Allergic Effector Research Articles

Migration of helper T-lymphocyte subsets into inflamed tissues

The localization of lymphocytes to specific tissues is a finely regulated event that has key implications in the development of chronic allergic inflammation that is associated with allergic rhinitis, atopic dermatitis, and asthma. Key players in the tissue localization of lymphocytes and other allergic effector cells include cellular adhesion molecules and chemokines. The expression or activation pattern of these proinflammatory mediators appears to depend, in part, on the local cytokine milieu. For instance, the TH1 phenotype is associated with the upregulation of intercellular adhesion molecule-1 and RANTES, whereas the TH2 phenotype is associated with the upregulation of vascular cell adhesion molecule and P-selectin. Notably, the recruitment of certain cell populations, such as eosinophils (hallmark of chronic allergic inflammation), into inflamed tissue sites is dependent on the preferential expression of adhesion molecules, chemokines, and associated receptors. The potential mechanisms that underlie cell migration into inflamed tissue as currently understood are reviewed. (J Allergy Clin Immunol 2000;106:S264-9.)

The 18-kDa form of cat allergen Felis domesticus 1 (Fel d 1) is associated with gelatin- and fibronectin-degrading activity.

Fel d 1, an important allergen from domestic cats, is a significant cause of asthma. In addition to directly promoting IgE synthesis, other biological activities of allergens may contribute to either allergic sensitization or the magnitude of allergic effector responses. For example, allergens that degrade proteins have been suggested to facilitate allergen presentation by increasing parallelular permeability of airways epithelium. However, little information exists to indicate whether Fel d 1 has other activities relevant to allergic responses. To study whether Fel d 1 is associated with enzyme activity. Fel d 1 was obtained by a rigorous purification strategy and its identity confirmed by laser desorption mass spectrometry, cleavage and sequencing. The ability of Fel d 1 to degrade gelatin, fibronectin and the artificial substrate N-benzoyl-FVR-p-nitroanilide was studied. The effect of Fel d 1 on the morphology of tight junctions in epithelial cell monolayers was also investigated. The 18-kDa form of Fel d 1 caused degradation of denatured collagens (gelatin) and cleaved a 20-kDa fragment from the A chain of plasma fibronectin. Catalytic activity was not altered by inhibitors of cysteine peptidases, matrix metallopeptidases or by removal of divalent cations. In contrast, aprotinin and TLCK were inhibitors of Fel d 1. The absence of a serine peptidase catalytic triad in Fel d 1, together with the stoichiometry of the inhibition of TLCK and aprotinin, suggest that their inhibitory action may be due to noncatalytic site interactions. Alternatively, highly purified Fel d 1 may be associated with an active contaminant, although none were found. These results suggest that Fel d 1 is another example of a domestic allergen which is associated with enzyme activity. It remains to be established whether the activity resides in Fel d 1 itself or in an unresolved, and possibly related, protein.

Mechanisms of allergen-specific immunotherapy.

Mechanisms of allergen-specific immunotherapy.

In vitro investigations with the histamine H1 receptor antagonist, epinastine (WAL 801 CL), on isolated human allergic effector cells.

Skin mast cells, basophils and eosinophils are effector cells of acute and subacute allergic responses due to their capacity to produce a large number of (pro)inflammatory mediators. Histamine H1 receptor antagonists, such as epinastine (WAL 801 CL), have been described to partially exert antiallergic and antiinflammatory effects both in vivo and in vitro in addition to their antihistaminergic properties. The aim of the present study was to investigate whether epinastine could influence the in vitro activation of isolated human skin mast cells, basophils and eosinophils induced by different secretagogues. Cells were isolated from healthy women following plastic surgery and healthy blood donors, respectively. Mast cells were isolated by enzymatic digestion of the skin. Blood cells were isolated by gradient centrifugation and negative selection with magnetic beads. A wide range of concentrations of the drug (1 nmol/l to 100 micromol/l) did not significantly inhibit histamine release from basophils induced by immunologic (anti-IgE, concanavalin A, priming factors interleukin-3 and interleukin-5) and non immunologic (A23187, ionomycin, 12-o-tetradecanoyl-phorbol-13-acetate, C5a, formyl-methionyl-leucyl-phenylalanine) stimuli. Furthermore, the drug had no effect on A23187-induced release of eosinophil cationic protein from eosinophils. However, at a concentration >0.1 nmol/l, IgE-mediated LTC4 production from basophils was significantly suppressed. Histamine release from skin mast cells due to anti-IgE or A23187 was inhibited by epinastine in a dose-dependent fashion, whereas substance P-induced activation as well as stem cell factor priming were not. Epinastine did not inhibit isolated protein kinase C from rat brain. The results confirm previous in vivo and in vitro observations obtained from animal models that epinastine exerts antiallergic and antiinflammatory effects. Whether the observed effects are due to non specific membrane interactions or by influencing intracellular signal transduction elements has to be further elucidated.

An in vitro Model for the Allergen–IgE–FcεRI Interaction

Background: The interaction of immune complexes consisting of allergens and allergen–specific IgE with the high–affinity Fcε receptor represents the key event in the induction of symptoms in type I allergic individuals. Immediate–type symptoms result from the release of biological mediators due to allergen–induced cross–linking of FcεRI receptors on mast cells and basophils, whereas FcεRI–mediated presentation of allergen–IgE complexes may contribute to late–phase symptoms through enhanced T cell activation. The interaction of allergens/allergen–specific IgE/FcεRI represents, therefore, an important target for therapeutic intervention strategies in type I allergy. Methods and Results: A molecular model of the allergen–IgE–FcεRI interaction was established. It consists of recombinant purified Bet v 1, the major birch pollen allergen, a chimeric Bet v 1 specific monoclonal IgE antibody, and the baculovirus–expressed purified human alpha chain of FcεRI. The chimeric Bet v 1–specific IgE antibody consists of the light chain and the heavy chain variable region of a mouse monoclonal Bet v 1 specific antibody, Bip 1, and the constant region of human IgE. The interaction of rBet v 1, chimeric Bip 1, and human alpha chain was investigated by overlay experiments. Nitrocellulose–immobilized recombinant alpha chains was incubated with chimeric Bip 1 and, for control purposes, with mouse–derived Bip 1. Bound chimeric Bip 1 was detected with ¹²⁵I–labeled rBet v 1. The specific interaction of rBetv 1, chimeric Bip 1, and recombinant human alpha chain is demonstrated. We thus establish a molecular model of the allergen/IgE/alpha chain interaction. The usefulness of the described in vitro system is exemplified by the identification of a mouse monoclonal antihuman IgE antibody which blocked the IgE–alpha chain interaction. Conclusions: The module system consisting of rBet v 1, chimeric Bip 1, and recombinant alpha chain may be used for the identification of competitors of the allergic effector reaction by means of high throughput screening of compounds or by combinatorial chemistry.

The murine homolog of TB2/DP1, a gene of the familial adenomatous polyposis (FAP) locus

The cDNA of the murine counterpart of the human TB2/DP1 (deleted in polyposis) gene, one of the six genes deleted in severe cases of familial adenomatous polyposis (FAP) disease, was isolated and analyzed. The murine transcript is 734-bp long and thereby considerably shorter than the 3100-bp human counterpart. This is due to a completely different 3' untranslated region in mouse which starts immediately after the translational stop codon, thereby deleting a RFLP (restriction-fragment length polymorphism) marker for this disease. The amino acid sequence, however, is 92% conserved between mouse and man. Triggering of murine mast cells by IgE plus antigen results in a decrease of TB2/DP1 mRNA up to 60% after 2 h implying a possible role of this gene in regulation of the allergic effector cell. Reverse transcription-polymerase chain reaction (RT-PCR) analysis shows an ubiquitous expression pattern in a number of mouse cell lines and tissues

Isolation of an immunodominant IgE hapten from an epitope expression cDNA library. Dissection of the allergic effector reaction.

An epitope expression cDNA library was constructed from the randomly fragmented cDNA coding for Phl p I, the major grass pollen allergen. Using IgE from allergic patients, epitope clones were isolated and immunodominant fragments were selected. Among three epitope clones coding for a similar region of Phl p I, one clone expressed a 15-amino-acid epitope which was target for IgE antibodies from approximately 30% of grass pollen allergic patients. According to the prevalence of grass pollen allergy, 22% of all allergic patients are expected to display IgE reactivity with this epitope. Although the purified recombinant epitope specifically bound IgE, it did not release histamine from basophiles of most grass pollen allergic patients and thus represents an IgE hapten. Immunodominant IgE haptens may be useful as therapeutic agents to saturate mast cell-bound IgE prior to allergen exposure and may represent candidates for a safe immunotherapy of allergic diseases by reducing anaphylactic side effects.

Type β Transforming Growth Factors Promote Interleukin-3 (IL-3)-Dependent Differentiation of Human Basophils But Inhibit IL-3-Dependent Differentiation of Human Eosinophils

Basophils and eosinophils share a common differentiation pathway. Factors regulating terminal commitment toward one cell type, however, have so far not been defined. Interleukin-3 (IL-3) is a potent differentiation factor for both human eosinophils and basophils. In the present study, the effects of various recombinant human (rh) growth regulators on IL-3-dependent growth of eosinophils and basophils were studied in a bone marrow (BM) suspension culture system (normal donors, n = 13). We found that type beta transforming growth factors (TGFs) lead to a significant increase in the absolute numbers of basophils in BM cultures grown in the presence of IL-3 (day 14 of culture; IL-3: 133 +/- 20 v IL-3 + TGF-beta 1: 231 +/- 28 x 10(3)/mL [P less than .01]) and to an increase in the total histamine values (IL-3: 72.6 +/- 22.2 v IL-3 + TGF-beta 1: 142.9 +/- 37.3 ng/mL [P less than .015]) compared with rhIL-3 alone. In contrast, type beta TGFs were found to inhibit the IL-3-dependent growth of eosinophils (IL-3: 170.4 +/- 37.2 v IL-3 + TGF-beta 1: 16.7 +/- 5.2 x 10(3)/mL [P less than .01]) and formation of eosinophil cationic protein in the same culture system. The effect of TGF-beta 1 (and TGF-beta 2) on IL-3-dependent differentiation of basophils and eosinophils was dose- and time-dependent (maximum effects observed with 1 to 10 ng/mL of rhTGF-beta 1 or TGF-beta 2) and could be neutralized by an antibody specific for TGF-beta 1. In contrast to the TGFs, interferon-alpha (IFN-alpha) and IFN-gamma were found to downregulate IL-3-dependent formation of both basophils (IL-3: 167 +/- 33 v IL-3 + IFN-alpha: 67 +/- 25 v IL-3 + IFN-gamma: 65 +/- 33 x 10(3)/mL [P less than .01]) and eosinophils (IL-3: 239 +/- 5 v IL-3 + IFN-alpha: 81 +/- 4 v IL-3 + IFN-gamma: 67 +/- 17 x 10(3)/mL [P less than .05]) in our culture system. Type beta TGFs as well as the IFNs failed to directly induce differentiation of human basophils or eosinophils in the absence of other growth factors. Together, these results show that type beta TGFs and IFNs are potent regulators of cytokine-dependent growth and differentiation of human allergic effector cells.

Type beta transforming growth factors promote interleukin-3 (IL-3)- dependent differentiation of human basophils but inhibit IL-3-dependent differentiation of human eosinophils

Basophils and eosinophils share a common differentiation pathway. Factors regulating terminal commitment toward one cell type, however, have so far not been defined. Interleukin-3 (IL-3) is a potent differentiation factor for both human eosinophils and basophils. In the present study, the effects of various recombinant human (rh) growth regulators on IL-3-dependent growth of eosinophils and basophils were studied in a bone marrow (BM) suspension culture system (normal donors, n = 13). We found that type beta transforming growth factors (TGFs) lead to a significant increase in the absolute numbers of basophils in BM cultures grown in the presence of IL-3 (day 14 of culture; IL-3: 133 +/- 20 v IL-3 + TGF-beta 1: 231 +/- 28 x 10(3)/mL [P less than .01]) and to an increase in the total histamine values (IL-3: 72.6 +/- 22.2 v IL-3 + TGF-beta 1: 142.9 +/- 37.3 ng/mL [P less than .015]) compared with rhIL-3 alone. In contrast, type beta TGFs were found to inhibit the IL-3-dependent growth of eosinophils (IL-3: 170.4 +/- 37.2 v IL-3 + TGF-beta 1: 16.7 +/- 5.2 x 10(3)/mL [P less than .01]) and formation of eosinophil cationic protein in the same culture system. The effect of TGF-beta 1 (and TGF-beta 2) on IL-3-dependent differentiation of basophils and eosinophils was dose- and time-dependent (maximum effects observed with 1 to 10 ng/mL of rhTGF-beta 1 or TGF-beta 2) and could be neutralized by an antibody specific for TGF-beta 1. In contrast to the TGFs, interferon-alpha (IFN-alpha) and IFN-gamma were found to downregulate IL-3-dependent formation of both basophils (IL-3: 167 +/- 33 v IL-3 + IFN-alpha: 67 +/- 25 v IL-3 + IFN-gamma: 65 +/- 33 x 10(3)/mL [P less than .01]) and eosinophils (IL-3: 239 +/- 5 v IL-3 + IFN-alpha: 81 +/- 4 v IL-3 + IFN-gamma: 67 +/- 17 x 10(3)/mL [P less than .05]) in our culture system. Type beta TGFs as well as the IFNs failed to directly induce differentiation of human basophils or eosinophils in the absence of other growth factors. Together, these results show that type beta TGFs and IFNs are potent regulators of cytokine-dependent growth and differentiation of human allergic effector cells.

Suppressor cells of popliteal lymph node origin are involved in thein vivo andin vitro control of experimental allergic encephalomyelitis effector cells in the Lewis rat

Lewis rats immunized in the hind footpads with total guinea pig spinal cord tissue in mycobacteria-enriched complete Freund's adjuvant develop chronic relapsing experimental allergic encephalomyelitis. It was previously shown that popliteal lymph node cells (LNC) isolated at the time of the first recovery (day 16) and transferred into naive syngeneic recipients protect from active induction of the disease. On the other hand, inguinal LNC taken at the onset of the disease (day 11) induce under similar conditions an acceleration of the appearance of the clinical symptoms. In this report, we show that the in vivo suppressive activity of popliteal LNC is associated with the absence of production of interleukin 2 in this compartment. The lack of production of this lymphokine and the suppressive activity can be detected only in the popliteal compartment and appear as early as day 11 after immunization. We show that this suppressive population displays in vitro inhibitory activity on the proliferative response of the disease effectors (inguinal LNC) to guinea pig myelin basic protein. This suppressive activity is not abrogated by addition of interleukin 2, suggesting that these suppressor cells do not inhibit the proliferation by absorption of the released lymphokine or by inhibition of its production.