Quantitation of rheumatoid factor activity by nephelometry

CYP1A2 genotype and rheumatoid arthritis in Koreans

Cytochrome P540 (CYP) 1A2 plays a role in the production of reactive oxygen species (ROS), which have been implicated in the development of rheumatoid arthritis (RA). The objective of this study was to investigate the association between a common polymorphism in the CYP1A2 gene with risk and severity of RA in a Korean population. Cases (n = 1321) with RA and controls (n = 1037) were genotyped for the CYP1A2 -163 A>C polymorphism by real-time PCR. HLA-DRB1 typing and further subtyping of all alleles was performed by PCR, sequence-specific oligonucleotide probe hybridization and direct DNA sequencing analysis. The odds ratio (OR) [(95% confidence interval (CI)] of RA associated with the low inducible C allele was 1.11 (0.80-1.55) among non-shared epitope (SE) carriers, 0.82 (0.56-1.20) among heterozygotes and 0.32 (0.10-1.04) among individuals homozygous for the SE (P = 0.03 for CYP1A2-SE interaction). A protective effect of the low inducibility CYP1A2 C allele among carriers of the SE suggests that a product of CYP1A2-mediated metabolism, such as ROS, may be involved in the development of RA.

Catalase and PPARgamma2 genotype and risk of rheumatoid arthritis in Koreans

Catalase (CAT) and peroxisome proliferator activated receptor-gamma2 (PPARgamma2) are important regulators of oxidative stress and inflammation, and may contribute to the development of rheumatoid arthritis (RA). We investigated the association between CAT and PPARgamma2 genotypes and risk and severity of RA using 474 cases and 400 controls. Genotyping for the -262C-->T polymorphism of CAT and the Pro12Ala polymorphism of PPARgamma2 was performed by PCR-RFLP analysis. Severity of RA was assessed by the anatomical stage according to Steinbrocker, and a Korean language version of a Health Assessment Questionnaire (KHAQ). No association was observed between CAT and PPARgamma2 genotypes and risk of RA. Our results suggest that genetic polymorphisms of CAT and PPARgamma2 do not play a significant role in the susceptibility to RA among Koreans.

Quantitative determination of IgM-rheumatoid factor by enzyme immunoassay--standardization using a serum from a rheumatoid arthritis patient

A method to standardize the quantitation of IgM-rheumatoid factor (RF) by enzymeimmunoassay (EIA) is presented. Serially diluted sera from rheumatoid arthritis patients were added to immobilized human IgG, and bound IgM-RF was detected by addition of horseradish peroxidase labeled anti-human IgM (HRPOaM). The concentration of IgM-RF which produced half of the maximal absorbance at 492 nm given by a saturating concentration of IgM-RF in the EIA plate, was defined as 1 U/ml. The IgM-RF values of test samples were measured as the dilution of the sample which provided half-maximal absorbance. The IgM-RF values determined by this method coincided with those determined by referring to a standard curve made from a serum containing known amounts of IgM-RF. Differences in IgM-RF values, which were caused by varying preparations of horseradish peroxidase anti-IgM (HRPOaM) were corrected for the binding capacity of each preparation to various concentrations of human IgM adherent to the plate. The IgM-RF values determined by this method correlated well with the RF values determined by latex photometric immunoassay (r = 0.956, p less than 0.001). IgM-RF values determined by EIA were converted into WHO-units by an empirical formula described. The data observed suggest that the method here reported can standardize IgM-RF values obtained by EIA.

Low-dose D-penicillamine therapy in rheumatoid arthritis. A controlled, double-blind clinical trial

Two hundred twenty-five patients with active severe rheumatoid arthritis were admitted to a multiclinic, controlled, double-blind trial comparing the use of 500 mg D-penicillamine per day, 125 mg D-penicillamine per day, and placebo. One hundred seventy-one patients completed at least 30 weeks of therapy. The 500 mg D-penicillamine group demonstrated statistically significant improvement over the placebo group in grip strength, average circumference of swollen proximal interphalangeal joints, and patient assessment. While the trend was for greater improvement with the larger dose of D-penicillamine, there was no statistically significant difference among the 3 groups in duration of morning stiffness, walking time, physician's assessment, number of swollen joints, or scores for tender and swollen joints. The slight increase in efficacy of higher dose D-penicillamine was associated with increased toxicity.

Quantitation of serum immunoglobulins

This article reviews critically the current "state of the art" in the quantitation of immunoglobulins in serum and other body fluids. The methodologies reviewed include (a) those occurring in solution, for example, automated immunoprecipitin and laser nephelometric techniques, rate analysis techniques and radioimmunoassays; (b) techniques involving radial diffusion in agarose gels, with and without secondary development steps; and (c) those techniques involving solid supports, such as fluoroimmunometric assays and solid phase radioimmunoassays. The theory of each technique is presented with an analysis of the strengths and weaknesses, particularly sources of error, and the techniques are compared in terms of accuracy, precision, sensitivity, test cost, equipment cost, feasibility for use in different laboratory settings, and ease of handling. Problems associated with the antisera used, with standards, and with quality controls are discussed and solutions suggested.