Role of veiled cells in lymphocyte activation

Abstract

Peripheral blood lymphocytes from normal rabbits or from rabbits hyperimmunized with human immunoglobulin were cultured in 20-microliters hanging droplets. The cultures were stimulated with concanavalin A or, in the case of cells from sensitized animals, with human immunoglobulin. The addition to the cultures of small numbers of autologous or allogeneic veiled cells separated from afferent lymph increased the responses to low doses of the stimulants, particularly when the cells were cultured at low cell densities or for short periods of time. At high cell densities or at longer periods of culture, stimulation occurred in the absence of added veiled cells and was associated with clumping of the lymphoid cells and development of cells which morphologically resembled veiled cells found in afferent lymph. The enhanced responses upon addition of small numbers of veiled cells were also correlated with the formation of lymphoid aggregates which were frequently held together by the elongated processes of a single veiled cell. The observations support the view that the veiled cells are lymph-borne precursors of dendritic cells in the lymph nodes. This may provide an in vitro model for the cellular relationships which occur in paracortical cords of lymph nodes following antigenic stimulation.

Induction of immune responses in vivo with small numbers of veiled (dendritic) cells.

“…The reduction in the yield of low density cells from spleens and lymph nodes of animals with EAE might indicate a change in the distribution of VC in this disease. However, confirmation of this change in sections of lymph nodes must be sought because VC can clump with lymphocytes on stimulation with antigen (5). This could lead to loss of the VC in these clumps in the density gradient separation.…”

“…Veiled or dendritic cells (VC), the interdigitating cells within T-cell areas of lymph nodes or spleen, or their putative precursors, the veiled cells in afferent lymph, induce or enhance responses of lymphocytes to antigens in vitro (1)(2)(3)(4)(5)(6). This class of antigen-presenting cells or accessory cells is characterized by a high level of surface Ia antigen and may be the primary cell type stimulating allogeneic lymphocytes in mixed leukocyte cultures (6)(7)(8)(9)(10)(11).…”

Dendritic cells: Understanding immunogenicity

“…William Bowers [41,42] and Don Mason and Gordon MacPherson [25,43] found active nonadherent accessory cells in thoracic duct lymph of rats, while Brigid Balfour, Hemmo Drexhage and Stella Knight [44][45][46] described similar veiled cells in the afferent lymph of rabbits and guinea pigs. These early observations on distinct cells in different tissues and species were brought together in a review in 1982, where ideas of a DC system were considered [47].…”

Characterization of Human Afferent Lymph Dendritic Cells from Seroma Fluids

“…Thus, they constitute a system that occupies discrete portions of nonlymphoid and lymphoid organs and that is interconnected by defined pathways of movement. Afferent, but not efferent, lymph contains leukocytes termed veiled cells in rabbit (33), pig (34), rat (35), mouse (36), human (6), and sheep (37). Like classical DCs, veiled cells were described as leukocytes displaying a buoyant density, low FcR and phagocytic activity, and high levels of MHC class II and APC activity.…”