This work aimed to evaluate the role of the spleen in storage and reactivation of the memory B cells, represented by IgM positive cells and the systemic production of sheep antibodies anti-red cell in Nile tilapia (Oreochromis niloticus). Two groups were established: the memory group, containing fish previously immunized with a 2,5% sheep anti-red cell, to generate the immune memory; and the naive group, containing fish that received a 0,65% saline solution. After 32 days, both groups were subjected to a new dose of the same antigen at the same concentration, volume, and inoculation via. The memory clones reactivation was correlated to the increase of the IgM positive cells in the spleen in the memory group at 0 day. The memory group showed an increase in the absolute number of lymphocytes at 21 days and an increase in the antibodies at 14 days after inoculation when compared to the naive group. The results suggest that the spleen may be a storage and reactivation place of memory B cells in Nile tilapia.
teleost; immunology; immunoglobulin M; vaccine