Evaluation of adenosine deaminase activity in the Mycobacterium tuberculosis culture supernatants

Background. Adenosine deaminase (ADA) catalyzes hydrolytic and irreversible deamination of deoxyadenosine into deoxyinosine and of adenosine into inosine, and is related to lymphocytic proliferation and differentiation. The measurement of ADA activity in body fluids is a useful tool in the evaluation of mycobacterial infections. Elevated ADA activity has, been found in pleural effusions of patients with pleural tuberculosis relative to those from patients with nontuberculous pleural diseases, and is mainly associated with cellular host factors such as monocyte-macrophages or lymphocytes. In contrast, there is little information about ADA activity measurement in mycobacteria culture supernatants. Methods. We evaluated ADA activity as described by Giusti in the culture supernatants of eight Mycobacterium tuberculosis isolates. Results. Mycobacteria culture supernatants did not display any ADA activity. Conclusions. This results supports the notion that Mycobacterium tuberculosis is not the source of ADA activity. However, increased ADA activity in biological fluids from tuberculosis patients might be due to the interaction of the mycobacterium with host factors

On the correct determination of reference values for serum antibodies against pigeon serum antigen using a group of healthy blood donors

An ensymatic immunoassay was developed in order to evaluate the statistical distribution of IgG serum antibodies against pooled pigeon ser antigen in 102 healthy blood donors (HBD). A non-normal distribution was obtained as demonstrated by abnormal values of skewness (2.02) and kurtosis (6.50). A cut-off point (0.120) was determined from the mean plus 2 standard derivations of the optical density values obtained in the HBD group. This value was able to segregate 94 percent of subjects. However, when calculation of the mean less 2 SD was performed to delimit 95 percent of the samples, an aberrant negative value was obtained. In contrast, when the nonparametric method of percentile calculation was applied, an optical density value of 0.130 discriminated 97.5 percent of samples. In addition, the interval between p97.5 and p2.5 delimited 95 percent of samples. We conclude that when reference values and cut-off point are determined from an enzymatic immunoassay, careful analysis of the statistical distribution of reference values is necesary in order to avoid the inappropiated in this study for antibodies against pigeon serum antigens