Drug-induced exanthems.

Area of Science:

• Immunology
• Dermatology
• Pharmacology

Background:

• Cutaneous adverse drug reactions present diverse clinical and histopathological features.
• Drug-reactive T cells are increasingly recognized as key players in these reactions.
• Understanding T cell functions offers insight into the spectrum of drug eruptions.

Purpose of the Study:

• To elucidate the distinct T cell functions underlying different cutaneous drug reactions.
• To differentiate the roles of CD4+ and CD8+ T cells in maculopapular versus bullous drug eruptions.
• To investigate the contribution of specific cytokines and chemokines to drug-induced exanthems.

Main Methods:

• Immunohistological analysis of skin biopsies from patients with drug reactions.
• Functional studies of drug-specific T cells.
• Analysis of cytokine and chemokine profiles (e.g., IL-5, eotaxin).

Main Results:

• Drug-specific CD4+ T cells expressing cytotoxic proteins (perforin, granzyme B) are implicated in maculopapular exanthems, targeting keratinocytes.
• These CD4+ T cells accumulate at the dermo-epidermal junction, causing basal keratinocyte damage.
• Preferential activation of drug-specific cytotoxic CD8+ T cells may drive more severe bullous drug eruptions.
• Distinct cytokine profiles, including upregulation of IL-5 and eotaxin in maculopapular exanthems, correlate with observed eosinophilia.

Conclusions:

• Distinct T cell subsets and their functional activities are critical in determining the clinical presentation of cutaneous drug reactions.
• CD4+ cytotoxic T cells contribute to keratinocyte apoptosis in maculopapular drug eruptions.
• CD8+ cytotoxic T cells may mediate severe blistering reactions.
• Cytokine profiles, such as IL-5 and eotaxin, help explain specific features like eosinophilia in certain drug eruptions.