Ionizing irradiation damage to the lung is associated with an acute inflammatory reaction, followed by a latent period and then late effects including predominantly pulmonary fibrosis. The cells mediating fibrosis have recently been shown to derive from the bone marrow hematopoietic microenvironment. Initiation of late pulmonary irradiation lung damage has been correlated with up-regulation of VCAM-1 and ICAM-1 in pulmonary endothelial cells, followed by infiltration of macrophages and bone marrow-derived fibroblasts forming the fibrotic lesions of organizing alveolitis/fibrosis. To determine whether the absence of expression of VCAM-1, ICAM-1, or other adhesion molecules known to be relevant to inflammatory cell attachment to lung endothelial cells was associated with a decrease in irradiation-induced lung fibrosis, homozygous deletion recombinant knockout mice lacking each of several adhesion molecules were tested compared to littermates for survival and development of organizing alveolitis following 20 Gy irradiation to both lungs. Bone marrow culture longevity has been shown to be a parameter, which correlates with both hematopoietic stem cell reserve and the integrity of fibroblast progenitors of the supportive hematopoietic microenvironment; radiation lung survival data were correlated to longevity of hematopoiesis in long-term bone marrow cultures established from tibia and femur bone marrow of the same mice. Homozygous deletion recombinant negative mice including VCAM-1-/-, ICAM-1-/-, E-Selectin-/-, or L-Selectin-/- were irradiated to 20 Gy to both lungs and followed for survival and percent organizing alveolitis at time of death compared to each normal littermate. A significant increase in survival (median 190 days) was detected with L-Selectin-/- compared to littermate control mice (median 140 days) or other groups. Long-term bone marrow cultures from L-Selectin-/- mice showed no detectable difference in marrow fibroblasts or hematopoietic cell biology compared to normal littermates; however, E-Selectin-/- mouse long-term bone marrow cultures showed an increase in total cumulative cell production (1.7 x 10(8) cells per flask) compared to bone marrow cultures from normal littermates (1.8 x 10(6) cells per flask) or other groups. As additional controls, transgenic Sod2 mouse long-term bone marrow cultures and those from HPV16, E6 and E7 cytokeratin 14 transgenic mice were also tested. No detectable difference in hematopoiesis was noted in these cultures compared to littermates. The results suggest a complex pattern of involvement of endothelial specific adhesion molecules and marrow fibroblasts in the cell biologic events associated with late irradiation pulmonary fibrosis.