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PubMed1957

The properdin system and immunity. VII. Alterations in properdin levels and resistance to infection in mice following the administration of tissue polysaccharides.

High molecular weight polysaccharide complexes derived from normal and neoplastic mammalian tissues were found to combine with properdin and to inactivate C'3 in vitro. These polysaccharide preparations were also found to alter properdin levels and non-specific resistance to Gram-negative infection in mice. In these manifestations, the tissue polysaccharides bore a marked resemblance to bacterial lipopolysaccharides. Some implications of the interactions of tissue polysaccharides and properdin in certain disease states are considered.

Animals↗
PubMed1978

Binding of activated properdin to untreated erythrocytes: a new function of activated properdin.

Activated human properdin was found to be capable of binding to rabbit and sheep erythrocytes to form new intermediate cells of the alternative pathway of the complement system. The intermediate cells, termed EP, can react with B, D and C3 to form other intermediate cells, tentatively termed EPB(D)C3, which can be lysed by the subsequent action of six late-acting complement components, C3 to C9. The possibility of participation of C3, B, D or immunoglobulin in the formation of EP cells was neglected by the experiments in which the inhibition of the reactivities of P or EP by antisera to P, C3, B, D or immunoglobulins were investigated. The reduction in reactivities of P to E, or of EP to B, D and C3 was observed only when pretreated with antiserum to P. Furthermore, EP cells were agglutinated only by anti-P, not by antisera to C3 or IgG. The other possibility of participation of the classical complement components such as antibody, C1, C4 and C2 in the formation of EPB(D)C3 was excluded by the non-reactivities of EP with C4 and C2 and of EAC1 with B, D and C3. Thus, activated properdin is likely to function not only as modulator of preformed enzyme such as C3bBb but also as one of early-acting components of the alternative pathway.

Agglutination↗
PubMed1975

Properdin- and nephritic factor-dependent C3 convertases: requirement of native C3 for enzyme formation and the function of bound C3b as properdin receptor.

Two complex enzymes were assembled that both converted C3 to C3b, one consisting of activated properdin (P), native C3, proactivator (PA) and proactivator convertase (PAase), and the other of nephritic factor (NF) and the same three cofactors. By maintaining a critical concentration of PAase, the P-C3 convertase and the NF-C3 convertase were shown to function efficiently without formation of the C3b-feedback enzyme. The former two enzymes are distinct from the C3b-dependent C3 convertase in that they utilize native C3 instead of C3b and PA in an apparently uncleaved form. The P- and NF-C3 convertase express maximal activity within approximately 10 min at 37 degrees C and decay with a half-life of 35 min at 37 degrees C, which is in contradistinction to the reported lability of the C3b-feedback enzyme. P- and NF-C3 convertases are inhibited by their product C3b, which may constitute a heretofore unknown control of the alternative pathway. A direct physical interaction of P with native C3 and C3b was demonstrated by agglutination of C3b-bearing erythrocytes and by agglutination inhibition. Bound C3b thus constitutes the only known receptor of P and may fulfill an important localizing function for P and the P-C3 convertase in vivo. Although P and NF form functionally similar enzymes, they act independently of each other and are apparently immunochemically unrelated proteins.

Absorption↗
PubMed1988

A second variant of properdin deficiency: the detection of properdin at low concentrations in affected males.

A selective deficiency of properdin (P) was identified in a 58-year-old male and in his 29-year-old nephew, both of whom were clinically healthy. As determined by different immunochemical methods P at low concentrations (about 2 mg/l) was detectable in serum and plasma. Three female relatives, including the mother and daughter of one of the P-deficient males showed moderately low P concentrations. The findings clearly suggested that the deficiency was inherited as an X-linked trait. Three males belonging to another family with P deficiency also showed detectable P concentrations. By contrast, no P (less than 0.1 mg/l) was found in 8 males belonging to three other families. We suggest that there are two variants of X-linked P deficiency: P deficiency type 1, characterized by extremely low P concentrations (less than 0.1 mg/l); and P deficiency type 2 recognizable by P concentrations of about 2 mg/l. The P detected in P deficiency type 2 had subunits of normal molecular weight (52 kilodaltons), but eluted in a lower molecular weight range than did the P of normal serum, either on gel filtration (Ultrogel AcA 22) or on size exclusion chromatography (TSK-4000). The evidence suggested that the P concentration may be one determinant of P oligomer formation. P-deficient serum type 2 did not support fluid phase C3 cleavage in the presence of such alternative pathway activators as inulin and zymosan, nor did it support efficient lysis of guinea pig erythrocytes in agarose gel. By contrast, rabbit erythrocytes were efficiently lyzed, but at a slow rate. P-deficient serum type 1 did not support lysis of rabbit erythrocytes in the assay system used. The reaction was clearly promoted by very low concentrations of purified P. Partially purified P from a male with P deficiency type 2 was shown to be hemolytically active. Further evidence of P function in P deficiency type 2 was obtained by using IgG-presensitized serogroup W-135 meningococci in an alternative pathway-mediated serum bactericidal assay.

Adult↗
PubMed1976

[Contributions to the study of properdin. 4. Report: in vitro model study on the effect of cattle properdin on Escherichia coli].

Light and electron microscopy were used in model experiments to study a high-titre "properdine-system" culture and its action in terms of altering E. coli bacteria. The reaction was altogether strongly predominated by the three following phases of lysis. 1. Onset of massive agglutination after few minutes; 2. Decomposition of bacterial structure by lysis after ten to twelve hours; 3. Terminal phase of lysis after two to three days (amorphous detritus).

Agglutination↗