Review

Important Animal Allergens Are Lipocalin Proteins: Why Are They Allergenic?
Tuomas Virtanen, Thomas Zeiler, Rauno Mäntyjärvi

Department of Clinical Microbiology, University of Kuopio, Kuopio, Finland

Address of Corresponding Author

Int Arch Allergy Immunol 1999;120:247-258 (DOI: 10.1159/000024277)

  Key Words

• Allergen
• Allergenicity
• Animal allergen
• Epitope
• Immune response
• Lipocalin
• T cell
• Tolerance

  Abstract

Major respiratory allergens of dogs, mice, rats, horses and cows belong to the lipocalin group of proteins. The sequence identity of lipocalins is often less than 20%, but they contain between one and three structurally conserved regions and their three-dimensional structures are similar. Lipocalins share common biological functions, predominantly related to the transport of small hydrophobic molecules, such as vitamins and pheromones. Immune reactivity to lipocalin allergens is not well known. In Bos d 5, the IgE-binding epitopes are spread along the molecule, whereas in Bos d 2, the C terminus appears to contain the human B cell epitopes. Bos d 5 contains several murine T cell epitopes. No information is available on human T cell epitopes. The maximal number of epitopes an allergic patient's T cells could recognize in Bos d 2 was five. Three of the epitopes were colocalized in the structurally conserved regions of lipocalins. Interestingly, one of the epitopes was recognized by the T cells of all patients and the computer predictions suggested that there would be an epitope in the corresponding parts of human endogenous lipocalins. The proliferative responses of peripheral blood mononuclear cells of Bos d 2-allergic subjects to Bos d 2 were weak. The T cell response was Th2-dominated. To explain these observations, we have proposed that the allergenicity of lipocalins may be a consequence of molecular mimicry between lipocalin allergens and endogenous lipocalins at the T cell level.

  Author Contacts

Correspondence to: Dr. Tuomas Virtanen
Department of Clinical Microbiology, University of Kuopio
POB 1627, FIN-70211 Kuopio (Finland)
Fax +358 17 162705, E-Mail tuomas.virtanen@uku.fi

  Article Information

Number of Print Pages : 12
Number of Figures : 2, Number of Tables : 0, Number of References : 161