EN
Sera of 51 cows, including 8 cows with a nodular form of epizootic bovine leukemia, from cowsheds of a high percent of BLV infection (more than 80%) and their foetuses have been examined. The presence and content of IgG, IgM and IgA in sera of cows and their foetuses was determined by the method of a radial single immunodiffusion using standard kits (Miles). The highest content of IgG (1946 mg/100 ml) was noted in sera of cows with a subclinic form of leukemia and the lowest one (1579 mg/100 ml) in seropositive cows. However, these differences were not statistically significant. The level of serum IgM was significantly higher in healthy cows (536 mg/100 ml) and in sera of seropositive cows (486 mg/100 ml) comparing to cows with a permanent lymphocytosis (419 mg/100 ml) and with histopathological lesions (446 mg/100 ml). The content of IgA ranged in all groups from 57 to 60 mg/100 ml. In a group of foetuses from cows with a permanent lymphocytosis the level of serum IgM was higher (13.9 mg/100 ml) comparing to other groups (16.5—17.6 mg/100 ml). A slightly higher level of all immunoglobulin classes was observed in seropositive foetuses against EBL.