Abstract
dourine is diagnosed using serological tests such as the classical complement fixation test (CFT), the horse complement fixation test (HCFT). We have recently developed a long-term variant of HCFT - horse complement long fixation (HCLFT). The main component that directly affects the sensitivity of the above tests is the trypanosomal antigen. From the correct definition of the working titer of the latter depends on the clarity of setting and the course of reactions. The aim of our work was to determine the working titer of the trypanosomal antigen in CFT, HCFT and HCLFT. The working antigen titer for each serological reaction remains stable after its determination. This indicator was determined by the checkerboard method of titration of the antigen and positive serum. We have established the working titer of the antigen in the antigenic unit (AU). At the same time, we took 1,5 AU for the working titer of the trypanosome antigen. It was 1:20 in CFT, 1:100 in HCFT and 1:150 in HCLFT. It is these dilutions of the antigen that we will use when setting up the above tests.