Antibody response to mycobacterial hsp65 (Bhsp65) of Celastrus-fed Lewis (LEW) rats. LEW rats (n = 4 to 6) were fed either Celastrus (3 g/kg) or water as described in the legend to Figure 1. Blood samples were collected from LEW rats immediately before (preimmune serum; day 0) challenge with M. tuberculosis H37Ra (Mtb; 1 mg/rat) as well as at different time points thereafter (days 10, 18 and 24). These sera were tested separately at different dilutions (1:50 to 1:8,100) by ELISA for total immunoglobulin against Bhsp65. The results are expressed as optical density (O.D.) at 540 nm (mean + standard error of the mean). At one representative concentration of sera (for example, 1:100 dilution), the level of antibody response to Bhsp65 in Celastrus-fed rats was significantly higher than that of water-fed rats on days 18 and 24 (**p < 0.01 each).