The use of phagocytic peritoneal exudate cells as targets for the estimation of cytotoxic T cell activity

Both Dendritic Cells and Macrophages Can Stimulate Naive CD8 T Cells In Vivo to Proliferate, Develop Effector Function, and Differentiate into Memory Cells

The generation of T cell immunity requires the acquisition and presentation of Ag on bone marrow-derived APCs. Dendritic cells (DC) are believed to be the most potent bone marrow-derived APCs, and the only ones that can stimulate naive T cells to productively respond to Ags. Because macrophages (Mphi) are bone marrow-derived APCs that are also found in tissues and lymphoid organs, can acquire and present Ag, and can express costimulatory molecules, we have investigated their potential to stimulate primary T cell responses in vivo. We find that both injected Mphi and DCs can migrate from peripheral tissues or blood into lymphoid organs. Moreover, injection of peptide-pulsed Mphi or DCs into mice stimulates CD8 T cells to proliferate, express effector functions including cytokine production and cytolysis, and differentiate into long-lived memory cells. Mphi and DCs stimulate T cells directly without requiring cross-presentation of Ag on host APCs. Therefore, more than one type of bone marrow-derived APC has the potential to prime T cell immunity. In contrast, another bone marrow-derived cell, the T lymphocyte, although capable of presenting Ag and homing to the T cell areas of lymphoid organs, is unable to stimulate primary responses. Because Mphi can be very abundant cells, especially at sites of infection and inflammation, they have the potential to play an important role in immune surveillance and the initiation of T cell immunity.

Vaccinia virus proteins on the plasma membrane of infected cells. III. Infection of peritoneal macrophages

Primary macrophage cultures were prepared from the peritoneal exudate cell population harvested from mice challenged intraperitoneally with saline, thioglycollate, or vaccinia virus. Vaccinia virus was adsorbed and penetrated into primary macrophages and L-cells with similar kinetics. As evidenced by the expression of some "early" virus-specified proteins, partial uncoating and activation of the virion-associated DNA-dependent RNA polymerase occurred in the infected macrophages. Subsequently, the viral replication cycle in macrophages was aborted; with time after infection, viral DNA and virion proteins initially associated with infected cells could be detected in an acid-soluble form in the medium harvested from infected macrophage cultures. The results suggest that at the time that the final stages of virus uncoating should have occurred, intracellular subviral particles were, instead, degraded in the infected, primary macrophages. Viral DNA synthesis could not be measured in vaccinia virus-infected macrophages, no "late" virus functions were expressed, and progeny virions were not assembled. As measured by the binding of antiviral-antibody-125I-protein A complexes to the surface of vaccinia virus-infected cells, the expression of virus-specified antigens on the surfaces of infected macrophages was significantly reduced and never exceeded that measured at 2 hr after infection on the surfaces of infected L-cells. The expression of virus-specified polypeptides with mol mass of 48-50, 45-46, 36-37, and 25 kDa on the plasma membranes of vaccinia virus-infected, thioglycollate-elicited macrophages, rendered the infected macrophages susceptible to lysis by vaccinia virus-specific cytotoxic T-cells.