Macrophage-T lymphocyte relationships in man's contact allergic reactions.

Seventeen biopsies from contact allergic reaction sites in sensitized patients were studied by electron microscopy and immunocytochemistry. Very intimate appositions of macrophages to T lymphocytes were frequently observed in the dermis at 6, 8 and 12 hours after application of the allergen. Such juxtapositions were seen less frequently after 24, 48 and 72 hours. These appositions seem to indicate that macrophages play an antigen-presenting role in human contact allergic reactions, as Langerhans cells seem to do.