Anti-human serum albumin autoantibody may be involved in the pathogenesis of autoimmune bullous skin diseases

Albumins represent highly cross-reactive animal allergens

Albumins from animals are highly cross-reactive allergens for patients suffering from immunoglobulin E (IgE)-mediated allergy. Approximately 20-30% of cat and dog allergic patients show IgE reactivity and mount IgE-mediated allergic reactions to cat and dog albumin. It is astonishing that allergic patients can develop specific IgE responses against animal albumins because these proteins exhibit a more than 70% sequence identity to human serum albumin (HSA) which is the most abundant protein in the blood of the human body. The sequence identity of cat albumin (Fel d 2) and dog albumin (Can f 3) and HSA are 82% and 80%, respectively. Given the high degree of sequence identity between the latter two allergens and HSA one would expect that immunological tolerance would prohibit IgE sensitization to Fel d 2 and Can f 3. Here we discuss two possibilities for how IgE sensitization to Fel d 2 and Can f 3 may develop. One possibility is the failed development of immune tolerance in albumin-allergic patients whereas the other possibility is highly selective immune tolerance to HSA but not to Fel d 2 and Can f 3. If the first assumption is correct it should be possible to detect HSA-specific T cell responses and HSA-containing immune complexes in sensitized patients. In the latter scenario few differences in the sequences of Fel d 2 and Can f 3 as compared to HSA would be responsible for the development of selective T cell and B cell responses towards Fel d 2 as well as Can f 3. However, the immunological mechanisms of albumin sensitization have not yet been investigated in detail although this will be important for the development of allergen-specific prevention and allergen-specific immunotherapy (AIT) strategies for allergy to albumin.

Case Report: Variety of Target Antigens During 1 Year Follow-Up of a Patient Initially Diagnosed With Bullous Pemphigoid

Autoimmune bullous diseases (AIBDs), presenting cutaneous and/or mucosal bullous lesions, are classified into pemphigus and pemphigoid diseases. A longtime observation for complicated AIBD cases is rarely reported. In this study, serum samples of one AIBD patient were collected at seven different time points during the disease course including a relapse, which were examined by our conventional and newly developed methods for the detection of autoantibodies. Interestingly, we found changes of both the presence and the titers of various autoantibodies in accordance with the changes of clinical features during the whole disease course, which indicated that the patient started as bullous pemphigoid and relapsed as concurrence of bullous pemphigoid and mucosal-dominant-type pemphigus vulgaris.

Increased sensitivity of gp210 autoantibody detection using a newly designed gp210 antigen

OBJECTIVES

The detection of autoantibody to glycoprotein 210 (gp210 Ab) against a 15 amino-acid peptide epitope by enzyme-linked immunosorbent assay (ELISA) has been widely used in the diagnosis of primary biliary cholangitis (PBC). However, this small peptide antigen presents spatial limitations for antibody access, which reduces the sensitivity of autoantibody detection. A recombinant gp210 antigen was constructed for increased sensitivity in antibody detection is described here.

METHODS

The gp210 C terminal 18 amino acid coding sequence was ligated to the modified C-terminal 108 amino acid coding sequence of human serum albumin (mHSA108) and produced as a recombinant gp210 antigen mHSA108-gp210-C18. Measurements of gp210 Ab using the gp210 C-terminal 25 amino acid peptide (gp210-C25) and mHSA108-gp210-C18 by in-house ELISA were compared. ELISAs with mHSA108-gp210-C18 and commercial INOVA kit for gp210 Ab detection were also compared in PBC patients and healthy controls. The correlation between the two assays was analyzed and their efficiency in diagnosing was compared.

RESULTS

Of 86 PBC samples, 35 (40.70%) and 44 (52.33%) positive samples were detected for anti-gp210 Ab using gp210-C25 and mHSA108-gp210-C18, respectively. Of 252 samples from PBC, 114 (45.24%) were positive for mHSA108-gp210-C18 ELISA whereas 94 (37.3%) for commercial ELISA (INOVA). All positive samples detected with commercial ELISA kit were also tested positive in mHSA108-gp210-C18 ELISA. Among 374 patients with other autoimmune diseases, anti-gp210 Ab were detected by mHSA108-gp210-C18 ELISA in 0.95% systemic lupus erythematosus (SLE) patients (2/210), 13.04% rheumatoid arthritis (RA) patients (13/97), and 1.47% of Sjögren's Syndrome (SS) patients (1/67).

CONCLUSIONS

Compared to the gp210 peptide antigen, the sensitivity of the ELISA system using mHSA108-gp210-C18 antigen was improved. The novel gp210 antigen could be useful for screening patients known to be at increased risk of developing PBC.

Integrative Role of Albumin: Evolutionary, Biochemical and Pathophysiological Aspects

Being one of the main proteins in the human body and many animal species, albumin plays a crucial role in the transport of various ions, electrically neutral molecules and in maintaining the colloidal osmotic pressure of the blood. Albumin is able to bind almost all known drugs, many nutraceuticals and toxic substances, determining their pharmaco- and toxicokinetics. However, albumin is not only the passive but also the active participant of the pharmacokinetic and toxicokinetic processes possessing a number of enzymatic activities. Due to the thiol group of Cys34, albumin can serve as a trap for reactive oxygen and nitrogen species, thus participating in redox processes. The interaction of the protein with blood cells, blood vessels, and also with tissue cells outside the vascular bed is of great importance. The interaction of albumin with endothelial glycocalyx and vascular endothelial cells largely determines its integrative role. This review provides information of a historical nature, information on evolutionary changes, inflammatory and antioxidant properties of albumin, on its structural and functional modifications and their significance in the pathogenesis of some diseases.

Serum Albumin in Health and Disease: Esterase, Antioxidant, Transporting and Signaling Properties

Being one of the main proteins in the human body and many animal species, albumin plays a decisive role in the transport of various ions-electrically neutral and charged molecules-and in maintaining the colloidal osmotic pressure of the blood. Albumin is able to bind to almost all known drugs, as well as many nutraceuticals and toxic substances, largely determining their pharmaco- and toxicokinetics. Albumin of humans and respective representatives in cattle and rodents have their own structural features that determine species differences in functional properties. However, albumin is not only passive, but also an active participant of pharmacokinetic and toxicokinetic processes, possessing a number of enzymatic activities. Numerous experiments have shown esterase or pseudoesterase activity of albumin towards a number of endogeneous and exogeneous esters. Due to the free thiol group of Cys34, albumin can serve as a trap for reactive oxygen and nitrogen species, thus participating in redox processes. Glycated albumin makes a significant contribution to the pathogenesis of diabetes and other diseases. The interaction of albumin with blood cells, blood vessels and tissue cells outside the vascular bed is of great importance. Interactions with endothelial glycocalyx and vascular endothelial cells largely determine the integrative role of albumin. This review considers the esterase, antioxidant, transporting and signaling properties of albumin, as well as its structural and functional modifications and their significance in the pathogenesis of certain diseases.