A solid-phase erythrocyte adherence assay has been developed for the serological detection of reagin antibodies in syphilis. CaptureS (Immucor, Inc., Norcross, Ga.) is a nontreponemal, qualitative screening test for the detection of immunoglobulin G (IgG) and IgM antilipid antibodies in serum or plasma samples from blood donors. The CaptureS assay utilizes a modified Venereal Disease Research Laboratory antigen bound to microtitration wells and anti-IgG-plus anti-IgM-coated indicator erythrocytes as the detection system. The CaptureS assay was evaluated at six separate sites on 10,942 specimens. For patient samples of clinically diagnosed syphilis categories (n ‫؍‬ 366), the CaptureS assay yielded a sensitivity of 80.7% versus 80.3% for the rapid plasma reagin (RPR) card test (Becton Dickinson Microbiology Systems, Cockeysville, Md.). In comparative experiments on patient and donor samples (n ‫؍‬ 10,222), the CaptureS assay demonstrated a sensitivity of 94% compared to 91.2% for the RPR card test. The CaptureS and RPR card tests produced essentially equivalent specificities of 99.2% and 99.3%, respectively, for this sample population. For five test sites, the CaptureS and RPR card test demonstrated a 98.3% agreement (10,085 of 10,264) of test results. These evaluations indicate that the CaptureS compares favorably to the RPR card test in assay sensitivity and specificity, with the added benefits of ease of use, accommodation of high-volume testing, and potential for automation.

The ability of fresh human amnion to bind and internalize horseradish peroxidase-labeled IgG (IgG-HRP) was examined in an in vitro Ussing chamber system. The amnion demonstrated unique cell membrane receptors for the Fc portion of IgG molecules (Fc gamma R). The Fc gamma R exhibit exquisite specificity and affinity for IgG monomers as demonstrated by staining with labeled IgG. Labeled IgA, IgM, F(ab')2 fragments of IgG, aggregated IgG, and antigen-antibody complexes all failed to bind to the amnionic epithelial cells. Binding was only minimally affected by changes in ionic strength or pH when viewed at the light microscopic level. The Fc gamma R are located on both the apical and basal cell membranes. The binding of IgG-HRP to the amnion cell membrane was detectable within 1 min, and internalization of the ligand occurred within 5 min. No binding of IgG-HRP was observed following treatment of the membrane with 0.25% trypsin for 30 min at room temperature. Incubation of the amnion at 4 degrees C or in the presence of colchicine or cytochalasin D prevented internalization of the IgG-HRP. These experiments demonstrate Fc gamma R on human amnionic epithelial cells that both bind and internalize IgG, thus allowing the amnion to be used as a model system for studying IgG transport.

A solid-phase red cell adherence assay was used to demonstrate the specific inhibitory effect of seven species of Trimeresurus snake venom on the binding of HPA-1a-and HPA-1b-specific platelet antibodies. Trimeresurus venom did not inhibit the binding of HLA-, HPA-3a-, HPA-3b-, HPA-4a-, HPA-5a-, and HPA-5b-specific platelet antibodies. Venom from other genera of snakes, including representatives from Agkistrodon,

Recent technological advances in the immobilization and drying of red cell monolayers for use in solid phase red cell adherence (SPRCA) assays have resulted in the development of reagent red cells for antibody screening and identification that are stable at mom temperature. Panels consisting of twelve different RBC samples dried onto individual microplate wells were evaluated with 176 samples whose antibody specificities had previously been determined by conventional hemagglutination techniques. Identification tests performed with dried SPRCA panels proved to be more sensitive and less time consuming than hemagglutination tests. The red cell antigens of dried membranes were shown to be stable and reactive following storage for 120 days at mom temperature.