[Suppression of macrophage subpopulations in post-traumatic osteomyelitis]

Local and systemic inflammatory mediator release in patients with acute and chronic posttraumatic osteomyelitis

The local and systemic release of thromboxane A2, prostaglandin I2, leukotriene B4 (LTB4), tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and interleukin-8 (IL-8) were studied before and after operation in 29 patients with acute and 22 with chronic posttraumatic osteomyelitis. Twenty patients without osteomyelitis, who underwent operations for fractures of the lower extremities, served as controls. Blood and tissue samples from the osteomyelitic and control groups were collected under defined conditions and mediators were determined by radioimmunoassay (thromboxane B2, 6-keto-prostaglandin F1 alpha, LTB4) or by enzyme-linked immunosorbent assay (TNF-alpha, IL-1 beta, and IL-8). In addition, common parameters (leukocyte count, C-reactive protein, temperature) were measured. The best correlation with acute disease activity was given by TNF-alpha, IL-6, IL-8, and LTB4. Plasma levels of these mediators in acute osteomyelitis were significantly increased compared to chronic osteomyelitis and to controls, respectively. Tissue samples from osteomyelitic focus showed significantly increased levels for IL-8, IL-6, TNF-alpha, IL-1 beta, and LTB4 in acute osteomyelitis, whereas the values for TxB2 and 6-keto-prostaglandin F1 alpha were only slightly increased compared to the chronic osteomyelitis group. This study describes the local and systemic liberation of various mediators in acute and chronic posttraumatic osteomyelitis in detail for the first time and provides data for pre- and postoperative monitoring of disease activity and demonstrates new pathogenetic and therapeutic aspects of bone modulation in osteomyelitis.

Macrophage reactions in septic arthritis

With the aid of monoclonal antibodies, macrophages can be split into functionally distinct subpopulations on the basis of their phenotype. Absence of macrophage subtypes has been noted in chronic inflammatory processes, e.g. posttraumatic osteomyelitis, rheumatoid arthritis and sarcoidosis. In the inflammatory focus of acute septic arthritis (n = 13 patients) however, macrophages constitute the majority of immunocompetent cells. The inflammatory macrophage subtype 27E10 was clearly present in increased numbers in 11 of 13 biopsies from the inflammatory foci, showing the effector task of this subtype in synovial resistance. The anti-inflammatory macrophage subset RM3/1 was present in increased numbers in biopsies of infected tissue and the surrounding soft tissue. The occurrence of 25F9-positive macrophages, typical of the late phase of inflammation, varied widely in the biopsies.

Pattern of macrophage subpopulations in post-traumatic bone infections after combined operative/antibiotic treatment

Macrophage subpopulations were detected immunohistochemically with the aid of monoclonal antibodies in tissue sections of 15 patients with posttraumatic osteomyelitis at the beginning of therapy and after combined operative/antibiotic treatment. Macrophages represent the majority of the immunocompetent cells in osteomyelitis tissue. Before the start of therapy, the acute inflammatory macrophage subtype 27E10 was absent or rarely found in 8/13 evaluable biopsies from the osteomyelitis focus, and a further decrease in the expression of these macrophage antigens was observed after treatment. The RM3/1-positive macrophage associated with the down-regulation of inflammation was detectable to a low extent in 4/13 evaluable biopsies from the osteomyelitis focus before the start of therapy. After treatment of the infection, an increase in this subtype was found in the cellular inflammatory infiltrates in the tissue samples examined. In 8/15 biopsies a marked expression of the RM3/1 antigen was observed. At the start of treatment, the macrophage 25F9, which dominates in the late phase of inflammation, was missing in 3/13 tissue samples. After combined operative/antibiotic treatment the 25F9-positive macrophage was found in all patients, having increased in 7/14 biopsies studied. These data suggest that treatment of posttraumatic osteomyelitis leads to a local macrophage subtype distribution in the osteomyelitis focus resembling the pattern of a late inflammatory reaction.