The allergy adjuvant effect of particles - genetic factors influence antibody and cytokine responses

Abstract

Background: There is increasing epidemiological and experimental evidence for an aggravating effect of particulate air pollution on asthma and allergic symptoms and, to a lesser extent, on allergic sensitization. Genetic factors appear to influence not only the magnitude, but also the quality of the adjuvant effect of particles with respect to allergen-specific IgE (Th2-associated) and IgG2a (Th1-associated) responses. In the present study, we aimed to investigate how the genetic background influences the responses to the allergen and particles alone and in combination. We examined how polystyrene particles (PSP) affected the IgE and IgG2a responses against the model allergen ovalbumin (OVA), after subcutaneous injection into the footpad of BALB/cA, BALB/cJ, NIH and C3H/HeN mice, Further, ex vivo IL-4, IFN-gamma and IL-10 cytokine secretion by Con A-stimulated cells from the draining popliteal lymph node (PLN) five days after injection of OVA and PSP separately or in combination was determined.

Results: PSP injected with OVA increased the levels of OVA-specific IgE antibodies in all strains examined. In contrast, the IgG2a levels were significantly increased only in NIH and C3H/HeN mice. PSP in the presence of OVA increased cell numbers and IL-4, IL-10 and IFN-gamma levels in BALB/cA, NIH and C3H/HeN mice, with the exception of IFN-gamma in NIH mice. However, each mouse strain had their unique pattern of response to OVA+PSP, OVA and PSP, and also their unique background cytokine response (i.e. the cytokine response in cells from mice injected with buffer only).

Conclusion: Genetic factors (i.e. the strain of mice) influenced the susceptibility to the adjuvant effect of PSP on both secondary antibody responses and primary cellular responses in the lymph node, as well as the cellular responses to both OVA and PSP given separately. Interestingly, PSP alone induced cytokine responses in the lymph node in some of the mouse strains. Furthermore, we found that the ex vivo cytokine patterns did not predict the in vivo Th2- and Th1-associated antibody response patterns in the different mouse strains. The results indicate that insoluble particles act by increasing the inherent response to the allergen, and that the genetic background may determine whether an additional Th1-associated component is added to the response.

Figure 1

Allergen and particle dose-response experiments in BALB/cA and NIH mice Levels of serum OVA-specific IgE (A, D), IgG1 (B, E) and IgG2a (C, F) on day 26 after injection into one hind footpad of 100 (open columns), 50 (gray) or 10 (black) μg OVA combined with 100, 40, 10 or 0 μg PSP, or buffer (HBSS (hatched)), in BALB/cA (A, B, C) and NIH (D, E, F) mice. On day 21 the mice were boostered with the same OVA dose in the footpad. The PSP-control ("PSP ctr") group was given 100 μg PSP on day 0, followed by HBSS injection on day 21 (diamonds). Values (arbitrary units, AU) for individual mice (circles) and median values (columns) for groups of eight mice are shown. Dotted lines indicate the lower or higher detection limits for the ELISA assays. Note different scales for the two strains of mice.

Figure 2

The adjuvant effect of PSP on OVA-specific IgE and IgG2a responses in different strains of mice Levels of serum OVA-specific IgE (A) and IgG2a (B) on day 26 after injection into one hind footpad of HBSS (open columns), 10 μg OVA (gray), 40 μg PSP (hatched) or 10 μg OVA + 40 μg PSP (black) in different mouse strains. On day 21 all mice were boostered with 10 μg OVA in the footpad. Vertical straight lines indicate separate experiments. Values (arbitrary units, AU) for individual mice (circles) and median values (columns) for groups of mice are shown. Dotted lines indicate the lower detection limits for the ELISA assays. Brackets indicate statistically significant differences between groups (p < 0.05). All experiments were performed twice with similar results, with eight mice per group.

Figure 3

The primary cellular response in the draining lymph node The primary cellular response in the draining PLN was determined five days after a single injection of HBSS (open columns), 10 μg OVA (gray), 40 μg PSP (hatched) or 10 μg OVA + 40 μg PSP (black) into both hind footpads of BALB/cA, NIH and C3H/HeN mice. The total lymph node cell numbers (A) and IL-4 (B), IFN-γ (C) and IL-10 (D) secreted from the PLN cells after ex vivo stimulation with Con A were determined. Values for individual samples (circles) and group median values (columns) are shown. Dotted lines indicate the lower detection limits for the cytokine ELISA assays, and brackets indicate statistically significant differences between groups (p < 0.05).