The binding of antigen presenting cells to T lymphocytes.
In the introduction, we asked how MHC molecules on the surfaces of APC make contact with antigen-specific receptors on the surfaces of T cells. We have reviewed two models in which antigen-specific contacts occur with primary leukocyte populations in vitro. One system involves resting T cells; the other sensitized T lymphoblasts. At the onset of a primary immune response, dendritic cells seem critical for binding and activating both CD4+ and CD8+ subsets. Given the current evidence, we suggest that dendritic cells literally find the right T cell clone, and not vice versa, and that dendritic cells do so by first binding and surveying T cells by an antigen-independent mechanism. In the efferent limb of immunity, other types of APC including B cells and macrophages bind and stimulate freshly sensitized T lymphoblasts. Freshly isolated epidermal Langerhans cells do not cluster T cells by an antigen-independent mechanism but acquire this capacity during epidermal suspension culture. Under the control of GM-CSF, the Langerhans cell becomes a powerful accessory cell for the primary or sensitization limb of T-dependent immune responses like the MLR and primary antibody response. Isolated lymphoid dendritic cells have many features in common with interdigitating cells in lymphoid T areas, and may be related to some of the irregularly-shaped Ia+ cells in certain epithelia and interstitial regions. Contact with dendritic cells may be important in both central and peripheral pathways of T cell sensitization in situ.
Steinman
R M
RM
Rockefeller University, N.Y., N.Y. 10021.
Inaba
K
K
D000818:Animals; D000911:Antibodies, Monoclonal; D000937:Antigen-Antibody Reactions; D000938:Antigen-Presenting Cells / Q000502:physiology*; D000954:Antigens, Surface / Q000502:physiology; D001402:B-Lymphocytes / Q000502:physiology; D002448:Cell Adhesion; D002450:Cell Communication; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007801:Langerhans Cells / Q000502:physiology; D008264:Macrophages / Q000502:physiology; D013601:T-Lymphocytes / Q000502:physiology*
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface