Background Macrophage inflammatory protein (MIP)-1α binds to C–C chemokine receptor (CCR)-1 with high affinity. CCR-1 is expressed on neutrophils, eosinophils, monocytes, T lymphocytes and basophils; cells characteristic of atopic allergic inflammation. In vitro, MIP-1α is chemotactic for monocytes, T cells and basophils and is also a potent histamine-releasing factor for basophils and mast cells. Although increased levels of MIP-1α were shown in atopic allergic disorders, the kinetics of expression of these CC chemokines in vivo is largely unknown.
Objective To investigate the kinetics of expression of MIP-1α and receptor CCR-1 and the relationships between the expression and infiltration of inflammatory cells in allergen-induced cutaneous late-phase reactions in atopic subjects.
Methods Cryostat sections, obtained from skin biopsies from 10 human atopic subjects at 6, 24, 48, 72 h and 7 days after allergen challenge, were processed for immunohistochemistry and in situ hybridization using 35S-labelled riboprobes.
Results The peak expression of allergen-induced mRNA for MIP-1α and CCR-1 was 6 h. This was maintained at 24 h, and gradually returned to base line at 7 days. At 6 h, the number of cells expressing MIP-1α mRNA significantly correlated with elastase+ neutrophils and BB-1+ basophils. At 24 h, the MIP-1α mRNA+ cells significantly correlated with CD68+ macrophages. There were significant inverse correlations between the numbers of MIP-1α mRNA cells and the numbers of Tryptase+ mast cells at 6 and 24 h after allergen challenge.
Conclusion Allergen-induced cutaneous late-phase reactions in humans were associated with increased expression of MIP-1α and CCR-1. This may be relevant to the infiltration of neutrophils, eosinophils, basophils and macrophages.
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