Grass immunotherapy induces inhibition of allergen-specific human peripheral blood mononuclear cell proliferation

Production of T-cell lines

Allergen-specific T-cell lines established from allergic patients provide the opportunity of investigating T-cell functions at the poly- or oligoclonal level. T-cell lines are useful in determining the presence or absence of antigen-specific T-cell reactivity. However, to obtain detailed knowledge of the action of T cells with clearly defined features, for example epitope specificity or phenotype, T-cell clones are necessary.The frequency of allergen-specific T cells in peripheral blood mononuclear cells (PBMC) tends to be low and so stimulation of PBMC with single allergens often results in low allergen-specific reactivity or requires high doses of the allergen. In contrast, the stimulation of PBMC with whole allergen extract results in stronger reactivity because a greater spectrum of T-cell specificities is addressed. Therefore, for the investigation of polyclonal reactivity toward single allergens it is useful to establish T-cell lines, which represent an allergen-specific enrichment of T cells from the respective individual. These T cells are poly- or oligoclonal and might possess different epitope specificities. The method described here is based on experiences with human T-cell lines and clones specific for several allergens from grass pollens and tree pollens.

The role of mast cells in atopy: what can we learn from canine models? A thorough review of the biology of mast cells in canine and human systems

Mast cell research has largely focused on the role of these cells in the early phase of allergic reactions. However, their involvement may well extend beyond this stage, and even reach across nonallergic conditions. Mast cells from different sources have helped advance our knowledge of their biology. Although in vitro and in vivo research in this area has mainly focused on humans, such studies are limited by the extent to which cells from certain human tissues and/or human patients can be collected or studied. While rodents also provide valuable models with which to further our understanding of the behaviour of mast cells and their contribution to allergy, reported differences between human and murine mast cells, and, in some instances, the limitations of in vivo rodent models of mast cell-mediated allergic conditions, preclude their use. In this review, we introduce a relatively unknown mast cell population, that of the dog. Canine mast cells display many phenotypic and functional similarities with their human counterparts, and dogs develop spontaneous and induced allergic diseases that share clinical and pathophysiological features with the human condition. Therefore, the use of canine cells can shed light on the general role of mast cells, particularly in relation to allergic diseases given the potential of in vivo dog models within this field. Here we provide a detailed review of the data reported from in vitro and in vivo studies of canine mast cells, and compare them with results obtained in human systems. We also highlight direct evidence of the mast cell contribution to canine atopy. We conclude that the dog offers useful in vitro and in vivo models in which to investigate mast cell behaviour, and that its use should be considered when undertaking studies aimed either at elucidating the role of mast cells in health and disease, or at prescreening novel therapies prior to entry into man.

Production of interleukin-12 by monocytes and interferon-gamma by natural killer cells in allergic patients during rush immunotherapy

BACKGROUND

Allergen specific immunotherapy modifies the immunologic response to allergen exposure; however, the role of cells composing the innate immune system, such as monocytes and natural killer (NK) cells, in this mechanism is still unclear.

OBJECTIVE

To examine the effect of rush immunotherapy (RIT) on early allergen-induced cytokine production by peripheral blood mononuclear cells from treated cat- and birch-allergic patients.

METHODS

Twelve allergic patients received RIT, and another 4 served as controls. Blood samples were taken before the start and after 3 days, 1 week, 3 weeks, and 3 months of RIT. Allergen-induced production of interleukin-12 (IL-12) by monocytes and interferon-gamma (IFN-gamma) by NK cells was evaluated by means of flow cytometry.

RESULTS

Before the start of RIT, allergic patients had significantly lower numbers of IL-12+ monocytes compared with healthy subjects (P = .01). The percentage of IL-12+ monocytes increased after 3 months of RIT (P = .003). In the allergic control group, the proportion of IL-12+ monocytes evaluated after 3 months was not different from baseline and was significantly lower compared with that in the RIT group (P = .005). Before treatment, the percentage of IFN-gamma+ NK cells was lower in allergic patients than in healthy subjects (P = .04). The percentage of IFN-gamma+ NK cells increased after 3 weeks (P = .03) and 3 months (P = .01) of RIT.

CONCLUSIONS

Restoration of the cytokine imbalance by immunotherapy is not only restricted to the cells of the adaptive immune system but also concerns cells composing the innate immune system.

Age-related T cell responses to allergens in childhood

BACKGROUND

T cell priming, as determined by allergen-induced proliferative responses, is believed to occur principally in early childhood in both atopic and non-atopic infants under the influence of multiple factors including environmental allergen exposure. It is considered that T cell priming with expansion of Th2 cells is a crucial factor in the development of atopic disease.

OBJECTIVE

To examine T cell priming to commonly encountered allergens in childhood in relation to age.

METHODS

In a cross-sectional study T cell proliferation in relation to age was examined for three common allergens, ovalbumin (OVA), house dust mite (HDM) and rye grass pollen (RYE), in atopic and non-atopic children. The effect of age on Th1 (IFN-gamma) and Th2 (IL-5 and IL-13) cytokine production in response to these allergens was investigated to examine the possibility of immune deviation with time.

RESULTS

A significant increase in T cell proliferation with age was observed with RYE among atopic children only. However, the same was not observed with the two other allergens studied (i.e. OVA and HDM). In addition, RYE-induced (but not HDM or OVA) cytokine production showed an increased Th2 deviation with age as reflected in the increasing IL-5/IFN-gamma and IL-13/IFN-gamma ratios only among the atopic subjects with rye grass pollen sensitivity.

CONCLUSION

These findings suggest that grass pollen sensitivity in childhood is accompanied by a progressive accumulation of allergen-primed T cells and progressive deviation of the allergen-induced cytokine response towards a Th2 response in atopic subjects throughout childhood.

Development of new IgE specificities to allergenic components in birch pollen extract during specific immunotherapy studied with immunoblotting and Pharmacia CAP System

BACKGROUND

New IgE sensitizations to proteins in allergen extracts have been shown to occur during allergen-specific immunotherapy (IT). However little is known about the kinetics of the changes in antibody reactivities.

METHODS

Twenty-four allergic children and adults were treated with birch pollen rush IT (RIT). Fifteen matched patients served as allergic controls. Sera were obtained at regular intervals for up to three years and analyzed with immunoblotting and Pharmacia CAP System with recombinant (r) birch pollen allergens (rBet v 1, rBet v 2, and rBet v 4).

RESULTS

All birch-allergic patients had specific IgE to the major birch pollen allergen Bet v 1, but only three had IgE to rBet v 2 and/or rBet v 4 at the beginning of the study. New IgE sensitizations developed in 65% of the birch RIT-treated patients when studied by immunoblotting. Twenty-nine percent of the patients developed new sensitizations to rBet v 2 and/or rBet v 4 during RIT as measured by Pharmacia CAP System. Generally, new specific IgE reactivities occurred after at least one year of RIT, and only at low levels (< 1 kUA/l).

CONCLUSIONS

Sensitization to additional allergenic pollen components frequently occurs during prolonged birch RIT. However, the IgE levels are low and the clinical relevance is not known.

Specific immunotherapy prevents increased levels of allergen-specific IL-4- and IL-13-producing cells during pollen season

BACKGROUND

Specific allergen immunotherapy (SIT) is effective for treatment of IgE-mediated diseases: however, the mechanisms of action still remain unclear. Earlier, we showed that IL-4 and IL-13 are produced in response to specific allergens. The aim of this study was to investigate whether these cytokine responses were affected by allergen SIT, and, furthermore, to evaluate the effect of SIT on allergen-specific IgE and IgG4 levels.

METHODS

Blood samples from pollen-sensitized individuals were collected before the pollen season (before treatment) and during the pollen season (after SIT or placebo treatment). Peripheral blood mononuclear cells were activated in vitro with allergens and the numbers of IL-4-, IL-13-, IL-10-, and IFN-gamma-producing cells were determined by ELISPOT. Serum levels of allergen-specific IgE and IgG4 were measured by RAST and ELISA, respectively.

RESULTS

The numbers of IL-4- and IL-13-producing cells were shown to be increased in the placebo group during the pollen season, an increment which was absent in patients receiving allergen SIT. We found an increase in allergen-specific IgG4 in the SIT-treated individuals, but not in the placebo group. Both groups displayed elevated specific IgE levels during the pollen season.

CONCLUSIONS

Taken together, our data show a downregulation of IL-4- and IL-13-producing cells in peripheral blood after SIT, suggesting induction of nonresponsiveness/tolerance or a redistribution of these cells. Furthermore, we demonstrate that SIT acts on antibody production by increasing the specific IgG4 levels.

Changes in cytokine production in vitro during the early phase of birch-pollen immunotherapy

The kinetics of the immunological mechanisms during allergen-specific immunotherapy (IT) has not been thoroughly evaluated. In this investigation we study the changes in T-cell responses during the early phase of IT. Ten patients (IT group) with birch-pollen allergy were treated with conventional IT. Blood samples were collected at regular intervals for specific immunoglobulin (Ig)E measurements and preparation of peripheral blood mononuclear cells (PBMC). Seven allergic control patients (AC group) were included during the subsequent birch-pollen season. The PBMC were stimulated with birch-pollen extract or tetanus toxoid (TT) and mitogens. After a short decrease, probably owing to seasonal variation, the birch-pollen-specific proliferation and the interleukin (IL)-4, IL-5, and IL-10 production significantly increased when reaching the maintenance dose and during the subsequent pollen season. The increase in IL-4 correlated with a temporary increased serum level of birch-pollen-specific IgE. Interestingly, also the TT-specific response was affected by IT, resulting in weaker, but in time similar, changes in proliferation and cytokine production as in the birch-pollen-specific response. We speculate that the early phase of IT might lead to systemic changes in the capacity of Th2-like cytokine production, and that the early increase in allergen-specific IgE is a consequence of enhanced IL-4 production.

Cytokine production by peripheral blood mononuclear cells following birch-pollen immunotherapy

We studied the Th2/Th1 balance by short-term stimulation of peripheral blood mononuclear cells (PBMC) isolated during the pollen season from seven allergic patients treated with conventional birch-pollen immunotherapy (IT) for 18 months, eight matched allergic control patients and 10 non-atopic individuals. The PBMC were cultured for 7 days with birch-pollen extract (BPE) or tetanus toxoid (TT), and then restimulated with PHA and PMA to induce high IL-5, IL-10 and IFN-gamma production. The serum levels of birch-pollen-specific IgG and IgG4 were significantly elevated after IT treatment. The proliferative response to BPE was significantly enhanced in the allergic control group, but not in the IT-treated group, compared to the non-atopic group (P<0.05). Birch-pollen-specific IL-5 production was significantly enhanced in both the IT-treated group and the allergic control group (P<0.01-0. 05). Furthermore, both the IT-treated group and the allergic control group had a cytokine profile to BPE significantly more Th2 polarized (high IL-5/IFN-gamma ratio) than to TT (P<0.05 and P<0.01, respectively). No differences in IL-10 production between the three study groups were observed. The Th2/Th1 balance in vitro correlated with the serum concentrations of birch-pollen-specific IgE (r=0.60, P<0.05), and in the IT-treated group, also with the IgG and IgG4 levels (r=0.79, P<0.05 and r=0.86, P<0.05, respectively). We conclude that conventional birch-pollen IT does not lead to changes in the cytokine profile of the circulating pool of allergen-specific T cells during birch-pollen season. However, induction of peripheral T-cell tolerance and increased production of specific IgG and IgG4 might be part of the mechanisms of IT.

Study of the Th1/Th2 balance, including IL-10 production, in cultures of peripheral blood mononuclear cells from birch-pollen-allergic patients

BACKGROUND

Excessive production of interleukin (IL)-4, IL-5, IL-10, and IL-13 is thought to be important in the development of allergy and asthma. The objective of this investigation was to study Th1/Th2-like cytokine profiles in vitro in seven patients allergic to birch pollen and six nonallergic controls during the birch-pollen season.

METHODS

Peripheral blood mononuclear cells (PBMC) were isolated and cultured with birch-pollen extract (BPE) or tetanus toxoid (TT) for 7 days, harvested, and restimulated with the mitogens phytohemagglutinin (PHA) and phorbol 12-myristate 13-acetate (PMA) for 24 h. Cytokine production was determined by ELISA, and logarithmic cytokine ratios were compared between the two groups and between the antigens.

RESULTS

In the allergic group, the cultures prestimulated with BPE had a more Th2-like cytokine response than the TT-prestimulated cultures; i.e., lower IFN-gamma and higher IL-10 production (P<0.05), as well as higher IL-5/IFN-gamma and IL-13/ IFN-gamma ratios (P<0.05). There were also significantly higher IL-4/IFN-gamma (P<0.005) and IL-5/IFN-gamma (P<0.05) ratios in BPE-stimulated cultures in the allergic group than in the control group. The IL-4 and IL-13 production in vitro correlated with the specific serum IgE levels.

CONCLUSIONS

BPE stimulation induces a Th2-like cytokine response by PBMC isolated during the pollen season from birch-pollen-allergic patients, indicating a Th2-type immune response to birch pollen in vivo.