doi: 10.1111/j.1365-2222.2011.03937.x Clinical & Experimental Allergy, 42, 412–422 ORIGINAL ARTICLE Basic Mechanisms in Allergic Disease © 2011 Blackwell Publishing Ltd Serine protease Per a 10 from Periplaneta americana bias dendritic cells towards type 2 by upregulating CD86 and low IL-12 secretions C. Goel 1 , D. Govindaraj 1 , B. P. Singh 1 , A. Farooque 2 , N. Kalra 2 and N. Arora 1 1 Allergy and Immunology Section, Institute of Genomics and Integrative Biology (CSIR), Delhi, India and 2 Division of Radiation Biosciences, Institute of Nuclear Medicine and Allied Sciences (DRDO), Delhi, India Clinical & Experimental Allergy Correspondence: Naveen Arora, Scientist, Room 509, Allergy and Immunology Section, Institute of Genomics and Integrative Biology, Delhi University Campus, Mall Road, Delhi-110007, India. E-mail: naveen@igib.res.in Cite this as: C. Goel, D. Govindaraj, B. P. Singh, A. Farooque, N. Kalra and N. Arora, Clinical & Experimental Allergy, 2012 (42) 412–422. Summary Background Serine protease activity of Per a 10 from Periplaneta americana induces air- way inflammation and systemic Th2 response towards self and bystander allergen. Objective In the present study the effect of proteolytic activity of Per a 10 allergen on dendritic cells (DCs) polarization and consequent T cell response was investigated. Methods Non-atopic subjects with no family history of asthma/allergy were recruited for the study. CD14 + peripheral blood monocytes were purified, differentiated to immature DCs and stimulated with proteolytically active/inactivated native or recombinant Per a 10. DCs phenotype was analysed with flow cytometry and antigen presenting function assessed by co-culturing with autologous CD4 + T cells. Cytokine levels were determined using ELISA. Results Immature DCs differentiated into mature CD14 - CD83 + HLA-DR + cells after incubat- ing with proteolytically active/inactivated or recombinant Per a 10. Proteolytically active Per a 10 induced significant CD86 up-regulation on DCs compared to inactivated or recombinant Per a 10 lacking enzymatic activity. Proteolytic activity of Per a 10 showed dose-dependent effect on expression of CD80, CD86, CD83, CD1a and HLA-DR. However, no significant differences were observed phenotypically in active or inactive forms except for CD86. Active Per a 10 stimulated DCs secreted significantly low IL-12 (P < 0.01) and high IL-6, compared to inactive forms of Per a 10. Naive CD4 + T cells primed with active Per a 10 pulsed DCs also secreted significantly less IL-12 (P < 0.01) and high IL-4, IL-5 plus IL-6 (P < 0.01); in contrast to DCs pulsed with inactivated or recombinant Per a 10. Conclusion and clinical relevance Proteolytic activity of Per a 10 modulates DCs towards type 2 by CD86 up-regulation, high IL-6 and reduced IL-12 secretions. Proteolytically inactive Per a 10 can be further explored for immunotherapy. Keywords allergen, DCs polarization, Per a 10, Periplaneta americana, proteolytic activity, serine protease Submitted 11 July 2011; revised 23 November 2011; accepted 25 November 2011 Introduction Cockroaches are potent source of allergens associated with type I allergy including asthma [1]. The presence of cockroaches in homes makes them significant indoor allergens and a risk factor among inner-city children [2]. Periplaneta americana extracts show sensitization in 7–55% of atopic population in different countries [1, 3]. Several proteins were identified from P. americana and demonstrated to contain 22 IgE binding components [3]. However, only Per a 1, Per a 3 (aryl- phorin-hemocyanin), Per a 6 (troponin C), Per a 7 (tropomyosin), Per a 9 (arginine kinase) and Per a 10 (serine protease) have been isolated and characterized as major allergens [4–7]. Serine proteases from house dust mite (Der p 3, Der p 6, Der p 9, Der f 3, Der f 6), Aspergillus fumigatus (Asp f 13), Penicillium species (Pen c 1, Pen ch 13, Pen o 18), Epicoccum purpurascens (Epi p 1) and Curvularia lunata (Cur l 1) were identified as major allergens [8–15]. Proteolytically active allergens act on the airway by cleaving tight junction proteins thereby increasing epithelial permeability and release of pro- inflammatory cytokines through the activation of