IntroductionDrug Reaction with Eosinophilia Systemic Symptoms (DRESS) is more common in persons living with HIV (PLHIV), and first-line anti-TB drugs (FLTDs) and cotrimoxazole are the commonest offending drugs. Limited data is available on the skin infiltrating T-cell profile among DRESS patients with systemic CD4 T-cell depletion associated with HIV.Materials and methodsHIV cases with validated DRESS phenotypes (possible, probable, or definite) and confirmed reactions to either one or multiple FLTDs and/or cotrimoxazole were chosen (n= 14). These cases were matched against controls of HIV-negative patients who developed DRESS (n= 5). Immunohistochemistry assays were carried out with the following antibodies: CD3, CD4, CD8, CD45RO and FoxP3. Positive cells were normalized to the number of CD3+ cells present.ResultsSkin infiltrating T-cells were mainly found in the dermis. Dermal and epidermal CD4+ T-cells (and CD4+/CD8+ ratios) were lower in HIV-positive vs. negative DRESS;p< 0.001 andp= 0.004, respectively; without correlation to whole blood CD4 cell counts. In contrast, no difference in dermal CD4+FoxP3+ T-cells was found in HIV-positive vs. negative DRESS, median (IQR) CD4+FoxP3+ T-cells: [10 (0–30) cells/mm2vs. 4 (3–8) cells/mm2,p= 0.325]. HIV-positive DRESS patients reacting to more than one drug had no difference in CD8+ T-cell infiltrates, but higher epidermal and dermal CD4+FoxP3+ T-cell infiltrates compared to single drug reactors.ConclusionDRESS, irrespective of HIV status, was associated with an increased skin infiltration of CD8+ T-cells, while CD4+ T-cells were lower in HIV-positive DRESS compared to HIV-negative DRESS skin. While inter-individual variation was high, the frequency of dermal CD4+FoxP3+ T-cells was higher in HIV-positive DRESS cases reacting to more than one drug. Further research is warranted to understand the clinical impact of these changes.