Purification of the first component of human complement and its subunit C1 esterase

Transition-state affinity chromatography of trypsin-like proteinases with dipeptidyl argininal ligands

Dipeptidyl argininal (arginine aldehyde) affinity resins of general formula R-(X-Y-argininal) (where R = resin matrix and X, Y = amino acids of varied structure) are synthesized in a solid-phase procedure in which the dipeptide (-X-Y-) is first attached to the resin, followed by the joining of the Y amino acid to argininal semicarbazone, and decomposition of the semicarbazone in a methanol/acetic acid/formaldehyde reagent. An R-(Gly-Gly-argininal) resin binds urokinase tightly, but does not bind thrombin. However, thrombin binds strongly to R-(Phe-Pro-argininal), whereas urokinase does not bind. Accordingly, the X-Y-argininal ligands selectively bind proteinases of identical primary binding site specificity to arginine, but different secondary site specificity in -X-Y-. The selectivity is due to an amplification of peptide binding specificity caused by the transition-state analog properties of the ligands. While the affinity constants between peptide aldehyde and proteinase approach those of antibody-antigen interactions, the elution with semicarbazide (aldehyde-trapping reagent) buffers easily remove tightly bound proteinases without proteinase inhibitors or denaturation. Conditions for the binding and elution of proteinases, methods of regeneration and other characteristics of the resins are described.

Mouse plasma trypsin inhibitors: inhibitory spectrum of contrapsin and alpha-1-antitrypsin

We have studied the effects of murine alpha-1-antitrypsin and contrapsin, a new trypsin inhibitor (Takahara, H. and Sinohara, H. (1982) J. Biol. Chem. 257, in press), on several serine proteases participating in blood clotting, fibrinolysis, kinin generation, and complement activation. Bovine plasmin and human plasma kallikrein were inactivated by contrapsin but not by alpha-1-antitrypsin, whereas bovine alpha-thrombin and porcine pancreas kallikrein were inhibited by alpha-1-antitrypsin but not by contrapsin. Heparin protected thrombin from inactivation by alpha-1-antitrypsin. Both inhibitors had virtually no effects on canine C1 esterase.

Evidence for a subset of rheumatoid factors that cross-react with DNA-histone and have a distinct cross-idiotype

Cross-reactivity of a monoclonal rheumatoid factor with an antigen present on IgG and DNA-nucleoprotein was demonstrated, and evidence presented that the combining site of the antibody was involved in the reaction. The antigen on the DNA-nucleoprotein was shown to involve both DNA and histone fraction H2A + H2B and was trypsin sensitive. The relative binding affinity of the antibody appeared to be greater for IgG than the DNA-histone antigen. Similar polyclonal cross-reactive rheumatoid factors were found in a variety of diseases. A high incidence was found among patients with rheumatoid arthritis and mixed connective tissue disease. None were detected in patients with systemic lupus erythematosus and idiopathic cryoglobulinemia. Studies on one representative isolated polyclonal rheumatoid factor demonstrated the same reactivity with DNA-histone H2A + H2B as the monoclonal antibody. Cross-idiotype studies using antigen-binding inhibition methods demonstrated the same cross-idiotype on the polyclonal and the monoclonal rheumatoid factor which reacted with DNA-histone. This cross-idiotype was shown to be distinct from the cross-idiotypes previously demonstrated on monoclonal IgM proteins with anti-gamma-globulin activity.

Studies on circulating soluble immune complexes of the liver disease. 1. Inhibition assay of polyclonal rheumatoid factor binding to IgG-sepharose

Polyclonal rheumatoid factor (pRF) was isolated from sera seropositive for RF and it was radioiodinated with lactoperoxidase method. Using the 125I-pRF and IgG-p-azobenzamidoethyl Sepharose 6B, a competitive inhibition radioassay for detecting immune complexes is described. The assay can be performed in 90 min utilizing 10 microliter of serum with good reproducibility and endogenous RF in test serum did not interfere the reaction. The test can detect complexes nearly to 8s and as low as 0.1 microgram/ml of aggregated human IgG. Decomplementation by heating test sera is unnecessary. The assay was performed at 4 degrees C but less inhibition activity was obtained when it was carried out at 24 degrees C.