Rat CD4+CD8+ Macrophages Kill Tumor Cells through an NKG2D- and Granzyme/Perforin-Dependent Mechanism

Abstract

We previously identified a subpopulation of monocyte/macrophage lineage cells expressing both CD4 and CD8. This subpopulation was expanded in rat peripheral blood and spleen after immunization with adjuvants containing killed tuberculosis germs. CD4+CD8+ monocytes/macrophages obtained from preimmunized rats exhibited a Th1-type cytokine/chemokine profile, expressed high levels of Fas ligand, perforin, granzyme B, and NKR-P2 (rat ortholog of human NKG2D), and killed certain tumor cells. In the present study, we confirmed that CD4+CD8+ monocytes/macrophages are distinct from splenic dendritic cells (DCs) or IFN-producing killer DCs. In vitro cytotoxic assays revealed that CD4+CD8+ macrophages killed tumor cells in a cell-cell contact-dependent manner and that expression of the retinoic acid early transcript 1 (a ligand for NKG2D) made tumor cells susceptible to killing by CD4+CD8+ macrophages. Furthermore, inhibitors of granzyme and perforin significantly decreased cytotoxic activities of CD4+CD8+ macrophages. Consistent with these in vitro findings, preimmunization with adjuvants containing killed tuberculosis germs elevated the expression of granzyme B in tumor-infiltrating CD4+CD8+ macrophages and significantly inhibited the growth of inoculated tumor cells. Our current work demonstrates that CD4+CD8+ macrophages are a unique subpopulation of monocyte/macrophage lineage cells that kill tumor cells in an NKG2D- and granzyme/perforin-dependent mechanism.

Isolation of Epithelial, Endothelial, and Immune Cells from Lungs of Transgenic Mice with Oncogene-Induced Lung Adenocarcinomas

“…We found that approximately 91% of the CD45 pos cells were double positive for CD45 and F4/80 (a macrophage marker; Figure 2D, II), and approximately 16.1% of the population was double positive for CD45 and CD3 (T cell marker; Figure 2D, III). Of note, cells that express both macrophage and lymphoid markers have been described, which explains why we observed a small fraction of cells that are both F4/80 pos and CD3 pos (36).…”

Three major uncertainties in the antibody therapy of cancer

“…Whether the classical method by which macrophages enact ADCC (phagocytosis by the zipper mechanism 46,47 ) is available on the scale required remains to be determined. An observation of NK-type extracellular killing (utilizing granzymes and perforin) performed by a subset of rat macrophages has been recorded 48 but no similar reports have been found. Hubert et al 22 have described synapses formed in mice, during tumor rejection, between antibody-coated tumor cells and macrophages or neutrophils.…”

Chlamydia trachomatis serovar L2 infection model using human lymphoid Jurkat cells

“…Although further study is necessary to clarify how such molecular alteration was directly involved in a failure of C. trachomatis replication, such mutant cells are potentially useful for elucidating the interaction of pathogenic chlamydiae with lymphocytes. In addition, recent works using animals revealed that granzyme was expressed and produced not only in T cells or NK cells, but also in macrophages, although a counterpart in humans is yet to be discovered [41,42].…”