Recirculation of lymphocytes: its role in implementing immune responses in the skin

A number of recent investigations have suggested that the subset of lymphocytes which migrate into nonlymphoid tissue to appear in peripheral lymph may be partly different from the major recirculating pool migrating through lymphoid tissues. We report results on the migrating from the blood of thoracic duct lymphocytes labelled with Cr and three subsets-accredited recirculators, activated lymphocytes and long-lived lymphocytes. The localization of these populations was studied in normal skin, in a contact sensitivity lesion and in a site of non-immune inflammation. All four populations localized in the contact sensitivity lesion in increased numbers compared to normal skin but long-lived lymphocytes appeared to discriminate between cell-mediated immunity and non-immune inflammation; activated lymphocytes migrated most efficiently into the non-immune inflammatory site (Table 4).