CD79a expression and activation on myeloid cells contributes to their pro-tumorigenic effects <i>in vivo</i>.

<p>(A) Immunofluorescence of normal lung and metastasis-bearing lungs in the LLC model. Infiltrating Gr1+CD79a+ myeloid cells are clearly visible at the outer edge of a lung metastasis but are rare or absent from normal lung tissue. The dotted line marks the outer boundary of the metastasis. Scale bar: 40 µm. (B) Quantification of lung infiltrating Gr1+CD79a+ and Gr1+Cd79-11- myeloid cells: Analysis was done for 3 groups: normal lung, uninvolved lung tissue from metastasis bearing lung, and lung metastasis. Each data point represents the mean of 5 fields (500 µm²) for a given sample and results are given as mean +/− SEM. (C) Immature BM cells from C57Bl/6 mice were FACS sorted into two groups of Ly6C⁺CD79a⁺ and Ly6C⁺ CD79a⁻ myeloid cells. The sorted myeloid cells were co-inoculated together with LLC tumor cells subcutaneously in C57Bl/6 mice at a ratio of 25∶1 myeloid: tumor cells. Tumor weight was measured at day 14 post-inoculation. Results are mean +/− SEM (n = 5). (D) Ly6C+ BM-derived myeloid cells from naïve mice were isolated by FACS and cultured with anti CD79a(v-20) or isotype control antibodies for 24 h. Treated myeloid cells were then harvested and injected i.v. together with luciferase-expressing LLC cells (2×10⁶ myeloid cells and 10⁴ LLC tumor cells/mouse) in C57Bl/6 mice. Metastatic burden was quantitated from <i>in vivo</i> luciferase signal at day 15 after implantation. Results are median with interquartile range (n = 10 mice/group).