Activation of the classical and alternative pathways of complement fixation by immune complexes containing normal and tryptophan-modified immunoglobulin G

Koshland's reagent (2-hydroxy-5-nitrobenzyl bromide (NBB)) has been shown to modify tryptophanyl residues in anti-ovalbumin IgG. As little as 2 moles NBB/mole IgG antibody are sufficient to block the classical pathway of complement activation when the antibody is complexed to antigen (ovalbumin). In contrast, immune complexes containing antibody with the same degree of tryptophanyl substitution will activate the alternative pathway of complement fixation. Immune complexes containing F(ab')2 fragments derived from anti-ovalbumin IgG do not activate the classical pathway. When measuring the percentage activation of C3 using the method of Laurell, NBB does not affect the alternative pathway of the complement system up to a molar ratio of 2 NBB/F(ab')2. The above findings, provide a means to evaluate the relative contribution of complement activation by the different pathways.     

Special indications, contraindications, particular methods of treatment in correction with intraocular lenses (author's transl)]

For the past 5 3/4 years intraocular lens implantion belongs to the routine operations performed in the Lucerne Eye Clinic. Whereas unilateral cataracts are the main and frequent indication for intraocular lens implants, there are certain cases of uni- and bilateral cataracts also, where the implantation of intraocular lens, due to its advantages, is specially indicated. Such cases are presented briefly in this paper. Good results are achieved through strictly observing the methods of treatment before and after the implantation of the lens.     

Fibronectin binds to the C1q component of complement.

Fibronectin immobilized to plastic tubes binds soluble C1q with a Kd of 82 +/- 2.6 nM. The binding of fibronectin to C1q is relatively insensitive to pH but is sensitive to ionic conditions. C1q covalently bound to Sepharose selectively binds cellular fibronectin produced by a hamster fibroblast cell line. The globular head regions of C1q have no effect on the binding of C1q to fibronectin but the collagenous tails of C1q interfere competitively with a Ki of 59 nM. We conclude that fibronectin binds C1q via its collagen-like tail region and thus the process resembles the binding of fibronectin to gelatin. This is further emphasized by our observation that gelatin binds to fibronectin immobilized on plastic tubes with a Kd of 131 nM. Because fibronectin stimulates endocytosis in several systems and promotes the clearance of particulate material from the circulation, these results suggest the possibility that fibronectin could function in the clearance of C1q-coated material such as immune complexes or cellular debris.