Dendritic cells as accessory cells in antigen-specific murine T lymphocyte proliferation in vitro

Accessory cell requirements in mitogen-induced rabbit T lymphocyte proliferation in an improved tissue culture system

The impact of an improved culture medium (IMDM+), consisting of Iscove's modified Dulbecco's medium supplemented with albumin, transferrin, insulin, zinc, 2-mercapthoethanel, and 0.1% fetal bovine serum was investigated in phytohemagglutinin (PHA)-induced rabbit T cell proliferation. At the number of 2 X 10(5) cells/well purified T lymphocytes cultured in IMDM+ responded 3 to 10 times better than lymphocytes cultured in serum-supplemented RPMI 1640 medium. In these conditions, PHA-induced proliferation seemed not to require the presence of accessory cells. However, at lower cell numbers, T cell proliferation was more efficient when calculated on a per cell basis. At these low cell numbers, optimal proliferation required accessory cells like macrophages or dendritic cells. The apparent absence of this requirement for accessory cells at high T cell concentrations may be explained by the contribution of contaminating macrophages and dendritic cells in the purified T cell fractions.

Antigen-presenting cell function of dendritic cells and macrophages in proliferative T cell responses to soluble and particulate antigens

The capacity of dendritic cells (DC) and macrophages (M phi) to present soluble and particulate antigen was tested in an ovalbumin (OVA)-specific T cell proliferation assay. In a comparative investigation we found that both DC and M phi were able to present soluble OVA, but that only M phi could present insolubilized OVA to T cells. DC were found to be able to present OVA in collaboration with M phi. The failure of DC to present insolubilized OVA is probably caused by their inability to endocytose these antigens. DC appeared not to endocytose substantial amounts of soluble OVA either. In contrast to M phi, antigen presentation by DC is not blocked by lysosomotropic drugs. Taken together, these observations suggest that DC can present soluble protein antigens without intracellular degradation.