Autologous red cell agglutination test for antibodies to feline immunodeficiency virus

The T-lymphotropic lentivirus, feline immunodeficiency virus (FIV) is now recognised as a major viral pathogen affecting domestic cat populations worldwide. A rapid, autologous red cell agglutination test for antibodies to FIV has been developed. A synthetic peptide analog corresponding to the immunodominant epitope within the FIV transmembrane glycoprotein gp40 residues (680-715) KVEAMEKFLYTAFAMQELGC (Acm)NQNQFFK(BrAc)KIPLELWTR was conjugated to an anti-feline erythrocyte antibody using a thio-ether linkage. Within 3 min of adding this reagent to 20 μl of whole blood, circulating antibody to the peptide epitope caused agglutination of the red blood cells. The performance of this simple test is comparable with the two commercially available enzyme immunoassay (EIA) kits and an EIA based on this peptide. A variant of the gp40 (680-715) peptide corresponding to the FIV, PPR strain gp40 (678-716) sequence was also synthesised and no difference in reactivity was observed in an EIA on 211 seropositive samples, indicating that the peptide-based test may be applicable to other known strains of the virus

Death of cells by apoptosis following attachment of specifically allergized lymphocytes in vitro

A low rate of spontaneous cell death by apoptosis was found in a DBA/2 mouse mastocytoma growing in culture. It was not significantly altered by addition of splenic lymphocytes from normal C57BL mice, but was massively enhanced by lymphocytes from mice previously immunized against the tumor. Cells showing ultrastructural changes of early apoptosis in the latter experiments had lymphocytes firmly attached to their surfaces, suggesting that cellular immune attack induces apoptosis directly: the cell budding to produce membrane-bounded fragments with well preserved organelles characteristic of the later stages of the process was associated with lymphocyte detachment. These cell fragments or apoptotic bodies were not phagocytosed by viable cells as they are when apoptosis takes place in tissues, and underwent secondary degeneration with ballooning of organelles and rupture of membranes while still suspended in the medium. The major wave of lymphocyte-induced apoptosis occurred within the first 3 h of incubation. The number of well preserved apoptic bodies reached a peak at 1 1/2 hr and thereafter declined, whereas cell debris increased progressively. The maximum rate of release of absorbed, Cr from tumour cells coincided in time with the wave of apoptosis, but difficulty in assessing the relative rates of formation and secondary degeneration of apoptotic bodies made it impossible to determine whether the release was particularly associated with one or the other of these processes. That cellular immune attack should induce a type of cell death known to occur in normal tissue has implications for the hypothesis that the immune system continuously monitors cells and eliminates those that undergo significant antigenic change

Measurement of crosslinked fibrin degradation products. An immunoassay using monoclonal antibodies

We have prepared a monoclonal antibody which recognises an antigenic determinant on D-dimer, a specific fragment resulting from the degradation of crosslinked fibrin. This antibody has been used in the development of an enzyme-linked immunoassay for D dimer and related degradation products containing crosslinked gamma-gamma chains, to provide a simple assay of circulating crosslinked fibrin degradation products suitable for clinical use. Since these crosslinked fibrin degradation products are characteristic of fibrinolysis, as distinct from fibrinogenolysis, their measurement should aid in the diagnosis, evaluation and monitoring of thrombotic and thrombolytic states. In preliminary studies, low concentrations of crosslinked fibrin derivatives were detected in normal sera. High levels were found in 30/30 patients with disseminated intravascular coagulation and in the majority of patients having deep venous thrombosis or pulmonary embolism