# Hapten-Specific Cellular Immune Responses in the Elicitation and Sensitization Phases of Murine Contact Hypersensitivity

## TL;DR

This study examines immune responses in mice during two phases of contact hypersensitivity, revealing differences in reactions to different haptens.

## Contribution

The study provides new insights into hapten-specific immune responses during sensitization and elicitation phases of CHS.

## Key findings

- First exposure to DNFB caused more pronounced ear swelling and neutrophil infiltration compared to TNCB.
- Repeated TNCB exposure increased edema and T cell accumulation, while repeated DNFB did not significantly aggravate edema.
- Both haptens induced hapten-specific immune responses during sensitization and elicitation phases.

## Abstract

Contact dermatitis (CD) is a common inflammatory skin condition with irritant etiology or a delayed-type hypersensitivity called allergic contact dermatitis (ACD). Contact hypersensitivity (CHS) is a widely used rodent model of ACD and similarly consists of two phases: sensitization and elicitation. To trigger CHS, low-molecular-weight haptens, such as DNFB or TNCB, are commonly applied. However, the characterization of the induced immune response remains incomplete. Our aim was to characterize the immune response after first and repeated exposures to model haptens. First exposure to DNFB or TNCB led to significant ear swelling, with DNFB causing a more pronounced effect. DNFB enhanced neutrophil infiltration, whereas TNCB led to macrophage, dendritic cell, and helper T cell accumulation. Repeated DNFB exposure did not aggravate edema significantly, while TNCB re-exposure enhanced edema formation and induced neutrophil granulocyte, dendritic cell, and helper and cytotoxic T cell accumulation. Our results demonstrate that a hapten-specific immune response is induced during both phases of CHS. A detailed understanding of allergen-specific immune responses is crucial for the appropriate selection of the model and for gaining deeper insight into the mechanisms of inflammatory skin diseases. These findings may contribute to the targeted selection of haptens.