Accessory cell-T lymphocyte interactions. Antigen-dependent and -independent clustering.

Abstract

Previous work documented the capacity of dendritic cells (DC) to stimulate primary immune responses and to physically cluster with the responding lymphocytes. Rapid cell-cell aggregation assays were used here to study the interaction of DC and other types of APC with T lymphocytes. Graded doses of APC were sedimented with T cells that had been primed to alloantigens, soluble proteins, or lectin, and then labeled with carboxyfluorescein diacetate. The number of clustered T cells was measured after 10 min at 4 or 37 degrees C. At 4 degrees, binding was antigen-dependent and included greater than 50% of the added T cells. Clustering was mediated by all types of APC tested, including DC, macrophages, B lymphocytes, and fresh Langerhans cells, although DC were the most effective. Specificity was evident in the findings that alloreactive T lymphoblasts bound to allogeneic but not syngeneic APC; KLH- and OVA-reactive T cells bound to syngeneic APC in the presence of specific protein: and Con A blasts needed lectin to cluster. A 30 min pretreatment with chloroquine, a drug known to inhibit APC activity, markedly blocked the specific binding of alloreactive and protein-specific T blasts at 4 degrees C. Since Lyt-2- alloreactive blasts should specifically recognize Ia, presentation of Ia seems to be altered by chloroquine. Binding assays at 37 degrees C gave similar results to those performed at 4 degrees C, with one exception. When DC were used as APC, striking antigen-independent clustering occurred. DC could efficiently cluster primed T cells in the absence of alloantigen, soluble protein, or lectin. We suggest that antigen-independent binding contributes to the distinctive capacity of DC to prime T cells in the afferent limb of the immune response, whereas antigen-dependent binding between other APC and sensitized lymphocytes is critical in the efferent limb.

Migration patterns of dendritic cells in the mouse. Traffic from the blood, and T cell-dependent and -independent entry to lymphoid tissues.

“…Thus migration of DC from the blood to the spleen is regulated by T cells. Although we initially thought that this might be due to direct DC-T cell clustering, analogous to that studied in vitro (30) and implicated in vivo (38), elsewhere we present evidence that is contrary to this idea (17). In particular, we have found that the DC are initially localized within the red pulp of the spleen but that later, and only after a period of what appears to be active migration, they enter the white pulp.…”

Interleukin 1 enhances T-dependent immune responses by amplifying the function of dendritic cells.

“…Memory T cells were prepared by resting the blasts for three or more days in the absence of exogenous IL-2 or alloantigen (19) . The blasts and memory populations were >70% allospecific, as assessed in rapid DC-T binding assays (28 Mixtures of accessory-cell depleted B and T lymphocytes were obtained by passing spleen suspensions over Sephadex G10 (17) . 4 X 10 lymphocytes were cultured in 16-mm-diam wells for 4 d with antigen (2 X 106 SRBC; or 10,ug/ml TNP-KLH) and graded doses of DC (17).…”

Comparison of the Accessory Activity of Murine Peritoneal Cavity Macrophage Derived Dendritic Cells and Peritoneal Cavity Macrophages in a Mixed Lymphocyte Reaction.

“…They are the principal stimulators of primary immune responses [13,26,35,38,39]. In studies of lymphoid DC as potent stimulators of the MLR in mice, Steinman and Whitmer [7] showed that a ratio of just one DC to 50-250 T cells induced a maximal reaction. Wong et al [42] demonstrated that DC were reproducibly the most potent stimulators of T cell responses on a per cell basis when compared with macrophages even when higher levels of MHC molecules were induced on the surface of macrophages with IFN-γ [36].…”

“…Dendritic cells (DC) are efficient stimulators of both allogeneic and syngeneic mixed lymphocyte reaction, MLR [7]. They are the principal stimulators of primary immune responses [13,26,35,38,39].…”