title: Evaluation of immune cell markers in tumor tissue treated with radioimmunotherapy in an immunocompetent rat colon carcinoma model.
abstract: BACKGROUND
  Immune cells within the tumor can act either to promote growth or rejection of tumor cells. The aim of the present study was to evaluate immune cell markers (number and localization) within the tumor before and during rejection due to radioimmunotherapy, to determine whether there is a change in markers related to rejection and/or tolerance of the tumor cells.
  
  
  METHODS
  Thirty immunocompetent rats were inoculated with syngeneic rat colon carcinoma cells and 13-14 days later 21 of these rats were treated with 400 MBq/kg of (177)Lu-DOTA-BR96 monoclonal antibodies. The treated animals were sacrificed and dissected 1, 2, 3, 4, 6, and 8 days post-injection in groups of three animals per day (6 animals on day 8); while the nine untreated animals were sacrificed and dissected on day 0. Paraffin sections were used for immunohistochemical staining of CD2, CD3, CD8α, CD68, and CD163 antigens. Positive cells were counted within: vital tumor cell areas, necrotic areas, granulation tissue surrounding and between the tumor cell areas. The change in the number of positive cells over time in tumors treated with radioimmunotherapy in the same location was evaluated with linear regression models. The number of positive cells in various locations and the number of various antigen-positive cells within the same location were also evaluated over time using box plots.
  
  
  RESULTS
  There were a higher number of cells expressing immune cell markers in granulation tissue compared with vital tumor cell areas. Cells expressing markers decreased during radioimmunotherapy, and T-cell markers decreased more than macrophage markers in tumors treated with radioimmunotherapy. The expression of CD8α was higher than that of the other T-cell markers evaluated (CD3 and CD2), which could be explained by the additional expression of CD8α by natural killer (NK) cells and a subset of dendritic cells (DCs). The expression of CD68 (all macrophages, DCs, and neutrophils) tended to be higher than that of CD163 (pro-tumor macrophages).
  
  
  CONCLUSIONS
  In this model, we demonstrated a higher number of positive cells for immune cell markers related to augmenting the immune rejection than immune tolerance of tumor cells in tumors and a decrease in markers during radioimmunotherapy.
authors.affiliation: Department of Clinical Sciences Lund, Division of Oncology and Pathology, Lund University, Barngatan 2B, SE-221 85, Lund, Sweden. Erika.Elgstrom@med.lu.se.
authors.forename: Erika
authors.initials: E
authors.lastname: Elgström
authors.affiliation: Department of Clinical Sciences Lund, Division of Oncology and Pathology, Lund University, Barngatan 2B, SE-221 85, Lund, Sweden. Sophie.Eriksson@med.lu.se.
authors.forename: Sophie E
authors.initials: SE
authors.lastname: Eriksson
authors.affiliation: Department of Laboratory Medicine, Clinical Pathology, Skane University Hospital, Lund, Sweden. Otto.Ljungberg@skane.se.
authors.forename: Otto
authors.initials: O
authors.lastname: Ljungberg
authors.affiliation: Department of Clinical Sciences Lund, Division of Oncology and Pathology, Lund University, Barngatan 2B, SE-221 85, Lund, Sweden. Par-Ola.Bendahl@med.lu.se.
authors.forename: Pär-Ola
authors.initials: PO
authors.lastname: Bendahl
authors.affiliation: Department of Medical Radiation Physics, Lund University, Lund, Sweden. Tomas.G.Olsson@skane.se.
authors.forename: Tomas G
authors.initials: TG
authors.lastname: Ohlsson
authors.affiliation: Department of Clinical Sciences Lund, Division of Oncology and Pathology, Lund University, Barngatan 2B, SE-221 85, Lund, Sweden. Rune.Nilsson@med.lu.se.
authors.forename: Rune
authors.initials: R
authors.lastname: Nilsson
authors.affiliation: Department of Clinical Sciences Lund, Division of Oncology and Pathology, Lund University, Barngatan 2B, SE-221 85, Lund, Sweden. Jan.Tennvall@med.lu.se.|Department of Oncology, Skane University Hospital, Lund, Sweden. Jan.Tennvall@med.lu.se.
authors.forename: Jan
authors.initials: J
authors.lastname: Tennvall
keywords: CD163; CD2; CD3; CD68; CD8; Immune cells; Immune rejection; Immunocompetent; Radioimmunotherapy; Tumor microenvironment