Serological and immunochemical assessment of anti-complement monoclonal antibodies

Abstract

The antiglobulin test for the detection of red cell antibodies is included in almost all regimes for pretransfusion testing. The polyspecific reagents produced for this purpose usually contain anti-complement antibodies to enable the detection of certain complement-binding antibodies of clinical significance. In addition the diagnosis of Cold Auto-immune Haemolytic Anaemia (CHAD) is supported by a positive direct antiglobulin test (DAT) using a reagent containing anti-C3d. Anti-C3d is therefore a necessary component of a polyspecific reagent. Unfortunately, if the strength of anti-C3d from a polyclonal reagent is optimal, it tends to be associated with unwanted reactions with red cells that have been stored in serum or plasma [9]. Even when apparently pure antigen is used for immunization, animals may make large amounts of antibody against minor contaminants. The specificity and potency varies from one animal and even one breed to the next, making reagent production both time consuming and uncertain.

In recent years several monoclonal antibodies have been produced with a specificity for complement components or for certain fragments. These include an antibody to C3 which reacts with a C3d epitope which appears to be exposed on all complement-coated red cells encountered in blood transfusion serology, NBTS-BRIC 8 (Holt et al., 1985) [10] and an anti-C3c, WM1 [17]. Chaplin et al., 1980) [2, 3] has reported a comparative study of four monoclonal anti-C3d and a series of 32 antibodies to C3c and C3d have recently been described and detailed serological and immunochemical investigations reported [5]. Some antibodies react with fragments such as C3g (Lachmann et al., 1980) [11] which are not always present or exposed on complement-coated red cells.

In the present study the serological and immunochemical properties of antibodies 12 W 1, 12 W 2, 12 W 3, 12 W 4, 12 W 5 and 9 W 14 were investigated.