Short communication IgE, IgG1, and IgG4 antibody responses to Blomia tropicalis in atopic patients The role of house dust mites (HDMs) as an allergen source and their contribution in allergic diseases, particularly asthma and rhinitis, has been recognized for many years (1). Dermatophagoides pteronyssinus, D. farinae, and Blomia tropicalis are predominant mites in house dust samples in tropical countries (2). Concurrent sensitization can occur in houses where both D. pteron- yssinus and B. tropicalis are found, thus complicating etiologic diagnosis and therapeutic treatment in atopic patients. Although inhibition studies have suggested that B. tropicalis allergens are species-specific, antibody cross-reactivity with D. pteronyssinus antigens was esti- mated at approximately 30% (3). An important allergen from B. tropicalis (Blo t 5) has 43% sequence homology to Der p 5 allergen from D. pteronyssinus, while no cross-reactivity was found between groups 1 and 2 allergens from D. pteronyssinus and other B. tropicalis allergens (1, 3). The role of immunoglobulin (Ig)G subclasses to HDM allergens in the pathogenesis of allergic diseases remains unclear. The IgG4 has been found to have a protective role attributable to prolonged natural antigenic exposure and antigen neutralization, or IgE blocking. This pro- tective activity may be a significant underlying mechan- ism for the efficacy of immunotherapy (4, 5). This study was aimed at evaluating the IgE, IgG1, and IgG4 antibody responses to B. tropicalis in patients with allergic rhinitis (AR) with/without asthma sensitized to B. tropicalis alone or concomitantly to both B. tropicalis and D. pteronyssinus. The IgE-, IgG1-, and IgG4-binding proteins derived from Blomia were also investigated by immunoblotting. Background: Allergens from house dust mites (HDMs), Dermatophagoides pteronyssinus and Blomia tropicalis are clinically relevant in atopic respiratory diseases in tropical countries. Aims of the study: To evaluate immunoglobulin (Ig)E, IgG1, and IgG4 antibody responses to B. tropicalis in Brazilian atopic patients. Methods: About 110 patients with allergic rhinitis with/without asthma and 33 control subjects underwent skin prick testing (SPT) with HDM extracts, and their sera were tested for IgE and IgG subclass antibodies to D. pteronyssinus and B. tropicalis by enzyme-linked immunosorbent assay (ELISA) and immunoblotting. Results: Most patients (56%) had positive SPT to B. tropicalis extract (B. tropicalis+ group), although 51% were reactive to both B. tropicalis and D. pteronyssinus and 6% were sensitized to B. tropicalis only. IgE-ELISA detected 43% B. tropicalis positivity with high-specific IgE levels in B. tropicalis+ patients. Specific IgG4 levels were higher in B. tropicalis+ than B. tropicalis) groups and correlated with specific IgE levels. The IgG1 levels to B. tropicalis were higher in patients than controls. The major allergenic B. tropicalis components recognized by B. tropicalis+ patient sera were the 54, 66, and 68 kDa proteins. The IgG4-binding protein profiles closely resembled that of IgE. The IgG1 antibodies recognizing multiple B. tropicalis protein species were detected in sera of all three patient groups. Conclusions: A large percentage of our allergic patients are B. tropicalis+. They are more frequently sensitized to high-molecular weight (HMW) B. tropicalis components than the major low-molecular weight (11–15 kDa) allergens detec- ted in other studies. The results suggest that HMW B. tropicalis antigenic components are potential candidates for evaluating allergen exposure and sensitization, and for immunotherapy treatment. E. A. L. Pereira 1 , D. A. O. Silva 1 , J. P. Cunha-Jfflnior 2 , K. C. Almeida 1 , R. Alves 1 , S. J. Sung 3 , E. A. Taketomi 1 1 Division of Immunology, Institute of Biomedical Sciences, Federal University of Uberlândia, MG, Brazil; 2 Division of Immunology and Microbiology, Department of Biological Sciences, State University of Santa Cruz, IlhØus, BA, Brazil; 3 Division of Rheumatology and Immunology, Health Sciences Center, University of Virginia, Charlottesville, VA, USA Key words: allergic rhinitis; Blomia tropicalis; immunoglobulin E; immunoglobulin G1; immunoglobulin G4. E. A. Taketomi MD, PhD Disciplina de Imunologia Instituto de CiÞncias BiomØdicas Universidade Federal de Uberlândia Av Parµ 1720 Campus Umuarama CEP 38400-902 Uberlândia MG Brasil Accepted for publication 26 July 2004 Allergy 2005: 60: 401–406 Copyright Ó Blackwell Munksgaard 2005 ALLERGY DOI: 10.1111/j.1398-9995.2005.00738.x 401