Identification of IL-8 as a locomotor attractant for activated human lymphocytes in mononuclear cell cultures with anti-CD3 or purified protein derivative of Mycobacterium tuberculosis.

On culture of human blood mononuclear cells for 24 to 48 h with anti-CD3 (aCD3) or purified protein derivative of Mycobacterium tuberculosis, chemoattractants are released into the medium which induce polarization and locomotion of activated (G1) lymphocytes but not resting lymphocytes. Here we show that, during a period of up to 72 h of culture, IL-8 is released in nanomolar quantities into the supernatant and that the lymphocyte chemoattractant activity of these supernatants is inhibited by incubation with anti-IL-8. Examination of the cultured mononuclear cells by immunofluorescence suggests that many monocytes, but almost no lymphocytes in aCD3 cultures contain IL-8 in cytoplasmic organelles, yet few monocytes direct from blood stained for IL-8. IL-8 is an attractant for only a small proportion (ca 10%) of lymphocytes direct from blood. The proportion of responding cells is increased after culture for 24 to 48 h in aCD3 or purified protein derivative of Mycobacterium tuberculosis, and these are a phenotypically distinct subpopulation consisting of large lymphocytes enriched for CD45RO. These cells respond to their own culture supernatants and to IL-8 in polarization assays and by invasion of collagen gels into which the attractants are incorporated. They also show orientation to a source of IL-8 in a chemotactic gradient. These responses are consistent with in vivo observations that the lymphocytes which migrate selectively into inflammatory sites are activated. The fact that many lymphocytes do not respond to IL-8 may reflect the diversity of migratory pathways shown by lymphocytes in vivo, the locomotion of small, recirculating, lymphocytes being regulated by other, unknown, locomotor stimuli.