Preferential recruitment of activated, memory T lymphocytes into skin chamber fluids during human cutaneous late-phase allergic reactions

To determine whether activated memory T lymphocytes (CD3⁺ CD4⁺ CD45RO⁺ CD25⁺ HLA-DR⁺) preferentially accumulate during the cutaneous IgE-dependent late-phase response, we challenged 10 atopic patients with allergen and monitored the cellular influx for 12 hours with a skin blister chamber model. Four patients with allergy were also challenged with irrelevant allergen in control experiments. Histamine release and the size of the cutaneous late-phase response were measured. Light microscopic analysis and phenotyping of recruited and blood lymphocytes were performed with immunofluorescence and flow cytometry. Antigen challenge induced significant histamine release, a macroscopic late-phase response, and significant cellular influx in the appropriately challenged patients with allergy but not in control subjects. In the control group, only limited phenotypic analyses could be performed, which demonstrated an equivalent percentage of CD3⁺ CD4⁺ cells in the chamber fluids compared with blood. In contrast, a higher proportion of CD4⁺ T lymphocytes and a lower proportion of CD8⁺ T lymphocytes accumulated in chamber fluids during the late-phase response compared with that present in blood. The vast majority of the recruited T lymphocytes expressed a memory phenotype (CD45RO⁺) with enhanced percentages of CD25⁺ and HLA-DR⁺ cells. Also, these cells had increased levels of very late antigen-4 (CD49d/CD29) and reduced levels of L-selectin compared with the same cells in blood. These results demonstrate that allergen challenge of the skin in patients with allergy leads to the preferential accumulation of activated, memory T lymphocytes. The mechanism by which these cells are selectively recruited during cutaneous allergic inflammation remains to be determined. (J Allergy Clin Immunol 1995;96:57-65.).