Shared idiotypic determinant in mono- and polyclonal anti-phospholipid antibodies with lupus anticoagulant activity

Antibody response to long-term and high-dose mould-exposed sawmill workers

Exposure to moulds is thought to cause adverse health effects ranging from vague subjective symptoms to allergy and respiratory diseases. Until now, most studies have been emphasizing low levels of exposure. In Norwegian sawmills during the 1980s, extensively high spore counts up to 10(7) spores/m3 air were reported. By using serum samples obtained from sawmill workers during that period, in addition to control sera, we studied the antibody response of all classes and IgG subclasses to Rhizopus microsporus at different levels of exposure. Antigen specificity was further studied by Western blotting. Exposure to R. microsporus was accompanied by R. microsporus-specific antibody production against a wide range of antigenic components most likely of both protein and carbohydrate nature. Increasing levels of mould-specific IgG1, IgG2, IgG4 and IgA antibodies were associated with increased exposure, while the highest levels of exposure were associated with a somewhat reduced level of mould-specific IgE antibodies. In conclusion, the present study strongly suggests that high mould exposure can induce a strong IgG and IgA response in a dose-dependent manner.

Increased thromboembolic incidence in anti-cardiolipin-positive patients with malignancy

This study was undertaken to determine the prevalence of anti-cardiolipin antibodies (ACLAs) in patients with malignancy and to investigate a possible association of ACLAs with thromboembolic events in such patients. The study included 216 patients with solid and non-solid malignancies and an age-matched control group of 88 healthy subjects. ACLA levels were measured and related to thromboembolic phenomena (diagnosed by imaging methods) that occurred within 12 months of the diagnosis of cancer. Forty-seven patients (approximately 22%) with cancer were ACLA positive as compared with only three subjects (approximately 3%) in the control group (P < 0.0001). The ACLA-positive cancer patients had a significantly higher rate of thromboembolic events than ACLA-negative cancer patients: 13 of 47 (28%) vs 24 of 169 (14%), respectively (P < 0.05). High titres of either IgG-ACLA or IgM-ACLA were found in 10 out of 13 ACLA-positive cancer patients with thrombotic complications, but in only 2 out of 34 cancer ACLA-positive patients without thromboembolic events (P < 0.0001). In four cancer patients in whom ACLA levels were followed ACLA decreased after successful surgery/chemotherapy treatment and remained negative and thromboembolic free for 12 months of follow-up. Patients with malignancies show an increased prevalence of ACLA. Furthermore, ACLA-positive patients, mainly those with high titres, are much more prone to thromboembolic events.

A quantitative, semi-automated and computer-assisted test for lupus anticoagulant

We describe the design of a quantitative test for lupus anticoagulants (LA), based on the Activated Partial Thromboplastin Time (APTT) and the Russell Viper Venom Time (RVVT). In this assay system, test plasmas mixed 1:1 with a pooled normal plasma (NP) are tested at a low as well as a high cephalin concentration, using an ACL 3000 automated clot timer. The ratio of these two clotting times, divided by the corresponding ratio for the NP, was defined as the Lupus Ratio (LR) and calculated by means of a computer program. The frequency distribution of the LR in a reference population of 150 healthy individuals was determined, and the 97.5 percentile was defined as the upper reference limit and allocated the value one Lupus Anticoagulant Unit (LA-U). Using dilutions of one strong LA positive plasma, standard curves for LA-U determination were constructed for the APTT as well as the RVVT based test, and fitted with a log-logit computer model. The sensitivity of the tests was comparable to that of the Kaolin Clotting Time (KCT). Plasma samples from warfarin treated patients were uniformly negative, while most heparin-containing plasmas were positive in both tests. Plasmas deficient in Factors V, VIII and IX were negative, whereas one Factor VIII-inhibitor containing plasma was positive in the APTT and negative in the RVVT. The present work shows that it is possible to adapt the APPT as well as the RVVT for LA quantification. With an automated clot timer and computer based calculation of results, the assays are simple and reproducible and have a high sensitivity and specificity.

Human IgG3 is decreased and IgG1, IgG2 and IgG4 are unchanged in molecular size by mild reduction and reoxidation without any major change in effector functions

Purified proteins of the four human IgG subclasses were reduced under neutral conditions to break the interchain S-S bonds, followed by dialysis to allow reformation of S-S bonds (pr/o treatment). The IgG1, IgG2 and IgG4 proteins apparently reformed native molecules by pr/o treatment, while IgG3 formed molecules with significantly smaller size, as measured by HPLC gel filtration, compared to the autologous native proteins. The degree of shrinking of the pr/o IgG3 molecules varied and was most pronounced at low protein concn. In addition, the temp and the concn of reducing agent during the pr/o treatment had some influence on the molecular size. The effect is probably due to a conformational change of the 62 amino acid long hinge of IgG3. The effector activity of pr/o IgG2 and pr/o IgG3 was studied by employing chimeric, mouse V and human C regions, monoclonal antibodies with the same NIP-binding properties. Thus, the interaction between IgG and the complement system was unchanged both for pr/o IgG2 and pr/o IgG3, while the Fc-receptor-mediated antibody-dependent cellular cytotoxicity (ADCC) was depressed to the same degree for both pr/o IgG2 and pr/o IgG3. Conclusively, the alteration of the conformation of the IgG3 molecule by pr/o treatment had no major influence on its effector functions.