Irradiation induces increase of adhesion molecules and accumulation of beta2-integrin-expressing cells in humans.

PURPOSE: The purpose of our investigation was to describe the dose- and time-dependent histomorphologic alterations of the irradiated tissue, the composition of the infiltrate, and the expression patterns of various adhesion molecules. METHODS AND MATERIALS: We analyzed immunohistochemically alterations in oral mucosa in 13 head and neck cancer patients before radiotherapy and with 30 Gy and 60 Gy. All had oral mucosa irradiation, with a final dose of 60 Gy using conventional fractionation. Snap-frozen specimens were stained using the indirect immunperoxidase technique. Histomorphology was studied in paraffin-embedded sections. In addition, we determined the clinical degree of oral mucositis. RESULTS: Histomorphologic evaluation showed no vascular damage. Irradiation caused a steep increase of beta2-integrin-bearing cells (p < 0.01), whereas the percentage of beta1-integrin-positive cells remained at low levels. Additionally we found an increase in the expression of endothelial intercellular adhesion molecule-1 (ICAM-1) (p < 0.01) and E-selectin (p < 0.05), while endothelial vascular cell adhesion molecule-1 (VCAM-1) expression remained at very low levels. CONCLUSION: Our findings indicate that in radiation-induced oral mucositis there is no marked vascular damage until the end of radiotherapy. For recruitment of leukocytes, beta2 is more involved than beta1. Pharmaceuticals that block leukocyte adhesion to E-selectin or ICAM-1 may prevent radiation-mediated inflammation in oral mucosa.

Murine hematopoietic progenitor cells with colony-forming or radioprotective capacity lack expression of the beta 2-integrin LFA-1.

Recently, we have demonstrated that antibodies that block the function of the beta2-integrin leukocyte function-associated antigen-1 (LFA-1) completely abrogate the rapid mobilization of hematopoietic progenitor cells (HPC) with colony-forming and radioprotective capacity induced by interleukin-8 (IL-8) in mice. These findings suggested a direct inhibitory effect of these antibodies on LFA-1-mediated transmigration of stem cells through the bone marrow endothelium. Therefore, we studied the expression and functional role of LFA-1 on murine HPC in vitro and in vivo. In steady state bone marrow +/- 50% of the mononuclear cells (MNC) were LFA-1(neg). Cultures of sorted cells, supplemented with granulocyte colony-stimulating factor (G-CSF)/granulocyte-macrophage colony-stimulating factor (GM-CSF)/IL-1/IL-3/IL-6/stem cell factor (SCF) and erythropoietin (EPO) indicated that the LFA-1(neg) fraction contained the majority of the colony-forming cells (CFCs) (LFA-1(neg) 183 +/- 62/7,500 cells v LFA-1(pos) 29 +/- 17/7,500 cells, P <.001). We found that the radioprotective capacity resided almost exclusively in the LFA-1(neg) cell fraction, the radioprotection rate after transplantation of 10(3), 3 x 10(3), 10(4), and 3 x 10(4) cells being 63%, 90%, 100%, and 100% respectively. Hardly any radioprotection was obtained from LFA-1(pos) cells. Similarly, in cytokine (IL-8 and G-CSF)-mobilized blood, the LFA-1(neg) fraction, which comprised 5% to 10% of the MNC, contained the majority of the colony-forming cells, as well as almost all cells with radioprotective capacity. Subsequently, primitive bone marrow-derived HPC, represented by Wheat-germ-agglutinin (WGA)+/Lineage (Lin)-/Rhodamine (Rho)- sorted cells, were examined. More than 95% of the Rho- cells were LFA-1(neg). Cultures of sorted cells showed that the LFA-1(neg) fraction contained all CFU. Transplantation of 150 Rho- LFA-1(neg) or up to 600 Rho-LFA-1(pos) cells protected 100% and 0% of lethally irradiated recipient mice, respectively. These results show that primitive murine HPC in steady-state bone marrow and of cytokine-mobilized blood do not express LFA-1.