Immunogenicity of Ly5 (CD45)‐Antigens Hampers Long‐Term Engraftment Following Minimal Conditioning in a Murine Bone Marrow Transplantation Model

Abstract

Various techniques are available for distinguishing donor from host cells evaluating the efficacy of conditioning regimen for experimental bone marrow transplantation (BMT). Techniques include the use of extracellular immunological markers, such as Ly5 (CD45), and intracellular biochemical markers, such as glucose-phosphate-isomerase (Gpi). Because Ly5 is an extracellular protein, the disparity between donor (Ly5.1) and host (Ly5.2) antigens may induce a weak immune response whereas with Gpi, no immune response is expected. This difference may be of particular concern in experimental transplantation approaches that use minimal conditioning such as low-dose total body irradiation (TBI). Such mild conditioning may not induce the immunosuppression required to overcome host rejection of Ly5 disparate cells.To ). However, when higher TBI or BMC doses were used, similar engraftment levels were found, suggesting sufficient immune suppression to allow equal engraftment of both sources of BM.These data suggest that even a minor phenotypic disparity between donor and host, such as Ly5, may necessitate high-dose TBI to prevent rejection. The combination of low-dose TBI or other nonmyeloablative conditioning strategies with small numbers of BMC may lead to reduced engraftment when extracellular immunological markers such as Ly5 are used for transplantation studies. Therefore, small immunological differences must be considered when using the Ly5 marker for engraftment.

IFN-γ Production by Intrinsic Renal Cells and Bone Marrow-Derived Cells Is Required for Full Expression of Crescentic Glomerulonephritis in Mice

“…The efficiency of BM replacement following transplantation was assessed using congenic CD45 mouse strains (Ly5.1 and Ly5.2). Eight weeks after irradiation and transplantation 92 Ϯ 1% of circulating leukocytes, 98 Ϯ 1% of BM leukocytes, and 90 Ϯ 2% of splenic leukocytes expressed the phenotypic marker of the transplanted BM (n ϭ 6), similar to previous reports (30,31). Resident CD45-positive cells of either strain were rarely detectable by immunofluorescence in kidneys of normal mice or mice that had undergone BM transplantation before induction of GN.…”

Local irradiation enhances congenic donor pluripotent hematopoietic stem cell engraftment similarly in irradiated and nonirradiated sites

“…Since our studies involved much higher doses than those reported, 24 and studies in the Ly5 congenic combination in the same direction used here showed no evidence of immune recognition, 15 we do not believe that immune responses are likely to contribute to the phenomena reported here.…”

“…Although CD45.2 mice have been shown to be capable of mounting an immune response to congenic CD45.1 donors (transplantation in the opposite direction to the one used here), 24 the immune resistance in this combination was readily overcome by increasing the donor marrow dose. Since our studies involved much higher doses than those reported, 24 and studies in the Ly5 congenic combination in the same direction used here showed no evidence of immune recognition, 15 we do not believe that immune responses are likely to contribute to the phenomena reported here.…”

Effects of fluorescent and nonfluorescent tracing methods on lymphocyte migration in vivo

“…Therefore, it well may be that in these experiments depletion from the circulation rather than disturbed migration was the cause of these effects because the unequal distribution was found not only found in lymph nodes but also in blood and spleen. Although functional differences between congenic mouse strains would not be expected due to their genetic resemblance, it has been shown that the small differences between these Ly5 allotypes can cause differences in in vitro immune responses (29) and can even decrease long-term donor engraftment upon congenic bone marrow transplantation (30). These findings indicate that even B6-Ly5.1 and B6-Ly5.2 mice are functionally more distinct than would be expected from the small genetic difference in the Ly5 gene only.…”