The identification of red cell antibodies as IgM or IgG immunoglobulins often provides useful information in blood banking (Hasekura, 1974; Moor and Steane, 1976). IgM immunoglobulin may be inactivated by treatment with sulphydryl compounds such as 2-mercaptoethanol (2-ME). The drawbacks are its obnoxious odour and the need for dialysis of the specimen in some cases (Pirofsky and Rosner, 1974; Moor and Steane, 1976 (Webb, 1972).DTT was obtained from Sigma (St. Louis, Missouri). The procedure used was essentially the same as that described by Pirofsky and Rosner. Briefly, 0O01 M DTT is prepared in pH 7-4 phosphate buffered saline (PBS). After addition of 025 ml DTT in PBS to 025 ml of test serum, resulting in a final concentration of 0O005 M DTT, the mixture is incubated at 370C for two hours. For evaluation of the optimal conditions of DTT inactivation of IgM antibodies, changes of molarity of DTT were made by appropriately diluting the stock solution in phosphate buffered saline. The pH of the solution was altered by changing appropriately the ratio of Na2HPO and KH2PO4.The titration of antibodies was scored according to the procedure set out by the American Association of Blood Banks 1974. ResultsThe effects of incubation time, incubation temperature, and concentrations and pH of DTT were evaluated by using high-titre group 0 sera in the saline phase. The pretreatment titration of the sera ranged from 32 to 128. The effects of incubation temperature and incubation time on the reduction of titration scores by DTT are shown in Figure 1. A marked reduction was seen after a 15-minute 1152 copyright.