Cr1, CD35 IN synovial fluid from patients with inflammatory joint diseases

Abstract

Objective. To investigate synovial fluid (SF) for the presence of CR1 and to study its relationship to SF leukocytes and to serum levels of soluble CR1 (sCR1) in patients with rheumatic diseases.Methods. Synovial fluids were collected from 35 patients with rheumatoid arthritis (RA) and 26 patients with other inflammatory joint diseases. Total CR1 in the SF and serum were measured with a sandwich enzymelinked immunosorbent assay (ELISA) that recognized both soluble and transmembrane forms of CR1. The characteristics of CR1 in SF were analyzed by ultracentrifugation and by a second ELISA specific for transmembrane CR1.Results. CR1 was found in all SF samples tested (range 5-281 ng/ml). SF CR1 was higher in patients with RA (mean f SD 81 -C 66 ng/ml) than in those with other inflammatory joint diseases (31.8 & 23.8 ng/ml) (P < 0.001). Serum sCRl was not significantly increased in the patients compared with the normal subjects. There was no correlation between serum sCRl and SF CR1. In 44% of the patients, the SF CR1 level was higher than the serum sCRl level. A fraction (3040%) of SF CR1 was pelleted by ultracentrifugation and, unlike serum sCR1, it reacted in an ELISA specific for transmembrane CR1. Thus, SF contained 2 forms of CRl: a membrane-associated and a soluble form, which was confirmed by sucrose density-gradient ultracentrifugation. SF CR1 levels correlated directly with the number of SF total leukocytes and polymorphonuclear

Soluble complement receptor 1 is increased in patients with leukemia and after administration of granulocyte colony-stimulating factor

“…We have recently shown that leukocytes release two different forms of CR1 [18]. The first form corresponds to the shedding of the extracellular domain of the transmembrane molecule (sCR1), whereas the second is still bound to membranes.…”

“…The limit of sensitivity was 0.1 ng/mL. The solubility of CR1 in plasma was assessed before and after ultracentrifugation at 200,000 g at 4°C for 1 h. This centrifugation has been shown to pellet vesicle-bound CR1 of erythrocyte-derived and podocyte-derived vesicles [16,17] as well as leukocyte membranes [18].…”

“…None of the results obtained provided any significant difference. Ultracentrifugation is known to pellet CR1 bound to vesicles derived from erythrocytes and podocytes, as well as CR1 bound to polymorphonuclear leukocyte membranes [16][17][18]. By contrast, sCR1 is not pelleted by ultracentrifugation [8,9].…”

“…The CR1 attached to microvesicles released from cells corresponds to the whole transmembrane CR1 [18]. The ELISA specific for transmembrane CR1 (mCR1) [7] does not recognize sCR1 (see Patients and Methods).…”

Soluble complement receptor type 1 (CD35) in bronchoalveolar lavage of inflammatory lung diseases

“…This important physiological complement inhibitor found in the respiratory tract in soluble form, contrarily to the epithelium-bound complement regulatory proteins membrane cofactor protein, decay-accelerating factor and CD59 [9], may be important to prevent lung injury in several acute and chronic inflammations. The observation that soluble complement receptor type 1 could be measured in bronchoalveolar lavage with a monoclonal antibody known to recognise the C3b/ C4b binding sites suggests that the molecule is functional [46,47]. Whether this complement receptor type 1 release is sufficient to inhibit complement activation in vivo remains to be determined.…”