucosal immune system is characterized predominantly by the secretory antibody response and gut-associated lymphoid tissue, cellular part of the mucosal immune system. The secretory antibody system depends on local production and selective epithelial transport of secretory IgA and IgM. Furthermore, secretory antibodies and interactions between the intestinal epithelium and T cells are involved in the mucosal down-regulation of the systemic immune system. Neuropeptides play a crucial role in the regulation of mucosal immune responses. It is possible that impairment of the mucosal immune response contributes to the pathogenesis of various intestinal diseases, such as inflammatory bowel disease. Until recently, however, mucosal immunity received relatively little attention from both basic and clinical scientists. Further research on mucosal immunity seems to have promise in helping to provide new understanding of the immune mechanisms and pathogenesis of several gastrointestinal and systemic diseases.

Different profiles of induced cotton effects of human and bovine lactoferrin by cibacron blue F3GA binding

1. The properties of complex formation of lactoferrin with Cibacron Blue F3GA dye have been studied by circular dichroic spectral analyses. The Cotton effects were induced by the interaction of lactoferrin with the dye and occurred in the wavelength range from 300 to 450 nm. 2. The patterns of changes in circular dichroic spectra of lactoferrin induced by the dye were different in bovine and human lactoferrin. 3. Iron ions bound to lactoferrin affected the profiles of induced Cotton effects in human lactoferrin but not in bovine lactoferrin. 4. While the dye bound co-operatively to human apo-lactoferrin, such co-operativeness was not observed in iron-saturated human lactoferrin.

The relationship between 48-h dental plaque accumulation in young human adults and the concentrations of hypothiocyanite, 'free' and 'total' lysozyme, lactoferrin and secretory immunoglobulin A in saliva

Samples of resting and stimulated whole saliva and stimulated parotid saliva were collected from 40 young adults. One week later, after 48 h on a standardized diet without oral hygiene, all available plaque was collected for dry weighing. An inverse relationship was found between the 'free' lysozyme concentration in stimulated parotid saliva and plaque dry weight (r = -0.46, p less than 0.01). There were no other statistically significant correlation coefficients between concentrations of individual salivary constituents and plaque dry weight. However, cluster analysis of constituents in resting whole saliva revealed three groups of subjects with different salivary profiles, and in particular with different concentrations of both IgA and hypothiocyanite. Subsequent analysis revealed differences in plaque dry weight between the groups, demonstrating the potential biological significance of cluster membership based on salivary factors.

Antimicrobial proteins in human unstimulated whole saliva in relation to each other, and to measures of health status, dental plaque accumulation and composition

Saliva antimicrobial proteins may interact in a common system to influence the oral ecology. Clinical studies of antimicrobial protein action thus may require a multiple-protein approach. Multivariate statistical methods have been used to describe possible patterns of interaction for lysozyme, lactoferrin, salivary peroxidase and secretory IgA in stimulated parotid saliva. However, oral microbes are most likely to encounter antimicrobial proteins in mixed resting saliva. Relationships among levels of lysozyme, lactoferrin, salivary peroxidase, and secretory IgA therefore were investigated in whole saliva from 216 subjects, and an attempt made to relate interperson variation in those proteins to differences in health and status, and dental plaque accumulation and composition. All proteins were significantly (alpha = 0.05) correlated with each other (r = 0.38-0.52, p less than 0.001). There was only one axis of common variation among proteins, and that axis was significantly correlated (p less than 0.001) with total protein (r = 0.84) and flow rate (r = -0.56). That pattern deviated from the previous finding that proteins of acinar origin tended to vary independently from proteins of ductal origin in stimulated parotid saliva. The difference between parotid and whole saliva may reflect constitutive secretion of all proteins at low levels of stimulation. Common variation of unstimulated saliva proteins suggests that antimicrobial actions can be compared in subjects at population extremes. There were no significant associations between antimicrobial proteins in whole saliva and measures of health status or plaque accumulation. However, the proportions of Streptococcus sanguis were significantly correlated with lysozyme (r = -0.26), lactoferrin (r = -0.34), peroxidase (r = -0.30), total protein (r = -0.37), flow rate (r = 0.24) and principal-components scores (r = -0.33) in a subset of subjects (n = 85) where commercial biochemical tests were used to supplement species identification by colony morphology. Those findings may indicate that saliva antimicrobial proteins can affect the composition of dental plaque.

Interaction of bovine lactoferrin with other proteins of milk whey

The association between bovine lactoferrin and the major bovine whey proteins, beta-lactoglobulin, alpha-lactalbumin and albumin has been studied by immunochemical techniques, gel filtration and affinity chromatography in lacteal secretions and using purified proteins. Bovine lactoferrin is able to form non-covalent complexes with beta-lactoglobulin or albumin, with lactoferrin-protein molar ratios of 2:1 and 1:1 respectively. No association was detected with alpha-lactalbumin. Lactoferrin interacts with beta-lactoglobulin-Sepharose at low ionic strength, but not in the presence of 0.3 M NaCl, indicating that ionic interactions are important. The lack of association with alpha-lactalbumin suggests however a certain degree of specificity in this electrostatic interaction.

Studies on the relationships of IgA to human liver. IgA deposition in non-alcoholic liver diseases

An investigation was conducted to clarify the relationships of IgA to the human liver. Immunocytochemical studies were performed on biopsy specimens from patients with cirrhosis and chronic hepatitis without any apparent history of alcohol abuse. The results showed that 1) a large amount of IgA is associated with the sinusoidal surface of hepatocytes, endothelial cells and Kupffer cells, 2) this IgA contains J chain and can form a complex with secretory component, and 3) this mainly belongs to the IgA1 subclass, 4) IgA in vesicles within hepatocytes and Kupffer cells is always associated with acid phosphatase activity, and 5) IgA containing vesicles within ductular epithelial cells always lack such enzyme activity. We conclude that 1) the IgA bound to the surface of hepatocytes, sinus endothelial cells and Kupffer cells is polymeric IgA1 uncomplexed with SC, and 2) this IgA occasionally enters these cells, and may be degraded in the lysosomes. 3) Polymeric IgA combines with SC in the ductular epithelium and may be secreted into bile. These findings suggest that J chain-linked polymeric IgA bound to the surface of hepatocytes and Kupffer cells has a certain pathological significance in liver diseases and might be involved in the clearance of excess IgA from the circulation.

Purification and characterization of bovine lactoferrin from secretions of the involuting mammary gland: identification of multiple molecular weight forms

1. Lactoferrin was isolated from bovine mammary secretions collected during the nonlactating period. 2. A method utilizing heparin-agarose affinity chromatography was more efficient for purifying lactoferrin than a method including gel filtration, ion exchange chromatography and a second gel filtration. 3. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that the purified lactoferrin was composed of two protein bands of apparent mol. wt. of 83,000 and 87,000. 4. Digestion with endoglycosidase H resolved the lactoferrin into two lower mol. wt. bands of 78,000 and 81,000. 5. The biochemical differences between the forms of lactoferrin are not exclusively due to differences in endoglycosidase H-sensitive oligosaccharide composition.

Relationships between human parotid saliva lysozyme lactoferrin, salivary peroxidase and secretory immunoglobulin A in a large sample population

Saliva antimicrobial proteins may interact in a common system for host defence. This study applied multivariate analysis as a means of describing inter-person variation in that system. Samples of stimulated parotid saliva were obtained from 198 subjects. Flow rate was determined, and assays run for total protein, lysozyme, lactoferrin, salivary peroxidase and secretory IgA. Correlation and principal components analysis were used to define the relationships between proteins; cluster analysis was used to identify persons with similar protein concentration profiles. All proteins were significantly correlated at p less than 0.002 (r = 0.20-0.52). Principal components analysis identified a major axis of common variation, defined by lysozyme and salivary peroxidase, and a second axis, defined by secretory IgA. Lactoferrin was associated with both axes. Seven major groupings were obtained by cluster analysis; these were significantly different at p less than 0.001. Such groupings may prove useful in comparing the antimicrobial properties of saliva samples.

Immunological functions of the gut--role of the mucosal immune system

This review summarizes recent information about immune responses in the intestinal mucosa with emphasis on the role of orally-administered antigens from the external environment. The intestinal mucosa provides an extensive surface for potential absorption of pathogenic environmental antigens, such as microbes, chemicals, and food. The intestinal mucosa is densely populated by IgA-producing plasma cells. The humoral immune responses to antigens in the intestinal mucosa are largely of the IgA class in secretory form (sIgA). This sIgA provides an immunological barrier to absorption of antigens on the mucosal epithelium and to penetration into the body. The cell-mediated immune mechanism is also equipped in the mucosal sites. In addition, the mucosal immune response induces hyporesponsiveness of nonmucosal (systemic) immune reactions, and the liver is an integral part of the mucosal immune system. Thus we consider that the mucosal immune system plays a central role in the maintenance of the homeostasis of the total immune system.

Binding of immunoglobulins to the major progesterone-induced proteins secreted by the sheep uterus

We examined the binding of immunoglobulins to the uterine milk proteins, the major progesterone-induced proteins secreted by uterine endometrium of pregnant ewes. Binding was ascertained by measuring binding of 125 I-immunoglobulin to uterine milk proteins that were Western or dot-blotted to nitrocellulose or were coupled to Sepharose. The magnitude of binding was greatest for sheep IgM, intermediate for sheep secretory IgA, low for human secretory and serum IgA, and barely detectable for sheep IgG. Binding of IgA and IgM to uterine milk proteins was time and concentration dependent, saturable, inhibited by high ionic strength buffers, and lost due to enzymatic destruction of the Fc portion of the immunoglobulin molecule. In conclusion, the uterine milk proteins preferentially bind IgA and IgM in a species-dependent manner. Such binding may be related to the role of these proteins in the uterus and may make the uterine milk proteins a useful tool for studying or purifying sheep immunoglobulins.

Isolation and characterisation of lactoferrin separated from human whey by adsorption chromatography using Cibacron Blue F3G-A linked affinity adsorbent

A new one-step procedure for isolating lactoferrin from human whey using Cibacron Blue affinity chromatography is described. Characteristics of the isolated lactoferrin include pI 5.5-6.1 and differential migration on SDS-polyacrylamide gel electrophoresis of apo and iron saturated lactoferrin. The concentration of lactoferrin in breast milk varies with time after parturition but the iron saturation remains relatively constant with time.

Immunocytochemical and enzymecytochemical studies on the intracellular transport mechanism of secretory immunoglobulin A and lactoferrin in human salivary glands

The intracellular transport mechanism of secretory immunoglobulin A (sIgA) has been immunocytochemically defined in human submandibular glands. To examine the properties of the intracytoplasmic vesicles which contain IgA, the enzyme labeled antibody method for SC and IgA and Novikoff's method for acid phosphatase (ACPase) activity were employed on the same sections. The intracytoplasmic vesicles containing IgA and SC in the serous acinar cells were free of ACPase activity and were thus distinguishable from lysosomes. Neither IgA nor SC was localized in the secretory granules. Lactoferrin was localized in the secretory granules and glandular lumen of the serous acinar cells, but not in the cytoplasmic vesicles, which were also free of ACPase activity. These findings suggests that the transport of sIgA was performed by intracytoplasmic vesicles and that lactoferrin is discharged from secretory granules into the lumen and finally makes a "rendezvous" with sIgA in the lumen of acinar cells.