Features of humoral immunity in cows infected with the leukaemia virus

The article presents the results of studying the dynamics of the formation of antibodies and immune complexes, reveals the prospects for improving the early diagnosis of cattle leukaemia. Studies were conducted for 6 months on an experimental group of animals consisting of 12 cows. The titers of free and bound antibodies in blood serum and milk were determined by enzyme-linked immunosorbent assay. The results of studies showing that changes in titers of anti-leukaemia antibodies in the blood serum of cows naturally infected with BLV (bovine leukaemia virus) are significantly different from experimental infection data are adduced. In cows infected with BLV, there is no definite relationship between antibody titers in milk and in blood serum.  With sufficiently high titers of serum antibodies, antibody titers in milk can be minimal for the same cows; conversely, with low titers of serum antibodies, there can be high antibody titers in milk.  In the titers of antibodies free and bound in the immune complexes in blood serum with the development of the disease, a certain dependence is traced. With a decrease in titers of free antibodies, in most cases, an increase in titers of “bound” antibodies is observed, i.e., the degree of formation of circulating immune complexes (CECs) increases. There is no clearly defined dependence in the dynamics of changes in titers free and bound in immune complexes of antibodies in milk samples. They can remain at the same level for a long time, both at low and rather high levels.