Trimellitic anhydride-induced cellular infiltration into guinea pig lung varies with age but not gender

Background: In humans the incidence of asthma changes with age and gender. Immature guinea pigs have been used to model the allergic response to the occupational allergen trimellitic anhydride (TMA) where exposure to adults is paramount. We hypothesized that the TMA-induced allergic response in immature guinea pigs was similar to mature animals, regardless of gender. Methods: Sexually immature and mature female and male guinea pigs were sensitized intradermally with TMA. Three weeks after sensitization they were challenged intratracheally with TMA conjugated to guinea pig serum albumin (TMA-GPSA) or GPSA as a control. Twenty-four hours later cell infiltration into the lung was determined. TMA-specific IgG₁ and IgG₂ were measured in plasma and the complement activation product C3a was measured in the bronchoalveolar lavage fluid. Results: In control animals, numbers of eosinophils and neutrophils varied with age and gender. The TMA-GPSA-induced cellular infiltration was similar in all age/gender groups. However, neutrophils in the lung tissue increased only in immature animals. IgG antibodies differed between groups but did not account for differences in cell infiltration. C3a correlated with the extent of cell infiltration in all groups except mature females. Conclusions: TMA-induced neutrophilia differs with age. TMA-induced changes in eosinophils and macrophages did not vary with age or gender. The relationship between complement activation and inflammation in mature females differs from that in the other groups, suggesting mediators of the response may change with age and gender. Effects of age and gender need to be considered in animal models of the allergic response.