Factors influencing immune complex localisation

Circumventricular organs in chronic serum sickness: a model for cerebral lupus

The pathogenesis of the CNS manifestations of systemic lupus erythematosus (SLE) has been the subject of considerable investigation. The focus of many of these studies has concerned immune complex deposition within the choroid plexus (CP). Involvement of the other brain fenestrated vascular beds, the small, paraventricular circumventricular organs, has not been ascertained. For this purpose, chronic serum sickness, a good immunopathological experimental model of naturally occurring systemic immunological disorders such as SLE, was induced in Wistar rats by prolonged immunization with bovine serum albumin (BSA). The involvement of circumventricular vascular beds by immune deposits was ascertained immunohistochemically. The choroid plexus was found to be the most intensely involved circumventricular structure. Immune complex deposits were also present, in descending order of frequency, in the area postrema, subfornical organ, and pineal gland.

Soluble immune complexes in lupus mice: clearance from blood and estimation of formation rates

Elevated levels of circulating immune complexes (IC) occur in patients with systemic lupus erythematosus (SLE) and in several strains of mice that spontaneously develop a lupus-like illness. An increase in circulating IC might occur as a result of increased IC formation or decreased IC clearance. Previous work with one murine lupus strain, NZB/W, demonstrated normal clearance of soluble IC. We studied the in vivo behavior of stable model IgG IC in two murine lupus strains. MRL/l and BXSB, and in two normal strains, C3H/HeN and BALB/c. IC were injected intravenously, and blood radioactivity was measured over 3 hr. A clearance curve was derived for each mouse using the Marquardt-Levenberg curve-fitting method. A formula is derived which predicts the formation rate of IC in each animal from the blood level of IC and the clearance curve parameters. All mice exhibited biphasic exponential clearance of IC over 3 hr. Clearance of IC was significantly slower in MRL/l mice than in normal strains (P less than 0.02), and clearance in BXSB mice was significantly faster than in normals (P less than 0.02). However, the derived formula suggests that the observed differences in IC clearance have only a small effect on the blood levels of IC in the mice studied, and therefore suggests that the major factor which accounts for increased blood levels of IC in lupus mice is an increase in the IC formation rate.

Characterization of circulating Yersinia-specific immune complexes in patients with yersiniosis

The size of immune complexes (ICs) containing Yersinia enterocolitica antigens was studied by size exclusion high-pressure liquid chromatography and sucrose density gradient ultracentrifugation in sera of patients with recent yersiniosis. The ICs detected were relatively small, i.e., of equal size to or slightly larger than the corresponding anti-Yersinia antibodies. The size of the ICs was equal in the patients with Yersinia-triggered reactive arthritis and in those recovering without complications. No changes were observed during a follow-up. The equal size of ICs in the patients with and without arthritis also suggests that antigens and antibodies involved are similar in both patient groups. Taken together with our earlier findings indicating occurrence of high concentrations of Yersinia IgM ICs in the arthritic patients, the present results suggest that Yersinia--IgM ICs have a role in the pathogenesis of Yersinia-triggered reactive arthritis.

Methylprednisolone infusion therapy in rheumatoid arthritis patients. The effect on synovial fluid lymphocyte subsets and inflammatory indices

Paired samples of synovial fluid (SF) and blood were obtained prior to and at 4 and 24 hours following high-dose methylprednisolone infusion therapy in a group of patients with refractory rheumatoid arthritis. After therapy there was a significant decrease in numbers of polymorphonuclear leukocytes, lymphocytes, immune complexes, and C-reactive protein in the SF. Measurement of lymphocyte subsets, using monoclonal antibodies, revealed that at 4 hours postinfusion, there was a disproportionate decrease in the percentage of SF lymphocytes expressing class II antigens (HLA-DR or Ia-like). These data suggest that glucocorticoids induce rapid changes in SF indices of disease activity and may directly influence T cell activation within the rheumatoid joint.

Borderline-tissues as sites of antigen deposition and persistence--a unifying concept of rheumatoid inflammation?

In organs of rheumatoid inflammation avascular tissue is nourished by perfusion either directly from the blood stream or by neighbouring blood vessels (borderline-tissue). An open question remains whether this borderline-tissue promotes only the known antigen persistence, or also the first deposition of the pathogenetically important microbial antigen, and subsequently a deposition of immune complexes. The three markers (carbon, latex, and living bacteria) used in this study led to nearly the same pattern of deposition in two groups of organ systems: Organs with clearance function belonging to the mononuclear phagocyte system (MPS); organs with borderline-tissues: joint, kidney, artery, heart valve, and eye. This deposition at the borderline can be observed best in areas of the joint where highly vascularized tissues are adjacent to avascular tissues nourished via perfusion: perichondrium, peritendineum, periosteum, and endo- and perimysium. These localisations of particle deposition correspond exactly with the intraarticular predilection sites of chronic rheumatoid inflammation in man and animals. Our results indicate an easier settlement of corpuscular material in these localisations, which at the same time are unable to eliminate such substances, unlike the organs of the MPS. Our studies seem to support the theory of pathogenetic importance of the borderline-tissues as a localizing factor in the perpetuating rheumatoid inflammation.