The occurrence of accessory immunologic cells in bone induction.
The differentiating tissues in fracture healing and in demineralized bone-powder-induced (DBP) bone formation were investigated with monoclonal antibodies with respect to the occurrence of Ia-positive cells, macrophages, and lymphocytes with interleukin-2 receptors (IL-2). Ia refers to molecules on the cell surface belonging to Class II of the major histocompatibility complex and is specific for the species and the individual. In both types of granulation tissues (fracture healing and following DBP implantation), the mesenchymal cells from the surrounding musculature were accompanied by large numbers of Ia-positive cells and common macrophages. The occurrence of IL-2 receptors was sparse in fracture healing but rich in DBP induction, probably because of its immunogenic properties, though weak. On Day 7, almost all existing cells in DBP induction were Ia-positive, signifying an immunologic effector phase apparently directed to the remaining still-passive bone powder in the periphery, while the central part of the inserted bone powder was producing cartilaginous cells and matrix. The presence of accessory immunologic cells in fracture healing is perhaps due to a surveillance function (a standard response on injury), but the cell differentiation might also be dependent on the active mediators emitted from Ia-positive cells and macrophages. This investigation strengthens the concept that induced bone development occurs in experimental fracture healing.
Henricson
A
A
Department of Orthopedics, Malmö General Hospital, Lund University, Sweden.
Hulth
A
A
Johnell
O
O
D000818:Animals; D000911:Antibodies, Monoclonal; D000938:Antigen-Presenting Cells / Q000276:immunology*; D005260:Female; D050723:Fractures, Bone / Q000276:immunology*; D006097:Granulation Tissue / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D007150:Immunohistochemistry; D008214:Lymphocytes / Q000276:immunology; D008264:Macrophages / Q000276:immunology; D008297:Male; D008648:Mesoderm / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D015375:Receptors, Interleukin-2 / Q000032:analysis; D014945:Wound Healing / Q000276:immunology
D000911:Antibodies, Monoclonal; D000949:Histocompatibility Antigens Class II; D015375:Receptors, Interleukin-2