Casadevall et al. (March 7 issue)¹ described the development of autoantibodies against erythropoietin in a patient with pure red-cell aplasia. The authors report the presence of IgG antibodies against endogenous erythropoietin, but there are few reports on antibodies against recombinant human erythropoietin (rHuEPO).^2-4

Recombinant human erythropoietin (rHuEPO) is a sialoglycoprotein hormone that appears to be immunologically and biologically equivalent to the endogenous compound, enhancing erythropoiesis dose-proportionally. The recombinant product is structurally very similar, if not identical, to native human erythropoietin, being a 193-amino acid peptide from which a 27-amino acid leader sequence is cleaved. Evidence indicates that the arginyl residue at the carboxyl terminus is also removed. The 165-amino acid mature protein contains two disulfide bonds, and one O-linked and three N-linked carbohydrate chains. The major carbohydrate units are sialated tetraantennary saccharides, which are required for stability in vivo ( 1). Two different rHuEPO products have been developed, alpha and beta, with differences in carbohydrate structure (glycoforms). In spite of the fact that rHuEPO is produced in mammalian cell lines and despite its widespread use, relatively little information is available regarding its immunogenic character. To date, few reports have been published on the development of anti-rHuEPO antibodies ( 2)( 3)( 4)( 5).

Food allergy represents an increasing health problem, with children being the most affected population. The symptoms can appear within minutes or hours of ingesting the offending food, producing skin manifestations, respiratory, gastrointestinal and anaphylactic reactions in the severe forms. Food allergy is established by the loss of tolerance to food proteins, and is characterized by an altered balance of regulatory T (Treg) cells and the shift to Th2 type cytokines in the intestinal lamina propria. We have described the contribution of different factors in establishing oral tolerance, such as the antigenic exposition route, the gut microenvironment, and the timing of the food introduction. Apart from avoiding the food, immunotherapy is the only intervention which produces oral desensitization to food proteins. Among the underlying immunological mechanisms of oral immunotherapy (OIT) are the changes in humoral immunity (a decrease of allergen-specific IgE and an increase of allergen-specific IgG4) and cellular changes such as the increased number of FoxP3⁺ Treg cells. At present, the experiences of OIT with various foods are offering promising results. OIT appears to be safe producing low adverse reactions, and effective in inducing desensitization in most subjects with food allergy.