- Email: [email protected]
Current knowledge on molecular structure of allergens
REVUEFRANCAISE D'ALLERGOL~)GIE ETDqMMUNOLOGIECIINIQUE
Current knowledge on molecular structure of allergens B. DAVID
INTRODUCTION
An allergen is an antigen when it provokes, on a first contact, specific IgE synthesis and, later, anaphylactic or inflammatory reactions for an allergic patient. In a healthy population, the same molecule will behave as a classical antigen without any allergic disorders [1]. The regulation of IgE synthesis depends of cytokines released by T lymphocytes. Th2 profile cells produce, Interleukin-4 (IL-4) and Interleukin 13 (IL-13) which promote IgE synthesis by B cells, whereas T h l cells produce IFN- which prevent hypersensitivity by playing a negative regulatory role in the development of Th2 cells. As it is well-established, the hypersensitivity reactions are genetically controlled, but they are also d e p e n d e n t on n u m e r o u s factors [2, 3]. A m o n g them, the structure of allergenic molecules has been evoked suggesting that it could exist a relationship between biochemical properties of allergens and their immunogenicity [4]. Biochemical activities of allergens
Many studies on some allergenic molecules revealed that half of t h e m either possess a biochemical activity or were t h o u g h t to be biochemically active, according to sequence
homologies. Although the second half of these characterized allergens do not show significant h o m o l o g y with o t h e r known proteins, the possibility of an unknown biochemical activity cannot be excluded. Regarding the known or supposed biochemical functions of allergens, we can arbitrarily divided them into two broad groups : the enzymes and the binding proteins. THE ENZYMES
T h e enzymes are classified on the basis of the reactions they catalyze. There are six major classes: Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, and Ligases and the majority of the allergens are hydrolytic enzymes, including Esterases and Proteases. Esterases
The most of allergens having esterase activity are described a m o n g the hymenoptera enzymes. Indeed, Phospholipase A1 and A2 represent major allergens present in the venom of various species of hymenoptera :Apis mellifera (Api m 1), Dolichovespula maculata (Dol m 1), Polistes annularis (Pol a 1), Vespula matulifrons (vesm 1), Vespula vulgaris (ves v 1) and Vespa crabro (vesp c
])
[5].
DAVID B. - Current knowledge on molecular structure of allergens. Rev. fr. Allergol., 1999, (Num6ro special), 2-5.
Unit6 d'Immuno-Allergie, Institut Pasteur, PARIS. © Expansion Scientifique Publications, 1999
/ CURRENT KNOWLEDGE OAr MOLECULAR STRUCTURE OF ALLERGENS •
In IgE mediated hypersensibility reactions to the bee venom, 90% of patients have serum IgE antibodies against phospholipase A2 E6, 7]. The interest in phospholipase A2 (PLA2) comes from the fact that it constitutes a major allergen from bee venom called Api m 1 and from the fact that it has an enzymatic activity with a cytotoxic effect. The study of t h e interactions between PLA2 and the m e m b r a n e surface of cells such as RBL (Rat Basophilic Leukemia) has revealed a specific cytotoxic activity of the enzyme in the absence of antibodies [8]. Dudler et al. have analysed the mechanism of action of PLA2 on m e m b r a n e phospholipids at the all m e m b r a n e and have proposed a theoric concept about its allergenicity relating the enzymatic activity to the synthesis of specific IgE [9]. Thus, They have demonstrated histamin, 5hydroxytryptamin and hexosaminidase release as well as some TH2 cytokins by RBL cells following incubation of PLA2 with m e m b r a n e phospholipids. In the same time, they have showed that a simple mutation of the active enzymatic site of PLA2 abolishes m e m b r a n e alterations as well as inflammatory mediator release in the absence of IgE antibodies. However, no difference IgEmediated mast cell degranulation with active and inactive enzymes have been found and up to now enzymatically active PLA2 in specific IgE synthesis has not been demonstrated, yet. Proteases Allergens from various sources have now been recognized as expressing proteolytic activity (table I). Among the house dust mite allergens at least four of them are proteinases (Groups 1, 3, 6, and 9). If we consider only group 1 mite allergens, major allergens of D e r m a t o p h a g o i d e s Pteronyssinus (Der p 1), D. Farinae (Der f 1), D. microceras (Der m 1) and Euroglyphus manei (Eur m 1) are cysteine proteases that belong to the papain family of enzymes, together with other allergens of plant origin: Gly m l (soybean), chymopapain (papaya fruit), actinidin (kiwi fruit), bromelain, and ananain (pineapple). This family of proteases displays closely related amino acid sequences and uses an identical catalytic group, the thiolate imidazolium pair, for their activity. A comparative modeling study of Der p 1, has shown that this protein shares amazing structural and mechanistic features with papain and actinidin [10]. Rev.fr. AllergoL,
1999,Nurntrospdcial
Fig 1. - Modeldepictingthat the enzymaticacnvityofDer p 1 can take place in varioussteps and have differenttargets during the sensitizationprocess.
Several direct or indirect links have already been described between cysteine proteinase activity of Der p 1 and its immunogeniticy leading to four ways (fig. 1). Disruption of cohesion in the epithelial barrier Herbert et al. have reported some experiments that suggest that Der p 1 is capable of causing the bronchial epithelium to b e c o m e increasingly permeable to macromolecules, such as albumin, as a consequence of proteolytic injury. They s h o m e d that exposure of isolated bronchial segments to Der p 1 resulted in disruption of epithelial architecture that can be visualized by histological techniques [ 11]. Inactivation of natural protective molecules Der p 1 has also been shown to catalytically inactivate ~I-antitrypsin, a serine-proteinase inhibitor that protects the h u m a n lower respiratory tract against damage by proteinases released during inflammation and therefore, what exacerbate tissue damage and inflammation, thus accentuating asthma [12]. IgE-independent stimulation of mediator release from mast ceils Machado et al. have reported that enzymatically active Der p 1 was able to induce, by a noncytotoxic mechanism, mast cell and basophil degranulation and to stimulate IL-4 synthesis and secretion in the absence of antigen-specific IgE. In contrast, no histamine or IL-4 release was d e t e c t e d after challenge with enzymatically inactive Der p 1 [15].
• B. DAVID /
Disruption of IgE network Recently, two i n d e p e n d e n t reports demonstrated that Der p 1 may upregulate lgE synthesis by virtue of its ability to cleave the low-affinity IgE Fc receptor (CD23) from the surface of cultured h u m a n B cells. The cleavage of this CD23 may deprive the B cell of an important mechanism to limit IgE synthesis a n d generate soluble fragments of CD23 that directly enhance IgE synthesis. Furthermore, the proteolytic effect of Der p 1 was specific for CD23, since no other B-cell markers tested were affected [14, 15]. THE BINDING PROTEINS According to sequence homology a large panel of allergens thought to display binding activity (table II) whose lipocalins are the most representative. T h e lipocalins and the fatty acid-binding proteins are two protein families that b o t h function by binding small h y d r o p h o b i c molecules. Their similarities of structure and sequence suggest that they form part of a larger structural superfamily that has been called the calycins to reflect the cup-shaped structures of its members. Several allergens have been shown to belong to this kind of binding [ 16]. Recently we identified' and purified in our laboratory a major horse allergen, Equ c 1 that elicits an IgE-mediated type I allergic reaction. The gene encoding this allergen was cloned from total cDNA of sublingual salivary gland by RT-PCR
and a recombinant form expressed in Escherichia coli [17]. The complete sequence amino acid and its tertiary structure after cristallographic analysis revealed that Equ c 1 is a new m e m b e r of the lipocalin superfamily, [18] known to include several allergens as Mus m 1 (mouse), Rat n 1 and Rat n 2 (Rat), Bos d 2 (bovin danders), Can f 1 and Can f 2 (dog), Bla g 4 (cockroach) and Asc s 1 (worm). Although the folding architecture of lipocalins is appropriate for binding and transport of small hydrophobic molecules as retinoids an steroid hormones, well known for regulatory signaling molecules for cell growth [19], there is no evidence to prove their possible influence on IgE synthesis. CONCLUSIONS Up until now, it was not clear whether allergenassociated biochemical potencies like profilin and tropomyosin actin-binding, cation-binding, or even ribonuclease activities may influence immunogenicity and allergenicity. Although the link between biochemical properties of some molecules and their aptitude to trigger IgE responses is well-documented, there is now no available rule that allows to draw a general concept. However, it is likely that the biochemical actions of allergen can take place in various steps of i m m u n e response or inflammatory process, independently of IgE synthesis, but amplifying and perpetuating the pathology of the allergic mecanisms.
REFERENCES 1. David B,, Boitard C. - Maladies atlergiques par hypersensibilit6 imm6diate, allerg&nes et environnement. M6decine th6rapeutique, 1996, 2, n°6, 411-419. 2. David B. - G6n6tique et atopie. M6decine thfirapeutique, 1996, 2, n°6, 421-424. 3. David B. - De la synth~se des immunoglobulines E aux syndromes allergiques. La Revue du Praticien, 1996, 46, 935-941. 4. Musu T., Gr6goire C., David B., Dandeu J.P, - The relationships between the biochemical properties of allergens and their immunogenicity. Clin. Rev. All. Immunol., 1997, 15, 485-498. 5. King T.R, Hoffman D., Lowenstein H., Marsh D.G., Platts-Mills T.A., Thomas W. - Allergen nomenclature. Allergy Sep., 1995, 50 (9), 765-774. 6. Kemeny D.M., MacKenzie-Mills M., Harries M.G., Youlten LJ., Lessor M.H. - Antibodies to purified bee venom proteins and peptides. II: A detailed study of changes in IgE and IgG antibodies to individual bee venom antigens. J. Allergy Clin. Immnnol., 1983, 72, 376-385. 7. Kemeny D.M., Harries M.C., Youlten L.J., MacKenzie-Mills M., Lessof M.H. - Antibodies to purified bee venom proteins and peptides. I. development of a highly specific PAST for bee venom antigens and its application to bee sting allergy. J. Allergy Clin. Immunol., 1983, 71,505-514,
8. Helm B.A. - Is there a link between the nature of agents that trigger mast cells and the induction of immunoglobulin (Ig) E synthesis? Adv. Exp. Med. Biol., 1994, 347, 1-10. 9. Dudler T., Machado D.C., Kolbe L., Annand R.R., Rhodes N., Gelb M.H., Koelsch K., Surer M., Helm B.A. - A link between catalytic activity, IgE-independent mast cell activation, and allergenicity of bee venom phospholipase A2. J. Immunol., 1995, 155, 2605-2613. 10. Topham C.M., Srinivasan N., Thorpe c.j., Overington J.P., Kalsheker N.A. - Comparative modelling of major house dust mite allergen der p 1: structure validation using an extended environmental amino acid propensity table. Protein Eng., '19941 7, 869-894. 11. Herbert C.A., King C.M., Ring RC,, Holgate S.T., Stewart G.A., Thompson PJ, Robinson C. - Augmentation of permeability in the bronchial epithelium by the house dust mite allergen Der p 1. Am.J. Respir. Cell Mol. Biol.~ 1995, 12, 369-378, 12. Kalsheker N.A., Deam S., Chambers L., Sreedharan S., Brocklehurst K., Lomas D.A. - The house dust mite ailergen Der p 1 catalytically inactivates alpha 1-antitr)]osin by specific reactive centre loop cleavage: a m e c h a n i s m that promotes airway inflammation and asthma. Biochem. Biophys. Res. Commun., 1996, 221, 59-61. Rev. Jh. Allergol., 1999, Numdro spdcial
/ CURRENT KNOWLEJ)GE ON MOLECULAR STRUCTURE OF ALLERGENS * 13. Machado D.C., Horton D., Harrop R., Peachell P.T., Helm B.A. Potential allergens stimulate the release of mediators of the allergic response from cells of the mast cell lineage in the absence of sensitization with antigen-specific IgE. Eur. J. Immunol., 1996, 26, 2972-2980. 14. Schulz O., Lalng P., Sewell H.F., Skakib F. - Der p 1, a major allergen of the house dust mite, proteolytically cleaves the lowaffinity receptor for human IgE (CD23). Eur. J. Immunol., 1995, 25, 3191-3194. 15. Hewitt C.R., Brown A.E, Hart B.J., pritchard D,!. - A major house dust mite allergen disrupts the immunogl0bulin E network by selectively cleaving CD23: innate protection by antiproteases. J. Exp. Med., 1995, 182, 153%1544. 16. Flower D.R. - The lipocalin protein family: a role in cell regulation. FEBS Lett., 1994, 354, 7-11.
mmm
Rev.fr. Allergol., 1999, Num6ro sp6cial
17. Gr~goire C., Rosinski-Chupin I., RabillonJ., Alzari P.M., David B., Dandeu J.E - cDNA Cloning and Sequencing Reveal the Major Horse Allergen Equ c 1 to Be a Glycoprotein Member of the lipocalin Superfamily. J. Biol. Chem., 1996. 271, n°51, 3295132959. 18. Grfigoire C., Tavares G.A., Lorenzo H.K~, Dandeu J.E, David B., Alzari P.M. - crystallization and preliminary cristallographic analysis of the major horse allergen Equ c 1. Acta Cristallogr. D, 1999, 55, 880-882. 19. Gudas LJ. - Retinoids and vertebrate development. Journal of Biological Chemistry., 1994, 269, 15399-15402. 20. x x x c. - Augmentation of permeability in the bronchial epithelium by the house dust mite allergen Der p. 1995.
Current knowledge on molecular structure of allergens B. DAVID
INTRODUCTION
An allergen is an antigen when it provokes, on a first contact, specific IgE synthesis and, later, anaphylactic or inflammatory reactions for an allergic patient. In a healthy population, the same molecule will behave as a classical antigen without any allergic disorders [1]. The regulation of IgE synthesis depends of cytokines released by T lymphocytes. Th2 profile cells produce, Interleukin-4 (IL-4) and Interleukin 13 (IL-13) which promote IgE synthesis by B cells, whereas T h l cells produce IFN- which prevent hypersensitivity by playing a negative regulatory role in the development of Th2 cells. As it is well-established, the hypersensitivity reactions are genetically controlled, but they are also d e p e n d e n t on n u m e r o u s factors [2, 3]. A m o n g them, the structure of allergenic molecules has been evoked suggesting that it could exist a relationship between biochemical properties of allergens and their immunogenicity [4]. Biochemical activities of allergens
Many studies on some allergenic molecules revealed that half of t h e m either possess a biochemical activity or were t h o u g h t to be biochemically active, according to sequence
homologies. Although the second half of these characterized allergens do not show significant h o m o l o g y with o t h e r known proteins, the possibility of an unknown biochemical activity cannot be excluded. Regarding the known or supposed biochemical functions of allergens, we can arbitrarily divided them into two broad groups : the enzymes and the binding proteins. THE ENZYMES
T h e enzymes are classified on the basis of the reactions they catalyze. There are six major classes: Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, and Ligases and the majority of the allergens are hydrolytic enzymes, including Esterases and Proteases. Esterases
The most of allergens having esterase activity are described a m o n g the hymenoptera enzymes. Indeed, Phospholipase A1 and A2 represent major allergens present in the venom of various species of hymenoptera :Apis mellifera (Api m 1), Dolichovespula maculata (Dol m 1), Polistes annularis (Pol a 1), Vespula matulifrons (vesm 1), Vespula vulgaris (ves v 1) and Vespa crabro (vesp c
])
[5].
DAVID B. - Current knowledge on molecular structure of allergens. Rev. fr. Allergol., 1999, (Num6ro special), 2-5.
Unit6 d'Immuno-Allergie, Institut Pasteur, PARIS. © Expansion Scientifique Publications, 1999
/ CURRENT KNOWLEDGE OAr MOLECULAR STRUCTURE OF ALLERGENS •
In IgE mediated hypersensibility reactions to the bee venom, 90% of patients have serum IgE antibodies against phospholipase A2 E6, 7]. The interest in phospholipase A2 (PLA2) comes from the fact that it constitutes a major allergen from bee venom called Api m 1 and from the fact that it has an enzymatic activity with a cytotoxic effect. The study of t h e interactions between PLA2 and the m e m b r a n e surface of cells such as RBL (Rat Basophilic Leukemia) has revealed a specific cytotoxic activity of the enzyme in the absence of antibodies [8]. Dudler et al. have analysed the mechanism of action of PLA2 on m e m b r a n e phospholipids at the all m e m b r a n e and have proposed a theoric concept about its allergenicity relating the enzymatic activity to the synthesis of specific IgE [9]. Thus, They have demonstrated histamin, 5hydroxytryptamin and hexosaminidase release as well as some TH2 cytokins by RBL cells following incubation of PLA2 with m e m b r a n e phospholipids. In the same time, they have showed that a simple mutation of the active enzymatic site of PLA2 abolishes m e m b r a n e alterations as well as inflammatory mediator release in the absence of IgE antibodies. However, no difference IgEmediated mast cell degranulation with active and inactive enzymes have been found and up to now enzymatically active PLA2 in specific IgE synthesis has not been demonstrated, yet. Proteases Allergens from various sources have now been recognized as expressing proteolytic activity (table I). Among the house dust mite allergens at least four of them are proteinases (Groups 1, 3, 6, and 9). If we consider only group 1 mite allergens, major allergens of D e r m a t o p h a g o i d e s Pteronyssinus (Der p 1), D. Farinae (Der f 1), D. microceras (Der m 1) and Euroglyphus manei (Eur m 1) are cysteine proteases that belong to the papain family of enzymes, together with other allergens of plant origin: Gly m l (soybean), chymopapain (papaya fruit), actinidin (kiwi fruit), bromelain, and ananain (pineapple). This family of proteases displays closely related amino acid sequences and uses an identical catalytic group, the thiolate imidazolium pair, for their activity. A comparative modeling study of Der p 1, has shown that this protein shares amazing structural and mechanistic features with papain and actinidin [10]. Rev.fr. AllergoL,
1999,Nurntrospdcial
Fig 1. - Modeldepictingthat the enzymaticacnvityofDer p 1 can take place in varioussteps and have differenttargets during the sensitizationprocess.
Several direct or indirect links have already been described between cysteine proteinase activity of Der p 1 and its immunogeniticy leading to four ways (fig. 1). Disruption of cohesion in the epithelial barrier Herbert et al. have reported some experiments that suggest that Der p 1 is capable of causing the bronchial epithelium to b e c o m e increasingly permeable to macromolecules, such as albumin, as a consequence of proteolytic injury. They s h o m e d that exposure of isolated bronchial segments to Der p 1 resulted in disruption of epithelial architecture that can be visualized by histological techniques [ 11]. Inactivation of natural protective molecules Der p 1 has also been shown to catalytically inactivate ~I-antitrypsin, a serine-proteinase inhibitor that protects the h u m a n lower respiratory tract against damage by proteinases released during inflammation and therefore, what exacerbate tissue damage and inflammation, thus accentuating asthma [12]. IgE-independent stimulation of mediator release from mast ceils Machado et al. have reported that enzymatically active Der p 1 was able to induce, by a noncytotoxic mechanism, mast cell and basophil degranulation and to stimulate IL-4 synthesis and secretion in the absence of antigen-specific IgE. In contrast, no histamine or IL-4 release was d e t e c t e d after challenge with enzymatically inactive Der p 1 [15].
• B. DAVID /
Disruption of IgE network Recently, two i n d e p e n d e n t reports demonstrated that Der p 1 may upregulate lgE synthesis by virtue of its ability to cleave the low-affinity IgE Fc receptor (CD23) from the surface of cultured h u m a n B cells. The cleavage of this CD23 may deprive the B cell of an important mechanism to limit IgE synthesis a n d generate soluble fragments of CD23 that directly enhance IgE synthesis. Furthermore, the proteolytic effect of Der p 1 was specific for CD23, since no other B-cell markers tested were affected [14, 15]. THE BINDING PROTEINS According to sequence homology a large panel of allergens thought to display binding activity (table II) whose lipocalins are the most representative. T h e lipocalins and the fatty acid-binding proteins are two protein families that b o t h function by binding small h y d r o p h o b i c molecules. Their similarities of structure and sequence suggest that they form part of a larger structural superfamily that has been called the calycins to reflect the cup-shaped structures of its members. Several allergens have been shown to belong to this kind of binding [ 16]. Recently we identified' and purified in our laboratory a major horse allergen, Equ c 1 that elicits an IgE-mediated type I allergic reaction. The gene encoding this allergen was cloned from total cDNA of sublingual salivary gland by RT-PCR
and a recombinant form expressed in Escherichia coli [17]. The complete sequence amino acid and its tertiary structure after cristallographic analysis revealed that Equ c 1 is a new m e m b e r of the lipocalin superfamily, [18] known to include several allergens as Mus m 1 (mouse), Rat n 1 and Rat n 2 (Rat), Bos d 2 (bovin danders), Can f 1 and Can f 2 (dog), Bla g 4 (cockroach) and Asc s 1 (worm). Although the folding architecture of lipocalins is appropriate for binding and transport of small hydrophobic molecules as retinoids an steroid hormones, well known for regulatory signaling molecules for cell growth [19], there is no evidence to prove their possible influence on IgE synthesis. CONCLUSIONS Up until now, it was not clear whether allergenassociated biochemical potencies like profilin and tropomyosin actin-binding, cation-binding, or even ribonuclease activities may influence immunogenicity and allergenicity. Although the link between biochemical properties of some molecules and their aptitude to trigger IgE responses is well-documented, there is now no available rule that allows to draw a general concept. However, it is likely that the biochemical actions of allergen can take place in various steps of i m m u n e response or inflammatory process, independently of IgE synthesis, but amplifying and perpetuating the pathology of the allergic mecanisms.
REFERENCES 1. David B,, Boitard C. - Maladies atlergiques par hypersensibilit6 imm6diate, allerg&nes et environnement. M6decine th6rapeutique, 1996, 2, n°6, 411-419. 2. David B. - G6n6tique et atopie. M6decine thfirapeutique, 1996, 2, n°6, 421-424. 3. David B. - De la synth~se des immunoglobulines E aux syndromes allergiques. La Revue du Praticien, 1996, 46, 935-941. 4. Musu T., Gr6goire C., David B., Dandeu J.P, - The relationships between the biochemical properties of allergens and their immunogenicity. Clin. Rev. All. Immunol., 1997, 15, 485-498. 5. King T.R, Hoffman D., Lowenstein H., Marsh D.G., Platts-Mills T.A., Thomas W. - Allergen nomenclature. Allergy Sep., 1995, 50 (9), 765-774. 6. Kemeny D.M., MacKenzie-Mills M., Harries M.G., Youlten LJ., Lessor M.H. - Antibodies to purified bee venom proteins and peptides. II: A detailed study of changes in IgE and IgG antibodies to individual bee venom antigens. J. Allergy Clin. Immnnol., 1983, 72, 376-385. 7. Kemeny D.M., Harries M.C., Youlten L.J., MacKenzie-Mills M., Lessof M.H. - Antibodies to purified bee venom proteins and peptides. I. development of a highly specific PAST for bee venom antigens and its application to bee sting allergy. J. Allergy Clin. Immunol., 1983, 71,505-514,
8. Helm B.A. - Is there a link between the nature of agents that trigger mast cells and the induction of immunoglobulin (Ig) E synthesis? Adv. Exp. Med. Biol., 1994, 347, 1-10. 9. Dudler T., Machado D.C., Kolbe L., Annand R.R., Rhodes N., Gelb M.H., Koelsch K., Surer M., Helm B.A. - A link between catalytic activity, IgE-independent mast cell activation, and allergenicity of bee venom phospholipase A2. J. Immunol., 1995, 155, 2605-2613. 10. Topham C.M., Srinivasan N., Thorpe c.j., Overington J.P., Kalsheker N.A. - Comparative modelling of major house dust mite allergen der p 1: structure validation using an extended environmental amino acid propensity table. Protein Eng., '19941 7, 869-894. 11. Herbert C.A., King C.M., Ring RC,, Holgate S.T., Stewart G.A., Thompson PJ, Robinson C. - Augmentation of permeability in the bronchial epithelium by the house dust mite allergen Der p 1. Am.J. Respir. Cell Mol. Biol.~ 1995, 12, 369-378, 12. Kalsheker N.A., Deam S., Chambers L., Sreedharan S., Brocklehurst K., Lomas D.A. - The house dust mite ailergen Der p 1 catalytically inactivates alpha 1-antitr)]osin by specific reactive centre loop cleavage: a m e c h a n i s m that promotes airway inflammation and asthma. Biochem. Biophys. Res. Commun., 1996, 221, 59-61. Rev. Jh. Allergol., 1999, Numdro spdcial
/ CURRENT KNOWLEJ)GE ON MOLECULAR STRUCTURE OF ALLERGENS * 13. Machado D.C., Horton D., Harrop R., Peachell P.T., Helm B.A. Potential allergens stimulate the release of mediators of the allergic response from cells of the mast cell lineage in the absence of sensitization with antigen-specific IgE. Eur. J. Immunol., 1996, 26, 2972-2980. 14. Schulz O., Lalng P., Sewell H.F., Skakib F. - Der p 1, a major allergen of the house dust mite, proteolytically cleaves the lowaffinity receptor for human IgE (CD23). Eur. J. Immunol., 1995, 25, 3191-3194. 15. Hewitt C.R., Brown A.E, Hart B.J., pritchard D,!. - A major house dust mite allergen disrupts the immunogl0bulin E network by selectively cleaving CD23: innate protection by antiproteases. J. Exp. Med., 1995, 182, 153%1544. 16. Flower D.R. - The lipocalin protein family: a role in cell regulation. FEBS Lett., 1994, 354, 7-11.
mmm
Rev.fr. Allergol., 1999, Num6ro sp6cial
17. Gr~goire C., Rosinski-Chupin I., RabillonJ., Alzari P.M., David B., Dandeu J.E - cDNA Cloning and Sequencing Reveal the Major Horse Allergen Equ c 1 to Be a Glycoprotein Member of the lipocalin Superfamily. J. Biol. Chem., 1996. 271, n°51, 3295132959. 18. Grfigoire C., Tavares G.A., Lorenzo H.K~, Dandeu J.E, David B., Alzari P.M. - crystallization and preliminary cristallographic analysis of the major horse allergen Equ c 1. Acta Cristallogr. D, 1999, 55, 880-882. 19. Gudas LJ. - Retinoids and vertebrate development. Journal of Biological Chemistry., 1994, 269, 15399-15402. 20. x x x c. - Augmentation of permeability in the bronchial epithelium by the house dust mite allergen Der p. 1995.